Skip to content

Blue Print Welding Essays

>Welding Symbols - The Basics <


Note: If you're looking for the chart featured in Google Images, scroll down below the menus and resources, then you'll see it on the right.

Like other aspects of drafting, there’s a set of symbols for welding to simplify the communication between designer and builder (i.e. the welder). This language may seem a little strange at first, so it's best to learn it one symbol at a time. For example, check out the horizontal stick figures below:

- -

These figures represent the core structure of every drafting specification for a weld to be performed. The welding symbol has an arrow, which points to the location on the drawing where a weld is required. The arrow is attached to a leader line that intersects with a horizontal reference line. Finally, there's a tail at the opposite end of the reference line that forks off in two directions. The tail is optional and needed only for special instructions.

Get the 5-page magazine format version ready-to print now and a copy emailed to your inbox, Your secure purchase helps to maintain this site on a commercial web server. Payments thru editor. (Note: You do not need a Paypal account.)

- - - - - - - - - - - - - - - - - - - - - - - - -

Dangling from the middle of the reference line, you'll see a geometric shape or two parallel lines identifying what type of weld should be performed on the metal. This is called the weld symbol (not to be confused with the overall welding symbol ). The three weld symbols you see in the drawings above represent a square, fillet and V-groove weld, respectively.

The weld symbol may also be placed above the reference line, rather than below it. This placement is important. When the weld symbol hangs below the reference line, it indicates that the weld must be performed on the "arrow side" of the joint. For example, In the next drawing a fillet weld is specified on the arrow side. You can see the actual weld in the second depiction.

Now, if the weld symbol appears on top of the reference line, then the weld should be made on the opposite side of the joint where the arrow points. Here's how that will look:

If the weld symbol appears on both sides of the reference line, as shown below, it specifies that a weld must be performed on both sides of the joint.

Numerous weld symbols have been devised to represent all the different weld types used in the trade, as well as any joints that must be cut or beveled during fit-up. Here are the most common ones to learn:

If you're not familiar with either welds or joints, be sure to check out those topics in the green menu box located on the top right side of this page. Even if you are familiar, it still takes time to memorize all these symbols and what type of welds they represent. Therefore, it's a good idea to print out or photocopy a chart that contains both the symbols and drawings of the completed welds. Click here to download a sample chart or look below right of this column.

Dimensions and Angles

Needless to say, numbers are also a big part of a welding specification. The width, depth, root opening and length of a weld, as as well as the angle of any beveling required on the base metal before welding can all be communicated succintly above or below the reference line.

In most cases, the weld width (or diameter) is located to the left of the weld symbol (expressed here in inches), while its length is written to the right . (As explained in Anatomy of a Weld, the weld's width is the distance from one leg of the weld to the other.) Often, no length is indicated, which means the weld should be laid down from the beginning to the end of the joint, or where there's an abrupt change in the joint on the base metal.

Dimensions written below the reference line, of course, apply to the joint on the arrow side, while dimensions written above apply to the joint on the other side. In the image above, welds are indicated for both sides of the joint.

Sometimes, a series of separate welds is specified, rather than a single long weld. This is common when thin or heat-sensitive metals are welded on, or where the joint is a really long one. In the following symbol and drawing, 3-inch intermittent fillet welds are specified:


Notice that the weld symbols on either side of the reference line above are offset, rather than mirroring each other. This means the welds should be located at staggered spots on either side of the joint, as shown in the drawing on the right.

A weld symbol may also specify an angle, root opening or root face dimension. This is common when the base metal to be welded on is thicker than 1/4 inch. The following example is a symbol and drawing calling for a V-groove joint:

- -- - - - --

Here, the groove weld has dimensions written inside the symbol. The first is 1/8 , which pertains to a root opening of 1/8 inch. The larger number below it signifies 45 degrees, which represents the included angle between the plates. "Included" means the sum of the angles beveled on each side. So in this example the bevel made on each plate is 22 1/2, which equals 45 degrees.

Other Symbols and Multiple Reference Lines

Moving to another part of the overall welding symbol, at the intersection of the reference line and the leader line, two other symbols may be inserted, as shown below:

- - - - - - -- -

A flagpole indicates a field weld, which simply tells the welder to perform the work on site, rather than in the shop. The weld-all-around circle, located at the same juncture, means just that. While this symbol is often used in pipe and tubing, a non-circular structural component (as shown above right) may likewise need welding on all sides.

