How To Buy Forgings

Close cooperation between buyers and producers of forgings has always been a vital part of achieving the best possible product at the best possible cost. With recent major advances in forging methods and materials improvements, this collaboration is more critical than ever before. By keeping abreast of these advances, and working closely with the forger, the engineer or buyer can ensure delivery of high-quality products with important cost savings.

 

Despite its long history and the many technological developments that have taken place in recent years, forging still involves a good deal of artistry. Even as product designers and industrial buyers learn more about shaping of metals, there is still much to be gained from bringing the forger into the design and specification phases of product development.

 

Of course, such basic questions as whether a given part can or should be forged must be addressed at an early stage. There are many instances when any of several

processes can be used to produce the component in question. Once it has been determined that a product or component requires the strength, toughness, dimensional accuracy and overall integrity of forging, there is still the question of which forging process - open die, impression die, ring rolling, etc. – is most appropriate. Usually, this decision is straightforward, based on part size, configuration and quantity required. However, to help in those situations when the choice is not so clear cut, the forging buyer should have at least a general knowledge of methods and equipment used in the industry.

 

Besides a general knowledge of forging, the buyer should also have a clear idea of what he or she specifically requires and how readily his or her needs can be met by individual forgers. Capabilities can vary dramatically from one company to another.

 

For instance:

--Does the forger have experience in applications similar to the one being considered?

--Is design assistance offered?

--Does the forger have the equipment required to produce the part?

--Is the forger able to provide related services like heat treating, machining, testing and so on?

--Is the forger accustomed to producing the volume required?

--Does the company specialize in long runs, short runs or quick delivery?

 

The answer to these and other questions will help narrow the field to a few qualified forgers. Then, the buyer can begin to take advantage of the valuable technical and design assistance available from these forging experts.

 

THE DESIGN CONFERENCE

An experienced and capable forging company engineer should be able to make design suggestions to consolidate components, simplify processing, reduce required machining, speed delivery and so on. It may be possible to achieve forging’s high level performance benefits without significantly increasing material or

production costs over those associated with other processes. The key is to get the forger involved early. The benefit derived from consultation will vary with the complexity of the part and the forging process involved. For instance, impression die forgings may benefit somewhat more dramatically than open die products. However, the ideal first step toward getting the most from a forged part is to form a team consisting of the product designer, the purchasing manager and, possibly, a quality-control or manufacturing representative. Then this team should sit down with a technical representative of the forging company while the product or component design is still being evaluated. The focal point in these early meetings with candidate forgers should be an engineering drawing. The part print should be fully detailed, showing finished dimensions and tolerances. If the forging is to be delivered in a rough-machined or asforged state, the required machining envelope should be clearly specified. In many cases, it can be advantageous to provide a drawing that shows how the forged part will mate with other components in the finished assembly. Another critical part of these early design meetings should be the service requirements of the application. The forger needs complete information

on how the forging will be used, the operating environment, and critical mechanical properties. A thorough understanding of service stresses - load-bearing, power transmitting, impact, hydraulic pressure, high or low temperatures, corrosive conditions - and the stress location can allow the forging engineer to make design and process suggestions that can result in an improved product and reduced manufacturing costs.

 

For instance:

--Material Selection...Often, alternative carbon- and alloy-steel grades can produce similar mechanical properties, depending on forging design, heat treatment, and so forth. Specifying property levels beyond those actually required by the application can significantly increase costs. The best economy is achieved when tensile, hardness, impact and other mechanical properties are realistically based on the service requirements of the component being designed. Once these realistic property levels are established, the forger can help select one material from among the alternatives to achieve the optimum combination of performance, forgeability, heat treatability, machinability and economy.

 

--Part Configuration...Special performing operations, reheats or additional dies and equipment may or may not be required to achieve the specified part configuration and the desired grain flow pattern. Almost always, a knowledgeable forger can work with a product design and achieve material and production economies with no loss of part performance. Sometimes, slight changes in part shapes can simplify forging requirements, reduce die costs, and speed production. The forging engineer studies a new design from the standpoint of its tooling and processing requirements. Reduced draft angles or sharper radii, for instance, can sometimes

reduce machining requirements without affecting part function. If a simpler die can be used or if the parting line can be adjusted to allow use of a flat top die, it may be possible to produce the part more economically.

 

--Dimensional Tolerances...The ability of forgers today to produce asforged shapes to tight tolerances is improving, and most companies are striving to develop their net- and near-net-shape forging capabilities. At present, however, there is some considerable cost involved in holding tight as-forged tolerances. The wise buyer will ask the forger to help evaluate the trade-offs between reduced machining and increased die and processing costs. In open die forging, particularly nearly all forgings require some machining. Determining where and how much machining stock “envelope” should be specified is a complex decision best made in concert with the forger.

 

But no matter what tolerances are set, it is important to include them along with all dimensions of the part drawing given to the forging engineer. Based on this information, and on his or her experience and the experience of the supplier, the forger can accept or request modification to the specifications to achieve more

cost-effective production.

 

--Applying Guidelines...Over the years, the forging industry has developed a system of dimensional tolerance guidelines that set limits on size (length, width and thickness), die match and straightness. Guidelines for impression die applications, for instance, are found in the Forging Industry Association’s Tolerances for

 

Impression Die Forgings, Hammer, Press and Upsetter.

Standards also have been developed to apply to such material considerations as chemistry, strength, ductility, impact resistance, conductivity, soundness and grain flow. These have been published by such organizations as ASTM, SAE, and the American Standards Association. Unless there is a good reason to specify a special material or tighter tolerance controls, it is best to follow the established standards to avoid additional costs.

 

--Surface Finishing...Most forging companies have machining capabilities and some offer extensive finishing services. Many buyers specify that rough machining be done by the forger so that any surface imperfections will be discovered before the parts are shipped. And there is a growing trend toward specifying that the forger also do finish machining, for reasons of economy and to isolate responsibility. The buyer gets a finished, ready-to-install component. Intermediate steps in production are left to the forger. With the added responsibility, the forger gains some flexibility that can result in overall savings for the buyer. Armed with a drawing showing finished dimensions and tolerances, the forger can design an ideal forging around the finished part. The parting line can be positioned for maximum efficiency. The chief benefit, however, is that the machining envelope can sometimes be reduced to save material and machining time.

 

--Inspection and Testing...Only those tests needed to establish the mechanical properties and quality required for reliable performance should be specified to minimize the costs involved. While the buyer will normally specify the type of test and acceptance levels required for a forging, the forger can offer good advice on appropriate testing. Tests on representative bar samples are relatively simple. When the specification requires that additional tests be made on the forging itself, costs increase. Non-destructive testing - ultrasonic and magnetic particle inspection - is becoming increasingly important for critical service applications like generator or turbine rotor shafts. Because these tests can be time-consuming and expensive, however, they should be required only when absolutely necessary.

Statistical process/quality control techniques are being applied in many forge shops. Such capabilities may reduce the need for some of the costly testing of individual forgings.

 

--Delivery...While not necessarily important in early design discussions, it is helpful to discuss production volumes and anticipated shipping schedules with the prospective forger. This information allows him or her to take these factors into consideration when making tooling decisions. In addition, production-run setup and

material acquisition requirements will vary with anticipated volume.

 

Substantial reductions in material and production costs are attainable through advance planning. And it is almost always more economical to forge and ship a quantity of parts at one time, rather than shipping to a monthly, weekly or daily schedule. However, any economies realized through bulk handling must be achieved through Just-In-Time material- control programs. The forger usually can help reconcile these conflicting objectives.

 

ADVANCING TECHNOLOGY

Even in an industry as mature and well-established as forging, there are continual advances in processing technology and techniques. Some of the developments underway in the industry today may have an impact on the production of many forgings, while others may affect only a narrow segment of the business. No matter, it is important for the forging buyer to stay abreast of developments so as to be aware of options becoming available through advancing technology. This is another good reason to get the candidate forger involved early in product development discussions. The competent forging engineer will be able to identify situations where new technology and processing techniques can benefit the buyer’s particular project. And because capabilities vary so widely from one forging plant to another, only the forger can determine how cost-effectively a particular new or more advanced procedure can be applied in that plant.

 

Here are some areas where technology is changing the way forgings are made:

 

--Net-Shape Forging has been getting a lot of attention primarily because of the potential to dramatically reduce finishing costs. Not only should it be possible to reduce the amount of stock machined away after forging, but the costs associated with machining time will be reduced. In the industry as a whole, however, net-shape forming techniques require further refinement before they become a real alternative for the average forging buyer. That does not mean there are no benefits to be achieved by studying net-shape techniques. Given a certain latitude in material selection and in forging design, the knowledgeable forger should be able to keep

machining and associated costs to a minimum. The more input the forger has in the early stages of product development, the more likely nearnet shapes can be achieved.

 

--Microalloyed Steels have been used to reduce the need for heat treatment after forging. Small additions of vanadium, columbium and other ingredients can greatly

strengthen plain carbon grades of steel. These materials can be used to forge such parts as crankshafts, connecting rods and front axles for trucks - without the need for heat treatment. This technology is still in its infancy and not all forgers will be able to take advantage of it. But under certain circumstances, and for certain components, it may be possible to reduce or eliminate the costs associated with heat treatment. Close cooperation between forging producer and forging buyer is required to ensure that the performance properties of the finished product suit the application.

 

--CAD/CAM and Computer Control are having a dramatic effect on many industries. Forging is no exception. From quoting, to die design and production, to billet handling and presses, to heat treating and machining, the computer is affecting the way forgings are produced.

 

A SERVICE INDUSTRY The custom forge plant is essentially a service organization. One of the provided is the assistance the forger can give in the design and

development of a product to be forged. Today, competition among forgers in the global marketplace is allowing the buyer to demand – and get - ever higher levels of service from the companies vying for the business. As materials and process technologies advance, it is increasingly important for the forging buyer to involve the forger in decisions that ultimately affect the cost and performance of the part. Through close collaboration with forgers, buyers can gain the greatest benefits from forging industry innovation and can help spur further progress.

 

This article is adapted from the Forging Industry Association’s booklet “How to Buy Forgings.” FIA, formed in 1913, is the trade association for U.S. and Canadian producers of forgings. Headquartered in Cleveland, it serves 150 forging company members operating more than 200 plants. Its members account for 79% of the custom

forged products produced in North America.

 

 

Source: All metals & Forge

 

Open-Die Forgings & Rolled Rings

FORGING - THE TECHNIQUE THAT PARALLELS THE DEVELOPMENT OF MAN

 

As with the cultural history of man, the history of metals springs from the land between the Tigris and the Euphrates, one called Mesopotamia. The earliest signs of metalworking date back to about 4500 B.C.

 

The inhabitants of this fertile valley were the Sumerians. These people, a mixture of many ethnic backgrounds, were the true founders of metallurgy as we know it today.

The art of forging, shaping metal using heat and pressure, progressed until the Dark Ages; the same time that most industrial, scientific and cultural advancements halted. Before this time, possession of metals was highly regarded as a sign of wealth. The Romans even had gods dedicated to the forge, the most notable being Vulcan.

 

During the Dark Ages the production of weapons flourished. European culture and industry was severely set back due to constant wars. Yet the Iron industry remained much intact due to the need for weapons. One of the most significant developments came from the combination of the Roman discovery of water power and the forging of metals. Water power was used to operate bellows and mechanical hammers.

 

This significant discovery came into use between the 10^th and 12^th century A.D. Some water operated hammers were still being used into the 20th century. The 19th century invention of the steam engine brought us to the doorstep of modern forging as we know it. Of course, to follow was the harnessing of electrical power and the development of explosive forming, which truly brought forging out of the dark ages.

 

Forging as an art form started with the desire to produce decorative objects from precious metals. Today, forging is a major world-wide industry that has significantly contributed to the development of man.

 

Source: All metals & Forge

 

Welding Tips

Tech Tips

These welding tips are meant to be helpful hints. See your equipment Owner's Manual for all safety and operational information.

• MIG Welding
• Aluminum MIG Welding
• Self-Shielded Flux Cored Welding
• TIG Welding
• Stick Welding
• Plasma Cutting
• Resistance Welding