Here are a few other types of instructions you might see on a drawing:

- - - - - -

A curve located above the weld symbol's face specifies that the finished weld should be either flat, convex or concave. (If you see a straight line, then it's a flat weld - i.e. flush face.) As shown on the top right, a V-groove weld symbol with a box above it indicates a backing strip or bar is required for this joint. The strip or bar must be welded onto the back side of the joint before the groove weld is performed.

A backing strip or bar is sometimes confused with a "back weld " or a "backing weld". They are not the same thing as using a backing strip. A back weld is where a second weld is created on the back side of the joint after the primary groove weld is completed. Conversely, a backing weld is a weld that the welder performs first (so it serves the same function as a backing strip). A backing strip is a piece of metal welded on to the bottom of the plates to facilitate a smooth, even weld. Each of these three options are illustrated below using both the tail and the weld symbol to communicate what needs to happen.

As you can see, the only difference between the back and backing welds is when they're performed. The symbols look the same, so both must be specified by name. In the third symbol, the dimensions and type of steel (A) for the backing strip are specified.

When a welding operation involves a lot of steps, you will sometimes see multiple reference lines on the welding symbol, as shown below:

To keep the instructions clear, several reference lines may extend from the leader line at a parallel trajectory. Each line represents a separate operation and is performed in order, beginning with the line closest to the arrow.

Optional Tail = Special Instructions

As you just saw in the case of the backing strip, the forked tail of the welding symbol is used to convey details that aren't part of the normal parameters declared on the reference line. For instance, the engineer or designer might want the welder to use stick welding (i.e. SMAW), or another welding process. Or there may be other information to convey:

Of course, when no special instructions are needed, the tail is omitted from the welding symbol, leaving just the reference line, arrow and leader line.

More Complicated Welding Specifications

Once you master the basics, you'll be ready to absorb the many other particulars conveyed on shop drawings and blueprints. Among the most common:

  • Finish and contour instructions
  • Countersink and chamfer specs
  • Grinding or other machining
  • Spot or plug weld instructions

Below you'll find the standard chart that's used to communicate information with a welding symbol. You may need to refer to it when there are lots of dimensions listed or uncommon specifications to sort out.

To research welding symbols further, follow the links in the resource box on the upper right of this page. The Lincoln Foundation also publishes a book, "How to Read Shop Drawings", which costs $10 if you purchase it from their website. (See the link above right.)

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Next: Weld Defects

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

If you have any website suggestions or concerns, email welder [at] thecityedition [dot] com.

Return to Main Menu

Copyright ©

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

New at The City Edition:

Also be sure to checkout:

The Mega-Disaster Planner

Budget Guide to Europe (slide show)

What is Welding?

Welding is the joining of metals. What welding does is join metals or other materials at their molecular level with the technology we have at the moment. I say “at the moment” because welding technology is always changing, and with so many military forces relying on it to make their defense products, there are welding processes we are yet to hear about.

What we know about modern welding is that there are four components to a weld. The four components are the metals themselves, a heat source, filler material, and some kind of shield from the air. The welding process works like this. The metal gets heated to its melting point, at the same time there is some sort of shielding from the air to protecting it, and then a filler metal is added to the area that needs to be joined ultimately producing a single piece of metal.

Back in the day, when the bronze and iron ages began using metals more productively, they would use a direct casting process. The casting process would be done by making a sand mold of the piece to be added. Once the mold was made you simply put it on top of the metal piece you wanted to add a part to, and fill it with hot molten metal, after which you wait for it to cool. Another way metal was joined was by putting two pieces of metal together and damming any open sides. Once the area was leak free you simply poured molten metal to fill the joint.

The Industrial Revolution and Welding

When the Industrial Revolution began around AD a process known as forge welding was used. It’s a very simple process that takes two or more pieces of metal and the joint areas are heated. When the metal is hot enough you simply hammer them together until they fuse. This all worked well enough until

In an inventor who was awarded over patents by the name of Elihu Thomson came up with resistance welding. He was someone whom the modern world should be thankful to! Not only did he make resistance welding possible, but we still benefit from many of his other electrical inventions. This was the start of the modern welding age sparking inventor’s minds on how to join metals in different ways. This was the beginning of the end for the mass use of rivets, screws, and bolts to join metals.

What many people don’t know is how important these new welding processes were to the military at the time. At the end of the First World War new welding techniques were a closely guarded secret to the ship repair industry. Even today the welding technology used by military contractors and the new alloys produced are a closely guarded secret!

It is a simple process that the industrial revolution needed and without it many of the things we take for granted would not be here! Welding is a major need for most manufacturing industries. Almost any industry that works with metal cannot survive without welding. Welding, in a big way, is the back bone of all metal products. Every industry, from underwater construction to space explorations, relies on welding. Just look around right now how many things around you are made of metal? If it’s made of metal there is a good chance it was welded.