MIG Welding

1. Keep a 1/4 ­ 3/8 in stickout (electrode extending from the tip of the contact tube.) 2. For thin metals, use a smaller diameter wire. For thicker metal use a larger wire and a larger machine. See machine recommendations for welding capacity. 3. Use the correct wire type for the base metal being welded. Use stainless steel wires for stainless steel, aluminum wires for aluminum, and steel wires for steel. 4. Use the proper shielding gas. CO2 is good for penetrating welds on steel, but may be too hot for thin metal. Use 75% Argon/25% CO2 for thinner steels. Use only Argon for aluminum. You can use a triple-mix for stainless steels (Helium + Argon + CO2). 5. For steel, there are two common wire types. Use an AWS classification ER70S-3 for all purpose, economical welding. Use ER70S-6 wire when more deoxidizers are needed for welding on dirty or rusty steel. 6. For best control of your weld bead, keep the wire directed at the leading edge of the weld pool. 7. When welding out of position (vertical, horizontal, or overhead welding), keep the weld pool small for best weld bead control, and use the smallest wire diameter size you can. 8. Be sure to match your contact tube, gun liner, and drive rolls to the wire size you are using. 9. Clean the gun liner and drive rolls occasionally, and keep the gun nozzle clean of spatter. Replace the contact tip if blocked or feeding poorly. 10. Keep the gun straight as possible when welding, to avoid poor wire feeding. 11. Use both hands to steady the gun when you weld. Do this whenever possible. (This also applies to Stick and TIG welding, and plasma cutting.) 12. Keep wire feeder hub tension and drive roll pressure just tight enough to feed wire, but don¹t overtighten. 13. Keep wire in a clean, dry place when not welding, to avoid picking up contaminants that lead to poor welds. 14. Use DCEP (reverse polarity) on the power source. 15. A drag or pull gun technique will give you a bit more penetration and a narrower bead. A push gun technique will give you a bit less penetration, and a wider bead.

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Aluminum MIG Welding

1. The best feeding of wire for aluminum is done with a spool gun. If you can't use a spool gun, use the shortest gun possible and keep the gun as straight as possible. Use Argon only for shielding gas. Only use a push gun technique when welding aluminum. 2. If you are having feeding problems, one thing you can try is a contact tip that is one size bigger than your wire. 3. The most common wire type is ER4043 for all-purpose work. ER5356 is a stiffer wire (easier to feed), and is used when more rigid, higher-strength weld properties are needed. 4. Clean the aluminum before welding, to remove the oxide layer. Use a stainless steel wire brush used only for cleaning aluminum. 5. Fill the crater at the end of the weld to avoid a crack. One way to do this is to dwell in the weld pool for a second at the end of the weld. [

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Self-Shielded Flux Cored Welding

1. Use a drag (pull) gun technique. 2. Keep the wire clean and dry for best weld results. 3. The weld is similar to Stick welding, in that a layer of slag must be removed from the weld after welding. Use a chipping hammer and a wire brush. 4. Self-shielded Flux Cored does not need shielding from an external cylinder of shielding gas. (The shielding is in the wire.) This makes it good for outside work, where external shielding gas could be blown away. 5. Self-shielded Flux Cored is generally harder to accomplish on thin metals than MIG welding. [

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TIG Welding

1. Good process for thin metal ‹ very clean process producing good looking welds. 2. Use Argon shielding for steel, stainless, and aluminum. 3. Use DC-Straight Polarity (DCEN) for steel and stainless. Use AC for aluminum. 4. Always use a push technique with the TIG torch. 5. Match the tungsten electrode size with the collet size. 6. Aluminum ‹ use a pure tungsten, AWS Class EWP (green identifying band). Will form a balled-end in AC. 7. Steel and stainless steel ‹ use a 2% thoriated tungsten, AWS Class EWTH-2 (red identifying band). Prepare a pointed-end for DCEN welding. [

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Stick Welding

1. Use a drag technique for most applications. 2. Take precautions with flying materials when chipping slag. 3. Keep electrodes clean and dry ‹ follow manufacturer¹s recommendations. 4. Common steel electrodes: 5. Penetration: DCEN ‹ Least penetration, AC ‹ medium (can be more spatter also), DCEP ‹ most penetration. [

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Plasma Cutting

1. Clean, dry, oil-free air is important. 2. Stay at recommended air pressure (more air is not necessarily better!) 3. Touch torch tip gently to workpiece. 4. When initiating a cut, start on the end of material to be cut and ensure arc has completely penetrated metal before proceeding further. 5. When completing cut, pause at the end to assure severance. 6. Torch should be perpendicular to workpiece. 7. Work cable should be attached as close to workpiece cut as possible. 8. If you can see the arc coming through the bottom of the cut metal, it will eliminate guessing if your travel speed is correct. [

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Resistance Welding

1. Resistance welding is not recommended for aluminum, copper, or copper alloys. Use for steel and stainless steel only. 2. For more heat (amperage output), use shorter tongs. 3. For units without a heat control, tong length can be used for a control. For instance, for thin metals where you want less heat, longer tongs can be used. 4. Keep in mind that longer tongs can bend, and you may lose pressure at the weld. 5. For the metals being welded, make sure there is no gap between the pieces ‹ this will weaken the weld. 6. Keep the alignment of the tongs straight, so that the tips touch each other exactly. Also, maintain a proper pressure adjustment ‹ not too much or too little pressure. 7. When you need one side of the weld to have good appearance, you can flatten (machine) the tip somewhat on that side. 8. Clean the tips on a regular basis, or you will lose output (amperage). Dress the tips with a proper tip dresser. [

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content provided by Hobart Welders and Miller Electric

WELD AND WELDING SYMBOLS

Section I. PRINT READING

3-1. GENERAL

a. Drawings. Drawing or sketching is a universal language used to convey all necessary information to the individual who will fabricate or assemble an object. Prints are also used to illustrate how various equipment is operated, maintained, repaired, or lubricated. The original drawings for prints are made either by directly drawing or tracing a drawing on a translucent tracing paper or cloth using waterproof (India) ink or a special pencil. The original drawing is referred to as a tracing or master copy.

b. Reproduction Methods. Various methods of reproduction have been developed which will produce prints of different colors from the master copy.

(1) One of the first processes devised to reproduce a tracing produced white lines on a blue background, hence the term "blueprints".

(2) A patented paper identified as "BW" paper produces prints with black lines on a white background.

(3) The ammonia process, or "Ozalids", produces prints with either black, blue, or maroon lines on a white background.

(4) Vandyke paper produces a white line on a dark brown background.

(5) Other reproduction methods are the mimeograph machine, ditto machine, and photostatic process.

3-2. PARTS OF A DRAWING

a. Title Block. The title block contains the drawing number and all the information required to identify the part or assembly represented. Approved military prints will include the name and address of the Government Agency or organization preparing the drawing, the scale, the drafting record, authentication, and the date.

b. Revision Block. Each drawing has a revision block which is usually located in the upper right corner. All changes to the drawing are noted in this block. Changes are dated and identified by a number or letter. If a revision block is not used, a revised drawing may be shown by the addition of a letter to the original number.

c. Drawing Number. All drawings are identified by a drawing number. If a print has more than one sheet and each sheet has the same number, this information is included in the number block, indicating the sheet number and the number of sheets in the series.

d. Reference Numbers and Dash Numbers. Reference numbers that appear in the title block refer to other print numbers. When more than one detail is shown on a drawing, dashes and numbers are frequently used. If two parts are to be shown in one detail drawing, both prints will have the same drawing number plus a dash and an individual number such as 7873102-1 and 7873102-2.

e. Scale. The scale of the print is indicated in one of the spaces within the title block. It indicates the size of the drawing as compared with the actual size of the part. Never measure a drawing--use dimensions. The print may have been reduced in size from the original drawing.

f. Bill of Material. A special block or box on the drawing may contain a list of necessary stock to make an assembly. It also indicates the type of stock, size, and specific amount required.

3-3. CONSTRUCTION LINES

a. Full Lines (A, fig. 3-1). Full lines represent the visible edges or outlines of an object.

b. Hidden Lines (A, fig. 3-1). Hidden lines are made of short dashes which represent hidden edges of an object.

c. Center Lines (B, fig. 3-1). Center lines are made with alternating short and long dashes. A line through the center of an object is called a center line.

d. Cutting Plane Lines (B, fig. 3-1). Cutting plane lines are dashed lines, generally of the same width as the full lines, extending through the area being cut. Short solid wing lines at each end of the cutting line project at 90 degrees to that line and end in arrowheads which point in the direction of viewing. Capital letters or numerals are placed just beyond the points of the arrows to designate the section.

e. Dimension Lines (A, fig. 3-1). Dimension lines are fine full lines ending in arrowheads. They are used to indicate the measured distance between two points.

f. Extension Lines (A, fig. 3-1). Extension lines are fine lines from the outside edges or intermediate points of a drawn object. They indicate the limits of dimension lines.

g. Break Lines (C, fig. 3-1). Break lines are used to show a break in a drawing and are used when it is desired to increase the scale of a drawing of uniform cross section while showing the true size by dimension lines. There are two kinds of break lines: short break and long break. Short break lines are usually heavy, wavy, semiparallel lines cutting off the object outline across a uniform section. Long break lines are long dash parallel lines with each long dash in the line connected to the next by a "2" or sharp wave line.

Section II. WELD AND WELDING SYMBOLS

3-4. GENERAL

Welding cannot take its proper place as an engineering tool unless means are provided for conveying the information from the designer to the workmen. Welding symbols provide the means of placing complete welding information on drawings. The scheme for symbolic representation of welds on engineering drawings used in this manual is consistent with the "third angle" method of projection. This is the method predominantly used in the United States.

The joint is the basis of reference for welding symbols. The reference line of the welding symbol (fig. 3-2) is used to designate the type of weld to be made, its location, dimensions, extent, contour, and other supplementary information. Any welded joint indicated by a symbol will always have an arrow side and an other side. Accordingly, the terms arrow side, other side, and both sides are used herein to locate the weld with respect to the joint.

The tail of the symbol is used for designating the welding and cutting processes as well as the welding specifications, procedures, or the supplementary information to be used in making the weld. If a welder knows the size and type of weld, he has only part of the information necessary for making the weld. The process, identification of filler metal that is to be used, whether or not peening or root chipping is required, and other pertinent data must be related to the welder. The notation to be placed in the tail of the symbol indicating these data is to be establish by each user. If notations are not used, the tail of the symbol may be omitted.

3-5. ELMENTS OF A WELDING SYMBOL

A distinction is made between the terms "weld symbol" and "welding symbol". The weld symbol (fig. 3-3) indicates the desired type of weld. The welding symbol (fig. 3-2) is a method of representing the weld symbol on drawings. The assembled "welding symbol" consists of the following eight elements, or any of these elements as necessary: reference line, arrow, basic weld symbols, dimensions and other data, supplementary symbols, finish symbols, tail, and specification, process, or other reference. The locations of welding symbol elements with respect to each other are shown in figure 3-2.

3-6. BASIC WELD SYMBOLS

a. General. Weld symbols are used to indicate the welding processes used in metal joining operations, whether the weld is localized or "all around", whether it is a shop or field weld, and the contour of welds. These basic weld symbols are summarized below and illustrated in figure 3-3.

b. Arc and Gas Weld Symbols. See figure 3-3.

c. Resistance Weld Symbols. See figure 3-3.

d. Brazing, Forge, Thermit, Induction, and Flow Weld Symbols.

(1) These welds are indicated by using a process or specification reference in the tail of the welding symbol as shown in figure 3-4.

(2) When the use of a definite process is required (fig. 3-5), the process may be indicated by one or more of the letter designations shown in tables 3-1 and 3-2.

NOTE

Letter designations have not been assigned to arc spot, resistance spot, arc seam, resistance seam, and projection welding since the weld symbols used are adequate.

(3) When no specification, process, or other symbol, the tail may be omitted (fig. 3-6). reference is used with a welding

e. Other Common Weld Symbols. Figures 3-7 and 3-8 illustrate the weld-all-around and field weld symbol, and resistance spot and resistance seam welds.

f. Supplementary Symbols. These symbols are used in many welding processes in congestion with welding symbols and are used as shown in figure 3-3.

3-7. LOCATION SIGNIFICANCE OF ARROW

a. Fillet, Groove, Flange, Flash, and Upset welding symbols. For these symbols, the arrow connects the welding symbol reference line to one side of the joint and this side shall be considered the arrow side of the joint (fig. 3-9). The side opposite the arrow side is considered the other side of the joint (fig. 3-10).

b. Plug, Slot, Arc Spot, Arc Seam, Resistance Spot, Resistance Seam, and Projection Welding Symbols. For these symbols, the arrow connects the welding symbol reference line to the outer surface of one member of the joint at the center line of the desired weld. The member to which the arrow points is considered the arrow side member. The other member of the joint shall be considered the other side member (fig. 3-11).

c. Near Side. When a joint is depicted by a single line on the drawing and the arrow of a welding symbol is directed to this line, the arrow side of the joint is considered as the near side of the joint, in accordance with the usual conventions of drafting (fig. 3-12 and 3-13).

d. Near Member. When a joint is depicted as an area parallel to the plane of projection in a drawing and the arrow of a welding symbol is directed to that area, the arrow side member of the joint is considered as the near member of the joint, in accordance with the usual conventions of drafting (fig. 3-11).

3-8. LOCATION OF THE WELD WITH RESPECT TO JOINT

a. Arrow Side. Welds on the arrow side of the joint are shown by placing the weld symbol on the side of the reference line toward the reader (fig. 3-14).

b. Other Side. Welds on the other side of the joint are shown by placing the weld symbol on the side of the reference line away from the reader (fig. 3-15).

c. Both Sides. Welds on both sides of the joint are shown by placing weld symbols on both sides of the reference line, toward and away from the reader (fig. 3-16).

d. No Side Significance. Resistance spot, resistance seam, flash, weld symbols have no arrow side or other side significance in themselves, although supplementary symbols used in conjunction with these symbols may have such significance. For example, the flush contour symbol (fig. 3-3) is used in conjunction with the spot and seam symbols (fig. 3-17) to show that the exposed surface of one member of the joint is to be flush. Resistance spot, resistance seam, flash, and upset weld symbols shall be centered on the reference line (fig. 3-17).

3-9. REFERENCES AND GENERAL NOTES

a. Symbols With References. When a specification, process, or other reference is used with a welding symbol, the reference is placed in the tail (fig. 3-4).

b. Symbols Without References. Symbols may be used without specification, process, or other references when:

(1) A note similar to the following appears on the drawing: "Unless otherwise designated, all welds are to be made in accordance with specification no...."

(2) The welding procedure to be used is described elsewhere, such as in shop instructions and process sheets.

c. General Notes. General notes similar to the following may be placed on a drawing to provide detailed information pertaining to the predominant welds. This information need not be repeated on the symbols:

(1) "Unless otherwise indicated, all fillet welds are 5/16 in. (0.80 cm) size."

(2) "Unless otherwise indicated, root openings for all groove welds are 3/16 in. (0.48 cm)."

d. Process Indication. When use of a definite process is required, the process may be indicated by the letter designations listed in tables 3-1 and 3-2 (fig. 3-5).

e. Symbol Without a Tail. When no specification, process, or other reference is used with a welding symbol, the tail may be omitted (fig. 3-6).

3-10. WELD-ALL-AROUND AND FIELD WELD SYMBOLS

a. Welds extending completely around a joint are indicated by mans of the weld-all-around symbol (fig. 3-7). Welds that are completely around a joint which includes more than one type of weld, indicated by a combination weld symbol, are also depicted by the weld-all-around symbol. Welds completely around a joint in which the metal intersections at the points of welding are in more than one plane are also indicated by the weld-all-around symbol.

b. Field welds are welds not made in a shop or at the place of initial construction and are indicated by means of the field weld symbol (fig. 3-7).

3-11. EXTENT OF WELDING DENOTED BY SYMBOLS

a. Abrupt Changes. Symbols apply between abrupt changes in the direction of the welding or to the extent of hatching of dimension lines, except when the weld-all-around symbol (fig. 3-3) is used.

b. Hidden Joints. Welding on hidden joints may be covered when the welding is the same as that of the visible joint. The drawing indicates the presence of hidden members. If the welding on the hidden joint is different from that of the visible joint, specific information for the welding of both must be given.

3-12. LOCATION OF WELD SYMBOLS

a. Weld symbols, except resistance spot and resistance seam, must be shown only on the welding symbol reference line and not on the lines of the drawing.

b. Resistance spot and resistance seam weld symbols may be placed directly at the locations of the desired welds (fig. 3-8).

3-13. USE OF INCH, DEGREE, AND POUND MARKS

NOTE

Inch marks are used for indicating the diameter of arc spot, resistance spot, and circular projection welds, and the width of arc seam and resistance seam welds when such welds are specified by decimal dimensions.

In general, inch, degree, and pound marks may or may not be used on welding symbols, as desired.

3-14. CONSTRUCTION OF SYMBOLS

a. Fillet, bevel and J-groove, flare bevel groove, and corner flange symbols shall be shown with the perpendicular leg always to the left (fig. 3-18).

b. In a bevel or J-groove weld symbol, the arrow shall point with a definite break toward the member which is to be chamfered (fig. 3-19). In cases where the member to be chamfered is obvious, the break in the arrow may be omitted.

c. Information on welding symbols shall be placed to read from left to right along the reference line in accordance with the usual conventions of drafting (fig. 3-20).

d. For joints having more than one weld, a symbol shall be shown for each weld (fig 3-21).

e. The letters CP in the tail of the arrow indicate a complete penetration weld regardless of the type of weld or joint preparation (fig. 3-22).

f. When the basic weld symbols are inadequate to indicate the desired weld, the weld shall be shown by a cross section, detail, or other data with a reference on the welding symbol according to location specifications given in para 3-7 (fig. 3-23).

g. Two or more reference lines may be used to indicate a sequence of operations. The first operation must be shown on the reference line nearest the arrow. Subsequent operations must be shown sequentially on other reference lines (fig. 3-24). Additional reference lines may also be used to show data supplementary to welding symbol information included on the reference line nearest the arrow. Test information may be shown on a second or third line away from the arrow (fig. 3-25). When required, the weld-all-around symbol must be placed at the junction of the arrow line and reference line for each operation to which it applies (fig. 3-26). The field weld symbol may also be used in this manner.

3-15. FILLET WELDS

Dimensions of fillet welds must be shown on the same side of the reference line as the weld symbol (A, fig. 3-27).

b. When fillet welds are indicated on both sides of a joint and no general note governing the dimensions of the welds appears on the drawing, the dimensions are indicated as follows:

(1) When both welds have the same dimensions, one or both may be dimensioned (B or C, fig. 3-27).

(2) When the welds differ in dimensions, both must be dimensioned (D, fig. 3-27).

c. When fillet welds are indicated on both sides of a joint and a general note governing the dimensions of the welds appears on the drawing, neither weld need be dimensioned. However, if the dimensions of one or both welds differ from the dimensions given in the general note, both welds must be dimensioned (C or D, fig. 3-27).

3-16. SIZE OF FILLET WELDS

a. The size of a fillet weld must of a fillet weld be shown to the left of the weld symbol (A, fig. 3-27).

b. The size the fillet weld with unequal legs must be shown in parentheses to left of the weld symbol. Weld orientation is not shown by the symbol and must be shown on the drawing when necessary (E, fig. 3-27).

c. Unless otherwise indicated, the deposited fillet weld size must not be less than the size shown on the drawing.

d. When penetration for a given root opening is specified, the inspection method for determining penetration depth must be included in the applicable specification.

3-17. LENGTH OF FILLET WELDS

a. The length of a fillet weld, when indicated on the welding symbol, must be shown to the right of the weld symbol (A through D, fig. 3-27).

b. When fillet welding extends for the full distance between abrupt changes in the direction of the welding, no length dimension need be shown on the welding symbol.

c. Specific lengths of fillet welding may be indicated by symbols in conjunction with dimension lines (fig. 3-28).

3-18. EXTENT OF FILLET WELDING

a. Use one type of hatching (with or without definite lines) to show the extent of fillet welding graphically.

b. Fillet welding extending beyond abrupt changes in the direction of the welding must be indicated by additional arrows pointing to each section of the joint to be welded (fig. 3-29) except when the weld-all-around symbol is used.

3-19. DIMENSIONING OF INTERMITTENT FILLET WELDING

a. The pitch (center-to-center spacing) of intermittent fillet welding shall be shown as the distance between centers of increments on one side of the joint.

b. The pitch of intermittent fillet welding shall be shown to the right of the length dimension (A, fig 3-27).

c. Dimensions of chain intermittent fillet welding must be shown on both sides of the reference line. Chain intermittent fillet welds shall be opposite each other (fig. 3-30).

d. Dimensions of staggered intermittent fillet welding must be shown on both sides of the reference line as shown in figure 3-31.

Unless otherwise specified, staggered intermittent fillet welds on both sides shall be symmetrically spaced as in figure 3-32.

3-20. TERMINATION OF INTERMITTENT FILLET WELDING

a. When intermittent fillet welding is used by itself, the symbol indicates that increments are located at the ends of the dimensioned length.

b. When intermittent fillet welding is used between continuous fillet welding, the symbol indicates that spaces equal to the pitch minus the length of one increment shall be left at the ends of the dimensioned length.

c. Separate symbols must be used for intermittent and continuous fillet welding when the two are combined along one side of the joint (fig. 3-28).

3-21. SURFACE CONTOUR OF FILLET WELDS

a. Fillet welds that are to be welded approximately flat, convex, or concave faced without recourse to any method of finishing must be shown by adding the flush, convex, or concave contour symbol to the weld symbol, in accordance with the location specifications given in paragraph 3-7 (A, fig. 3-33).

b. Fillet welds that are to be made flat faced by mechanical means must be shown by adding both the flush contour symbol and the user's standard finish symbol to the weld symbol, in accordance with location specifications given in paragraph 3-7 (B, fig. 3-33).

c. Fillet welds that are to be mechanically finished to a convex contour shall be shown by adding both the convex contour symbol and the user's standard finish symbol to the weld symbol, in accordance with location specifications given in paragraph 3-7 (C, fig. 3-33).

d. Fillet welds that are to be mechanically finished to a concave contour must be shown by adding both the concave contour symbol and the user's standard finish symbol to the weld symbol in accordance with location specification given in paragraph 3-7.

e. In cases where the angle between fusion faces is such that the identification of the type of weld and the proper weld symbol is in question, the detail of the desired joint and weld configuration must be shown on the drawing.

NOTE

Finish symbols used here indicate the method of finishing (" c" = chiping, "G" = grinding, "H" = hammering, "M" = machining), not the degree of finish.

3-22. PLUG AND SLOT WELDING SYMBOLS

a. General. Neither the plug weld symbol nor the slot weld symbol may be used to designate fillet welds in holes.

b. Arrow Side and Other Side Indication of Plug and Slot Welds. Holes or slots in the arrow side member of a joint for plug or slot welding must be indicated by placing the weld symbol on the side of the reference line toward the reader (A, fig. 3-11). Holes or slots in the other side member of a joint shall be indicated by placing the weld symbol on the side of the reference line away from the reader (B, fig. 3-11).

c. Plug Weld Dimensions. Dimensions of plug welds must be shown on the same side of the reference line as the weld symbol. The size of a weld must be shown to the left of the weld symbol. Included angle of countersink of plug welds must be the user's standard unless otherwise indicated. Included angle of countersink, when not the user's standard, must be shown either above or below the weld symbol (A and C, fig. 3-34). The pitch (center-to-center spacing) of plug welds shall be shown to the right of the weld symbol.

d. Depth of Filling of Plug and Slot Welds. Depth of filling of plug and slot welds shall be completed unless otherwise indicated. When the depth of filling is less than complete, the depth of filling shall be shown in inches inside the weld symbol (B, fig. 3-34).

e. Surface Contour of Plug Welds and Slot Welds. Plug welds that are to be welded approximately flush without recourse to any method of finishing must be shown by adding the finish contour symbol to the weld symbol (fig. 3-35). Plug welds that are to be welded flush by mechanical means must be shown by adding both the flush contour symbol and the user's standard finish symbol to the weld symbol (fig. 3-36).

f. Slot Weld Dimensions. Dimensions of slot welds must be shown on the same side of the reference line as the weld symbol (fig. 3-37).

g. Details of Slot Welds. Length, width, spacing, included angle of countersink, orientation, and location of slot welds cannot be shown on the welding symbols. This data must be shown on the drawing or by a detail with a reference to it on the welding symbol, in accordance with location specifications given in paragraph 3-7 (D, fig. 3-33).

3-23. ARC SPOT AND ARC SEAM WELDS

a. General. The spot weld symbol, in accordance with its location in relation to the reference line, may or may not have arrow side or other side significance. Dimensions must be shown on the same side of the reference line as the symbol or on either side when the symbol is located astride the reference line and has no arrow side or other side significance. The process reference is indicated in the tail of the welding symbol. Then projection welding is to be used, the spot weld symbol shall be used with the projection welding process reference in the tail of the welding symbol. The spot weld symbol must be centered above or below the, reference line.

b. Size of Arc Spot and Arc Seam Welds.

(1) These welds may be dimensioned by either size or strength.

(2) The size of arc spot welds must be designated as the diameter of the weld. Arc seam weld size shall be designated as the width of the weld. Dimensions will be expressed in fractions or in decimals in hundredths of an inch and shall be shown, with or without inch marks, to the left of the weld symbol (A, fig. 3-38).

(3) The strength of arc spot welds must be designated as the minimum accept-able shear strength in pounds or newtons per spot. In arc seam welds, strength is designated in pounds per linear inch. Strength is shown to the left of the weld symbol (B, fig. 3-38).

c. Spacing of Arc Spot and Arc Seam Welds.

(1) The pitch (center-to-center spacing) of arc spot welds and, when indicated, the length of arc seam welds, must be shown to the right of the weld symbol (C, fig. 3-38).

(2) When spot welding or arc seam welding extends for the full distance between abrupt changes in the direction of welding, no length dimension need be shown on the welding symbol.

d. Extent and Number of Arc Spot Welds and Arc Seam Welds.

(1) When arc spot welding extends less than the distance between abrupt changes in the direction of welding or less than the full length of the joint, the extent must be dimensioned (fig. 3-39).

(2) When a definite number of arc spot welds is desired in a certain joint, the number must be shown in parentheses either above or below the weld symbol (fig. 3-40).

(3) A group of spot welds may be located on a drawing by intersecting center lines. The arrows point to at least one of the centerlines passing through each weld location.

e. Flush Arc Spot and Arc Seam Welded Joints. When the exposed surface of one member of an arc spot or arc seam welded joint is to be flush, that surface must be indicated by adding the flush contour symbol (fig. 3-41) in the same manner as that for fillet welds (para 3-21).

f. Details of Arc Seam Welds. Spacing, extent, orientation, and location of arc seam welds cannot be shown on the welding symbols. This data must be shown on the drawing.

3-24. GROOVE WELDS

a. General.

(1) Dimensions of groove welds must be shown on the same side of the reference line as the weld symbol (fig. 3-42).

(2) When no general note governing the dimensions of double groove welds appears, dimensions shall be shown as follows:

(a) When both welds have the same dimensions, one or both may be dimensioned (fig. 3-43).

(b) When the welds differ in dimensions, both shall be dimensioned (fig. 3-44).

(3) When a general note governing the dimensions of groove welds appears, the dimensions of double groove welds shall be indicated as follows:

(a) If the dimensions of both welds are as indicated in the note, neither symbol need be dimensioned.

(b) When the dimensions of one or both welds differ from the dimensions given in the general note, both welds shall be dimensioned (fig. 3-44).

b. Size of Groove Welds.

(1) The size of groove welds shall be shown to the left of the weld symbol (fig. 3-44).

(2) Specifications for groove welds with no specified root penetration are shown as follows:

(a) The size of single groove and symmetrical double groove welds which extend completely through the member or members being joined need not be shown on the welding symbol (A and B, fig. 3-45).

(b) The size of groove welds which extend only partly through the member members being joined must be shown on the welding symbol (A and B, fig. 3-46).

(3) The groove welds, size of groove welds with specified root penetration, except square must be indicated by showing the depth of chamfering and the root penetration separated by a plus mark and placed to the left of the weld symbol. The depth of chamfering and the root penetration must read in that order from left to right along the reference line (A and B, fig. 3-47). The size of square groove welds must be indicated by showing only the root penetration.

(4) The size of flare groove welds is considered to extend only to the tangent points as indicated by dimension lines (fig. 3-48).

c. Groove Dimensions

(1) Root opening, groove angle, groove radii, and root faces of the U and J groove welds are the user's standard unless otherwise indicated.

(2) When the user's standard is not used, the weld symbols are as follows:

(a) Root opening is shown inside the weld symbol (fig. 3-49).

(b) Groove angle of groove welds is shown outside the weld symbol (fig. 3-42).

(c) Groove radii and root faces of U and J groove welds are shown by a cross section, detail, or other data, with a reference to it on the welding symbol, in accordance with location specifications given in paragraph 3-7 (fig. 3-22).

d. Back and Backing Welds. Bead-type back and backing welds of single-groove welds shall be shown by means of the back or backing weld symbol (fig. 3-50).

e. Surface Contour of Groove Welds. The contour symbols for groove welds (F, fig. 3-51) are indicated in the same manner as that for fillet welds (para 3-21).

(1) Groove welds that are to be welded approximately flush without recourse to any method of finishing shall be shown by adding the flush contour symbol to the weld symbol, in accordance with the location specifications given in paragraph 3-7 (fig. 3-52).

(2) Groove welds that are to be made flush by mechanical means shall be shown by adding the flush contour symbol and the user's standard finish symbol to the weld symbol, in accordance with the location specifications given in paragraph 3-7 (fig. 3-53).

(3) Groove welds that are to be mechanically finished to a convex contour shall be shown by adding both the convex contour symbol and the user's standard finish symbol to the weld symbol, in accordance with the location specifications given in para 3-7 (fig. 3-54).

3-25. BACK OR BACKING WELDS

a. General.

(1) The back or backing weld symbol (fig. 3-50) must be used to indicate bead-type back or backing welds of single-groove welds.

(2) Back or backing welds of single-groove welds must be shown by placing a back or backing weld symbol on the side of the reference line opposite the groove weld symbol (fig. 3-50).

(3) Dimensions of back or backing welds should not be shown on the welding symbol. If it is desired to specify these dimensions, they must be shown on the drawing.

b. Surface Contour of Back or Backing Welds. The contour symbols (fig. 3-55) for back or backing welds are indicated in the same manner as that for fillet welds (para 3-21).

3-26. MELT-THRU WELDS

a. General.

(1) The melt-thru symbol shall be used where at least 100 percent joint penetration of the weld through the material is required in welds made from one side only (fig. 3-56).

(2) Melt-thru welds shall be shown by placing the melt-thru weld symbol on the side of the reference line opposite the groove weld, flange, tee, or corner weld symbol (fig. 3-56).

(3) Dimensions of melt-thru welds should rot be shown on the welding symbol. If it is desired to specify these dimensions, they must be shown on the drawing.

b. Surface Contour of Melt-thru Welds. The contour symbols for melt-thru welds are indicated in the same manner as that for fillet welds (fig. 3-57).

3-27. SURFACING WELDS

a. General.

(1) The surfacing weld symbol shall be used to indicate surfaces built up by welding (fig. 3-58), whether built up by single-or multiple-pass surfacing welds.

(2) The surfacing weld symbol does not indicate the welding of a joint and thus has no arrow or other side significance. This symbol shall be drawn on the side of the reference line toward the reader and the arrow shall point clearly to the surface on which the weld is to be deposited.

b. Size of Built-up Surfaces. The size (height) of a surface built up by welding shall be indicated by showing the minimum height of the weld deposit to the left of the weld symbol. The dimensions shall always be on the same side of the reference line as the weld symbol (fig. 3-58). When no specific height of weld deposit is desired, no size dimension need be shown on the welding symbol.

c. Extent, Location, and Orientation of Surfaces Built up by Welding. When the entire area of a plane or curved surface is to be built up by welding, no dimension, other than size, need be shown on the welding symbol. If only a portion of the area of a plane or curved surface is to be built up by welding, the extent, location, and orientation of the area to be built up shall be indicated on the drawing.

3-28. FLANGE WELDS

a. General.

(1) The following welding symbols are used for light gage metal joints involving the flaring or flanging of the edges to be joined (fig. 3-59). These symbols have no arrow or other side significance.

(2) Edge flange welds shall be shown by the edge flange weld symbol (A, fig. 3-59).

(3) Corner flange welds shall be shown by the corner flange weld symbol (B, fig. 3-59). In cases where the corner flange joint is not detailed, a break in the arrow is required to show which member is flanged (fig. 3-59).

b. Dimensions of Flange Welds.

(1) Dimensions of flange welds are shown on the same side of the reference line as the weld symbol.

(2) The radius and the height above the point of tangency must be indicated by showing the radius and height, separated by a plus mark, and placed to the left of the weld symbol. The radius and height must read in that order from left to right along the reference line (C, fig. 3-59).

(3) The size (thickness) of flange welds must be shown by a dimension placed outward of the flange dimensions (C, fig. 3-59).

(4) Root opening of flange welds are not shown on the welding symbol. If specification of this dimension is desired, it must be shown on the drawing.

c. Multiple-Joint Flange Welds. For flange welds in which one or more pieces are inserted between the two outer pieces, the same symbol shall be used as for the two outer pieces, regardless of the number of pieces inserted.

3-29. RESISTANCE SPOT WELDS

a. General. Resistance spot weld symbols (fig. 3-3) have no arrow or other side significance in themselves, although supplementary symbols used in con-junction with them may have such significance. Resistance spot weld symbols shall be centered on the reference line. Dimensions may be shown on either side of the reference line.

b. Size of Resistance Spot Welds. Resistance spot welds are dimensioned by either size or strength as follows:

(1) The size of resistance spot welds is designated as the diameter of the weld expressed in fractions or in decimals in hundredths of an inch and must be shown, with or without inch marks, to the left of the weld symbol (>fig. 3-60).

(2) The strength of resistance spot welds is designated as the minimum acceptable shear strength in pounds per spot and must be shown to the left of the weld symbol (fig. 3-61).

c. Spacing of Resistance Spot Welds.

(1) The pitch of resistance spot welds shall be shown to the right of the weld symbol (fig. 3-62).

(2) When the symbols are shown directly on the drawing, the spacing is shown by using dimension lines.

(3) When resistance spot welding extends less than the distance between abrupt changes in the direction of the welding or less than the full length of the joint, the extent must be dimensioned (fig. 3-63).

d. Number of Resistance Spot Welds. When a definite number of welds is desired in a certain joint, the number must be shown in parentheses either above or below the weld symbol (fig. 3-64).

e. Flush Resistance Spot Welding Joints. When the exposed surface of one member of a resistance spot welded joint is to be flush, that surface shall be indicated by adding the flush contour symbol (fig. 3-3) to the weld symbol, (fig. 3-65) in accordance with location specifications given in paragraph 3-7.

3-30. RESISTANCE SEAM WELDS

a. General.

(1) Resistance seam weld symbols have no arrow or other side significance in themselves, although supplementary symbols used in injunction with them may have such significance. Resistance seam weld symbols must be centered on the reference line.

(2) Dimensions of resistance seam welds may be shown on either side of the reference line.

b. Size of Resistance Seam Welds. Resistance seam welds must be dimensioned by either size or strength as follows:

(1) The size of resistance seam welds must be designated as the width of the weld expressed in fractions or in decimals in hundredths of an inch and shall be shown, with or without inch marks, to the left of the weld symbol (fig. 3-66).

(2) The strength of resistance seam welds must be designated as the minimum acceptable shear strength in pounds per linear inch and must be shown to the left of the weld symbol (fig. 3-67).

c. Length of Resistance Seam Welds.

(1) The length of a resistance seam weld, when indicated on the welding symbol, must be shown to the right of the welding symbol (fig. 3-68).

(2) When resistance seam welding extends for the full distance between abrupt changes in the direction of the welding, no length dimension need be shown on the welding symbol.

(3) When resistance seam welding extends less than the distance between abrupt changes in the direction of the welding or less than the full length of the joint, the extent must be dimensioned (fig. 3-69).

d. Pitch of Resistance Seam Welds. The pitch of intermittent resistance seam welding shall be designated as the distance between centers of the weld increments and must be shown to the right of the length dimension (fig. 3-70).

e. Termination of Intermittent Resistance Seam Welding. When intermittent resistance seam welding is used by itself, the symbol indicates that increments are located at the ends of the dimensioned length. When used between continuous resistance seam welding, the symbol indicates that spaces equal to the pitch minus the length of one increment are left at the ends of the dimensional length. Separate symbols must be used for intermittent and continuous resistance seam welding when the two are combined.

f. Flush Projection Welded Joints. When the exposed surface of one member of a projection welded joint is to be made flush, that surface shall be indicated by adding the flush contour symbol (fig. 3-3) to the weld symbol, observing the usual location significance (fig. 3-79).

3-31. PROJECTION WELDS

a. General.

(1) When using projection welding, the spot weld symbol must be used with the projection welding process reference in the tail of the welding symbol. The spot weld symbol must be centered on the reference line.

(2) Embossments on the arrow side member of a joint for projection welding shall be indicated by placing the weld symbol on the side of the reference line toward the reader (fig. 3-72).

(3) Embossment on the other side member of a joint for projection welding shall be indicated by placing the weld symbol on the -side of the reference line away from the reader (fig. 3-73).

(4) Proportions of projections must be shown by a detail or other suitable means.

(5) Dimensions of projection welds must be shown on the same side of the reference line as the weld symbol.

b. Size of Projection Welds.

(1) Projection welds must be dimensioned by strength. Circular projection welds may be dimensioned by size.

(2) The size of circular projection welds shall be designated as the diameter of the weld expressed in fractions or in decimals in hundredths of an inch and shall be shown, with or without inch marks, to the left of the weld symbol (fig. 3-74).

(3) The strength of projection welds shall be designated as the minimum acceptable shear strength in pounds per weld and shall be shown to the left of the weld symbol (fig. 3-75).

c. Spacing of Projection Welds. The pitch of projection welds shall be shown to the right of the weld symbol (fig. 3-76).

d. Number of Projection Welds. When a definite number of projection welds is desired in a certain joint, the number shall be shown in parentheses (F, fig. 3-77).

e. Extent of Projection Welding. When the projection welding extends less than the distance between abrupt changes in the direction of the welding or less than the full length of the joint, the extent shall be dimensioned (fig. 3-78).

f. Flush Resistance Seam Welded Joints. When the exposed surface of one member of a resistance seam welded joint is to be flush, that surface shall be indicated by adding the flush contour symbol (fig. 3-3) to the weld symbol, observing the usual location significance (fig. 3-71).

3-32. FLASH OR UPSET WELDS

a. General. Flash or upset weld symbols have no arrow side or other side significance in themselves, although supplementary symbols used in conjunction with then may have such significance. The weld symbols for flash or upset welding must be centered on the reference line. Dimensions need not be shown on the welding symbol.

b. Surface Contour of Flash or Upset Welds. The contour symbols (fig. 3-3) for flash or upset welds (fig. 3-80) are indicated in the same manner as that for fillet welds (paragraph 3-21).

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