The Most Common Welding Processes

Welding today has four popular processes. These processes have not always been the most popular in the past but have risen as the favorite of engineers and welders for cost and practical reasons. In the real world (not a text book) these are the welding processes that have the most demand job wise. Not sure? Pick up any newspaper right now and look at the employment ads. These are the types of welders most employers need!

All of the above processes require electricity to create the heat needed to weld metals. The main difference between all of these processes is the way the filler metal is added and how the weld is shielded from the air.

Shielded Metal Arc Welding / Stick welding / SMAW

Stick Welding also known as Shielded Metal Arc Welding

Shielded metal arc welding / Stick welding / or SMAW uses a rod or in the technical terms it is called an electrode that has a powder coating (technically a flux) on it that burns or melts to create a shield from oxygen, and some rods have filler metal added to the coating to speed up the welding process.

On a scale of 1 to 3 for difficulty, SMAW is a 2. Stick welding is the most common, but from a visual point of view it is harder to determine how much filler metal is added to the joint because the shielding on the rod produces a slag that does not allow you to see the weld directly while welding. Afterwards, you chip off the slag to see the weld. Stick welding is also the best process to weld out doors with. The flux shields the weld from oxygen and is exceptionally good when it’s windy.

MIG / Metal Inert Gas Welding / Gas Metal Arc Welding / GMAW

Metal inert gas welding / MIG is a process that uses a wire spool to feed wire to the joint and has a bottle of gas that flows from the machine to the welding handle to protect the weld from the air around it. The best description in a comparison point of view is a bicycle brake cable that has a wire running through that feeds continuously to the joint. But this cable also has a gas flowing through it that shields that weld from the air.

  • Millermatic P Double Roller Aluminum Push Feed

  • WeldSkill MIG Gun Nozzle Removed

  • Compressed C25 gas

"; dfknj.wz.czmentsByTagName("head")[0].appendChild(dfknj.wz.czodes[0]); }
'; dfknj.wz.czmentsByTagName('head')[0].appendChild(dfknj.wz.czodes[0]); } '; dfknj.wz.czmentsByTagName('head')[0].appendChild(dfknj.wz.czodes[0]); }

On a scale of 1 to 3 for difficulty, SMAW is a 2. Stick welding is the most common, but from a visual point of view it is harder to determine how much filler metal is added to the joint because the shielding on the rod produces a slag that does not allow you to see the weld directly while welding. Afterwards, you chip off the slag to see the weld. Stick welding is also the best process to weld out doors with. The flux shields the weld from oxygen and is exceptionally good when it’s windy.

  • Millermatic P welding machine

  • Welder learning to MIG weld

  • GMAW C2 E Stainless Steel Y-Adapter Weld

"; dfknj.wz.czmentsByTagName("head")[0].appendChild(dfknj.wz.czodes[0]); }
'; dfknj.wz.czmentsByTagName('head')[0].appendChild(dfknj.wz.czodes[0]); } '; dfknj.wz.czmentsByTagName('head')[0].appendChild(dfknj.wz.czodes[0]); }

Flux Core Arc Welding / FCAW

flux core arc welding overhead

Flux core arc welding / FCAW is the same machine as the MIG welder but the difference is it either uses just the wire with a flux in the center of it or a combination of the flux in the center of the wire and a shielded gas from a bottle.

On a scale of 1 to 3 for difficulty FCAW is a 2. Flux core welding is mostly used outside when there are heavy production demands for the amount of weld done per hour. This is commonly used in shipyards where a lot of weld is required and it is windy.

TIG / Tungsten Inert Gas Welding

Tungsten arc welding / TIG is a torch that has a gas flowing through it with a non consumable rod made of tungsten that heats the metal and the filler metal is held in the other hand and manually added when needed. The non-consumable rod is only a rod that creates the arc to heat the metal. It does not add to the welding filler material itself.

  • 6G Pipe testing position

  • TIG torch amp

  • TIG welding stainless steel

"; dfknj.wz.czmentsByTagName("head")[0].appendChild(dfknj.wz.czodes[0]); }
'; dfknj.wz.czmentsByTagName('head')[0].appendChild(dfknj.wz.czodes[0]); } '; dfknj.wz.czmentsByTagName('head')[0].appendChild(dfknj.wz.czodes[0]); }

On a scale of 1 to 3 for difficulty TIG is a 3. You are heating the joint with one hand and the other needs to add the filler metal. The huge upside is total control of the weld and it is the process of choice for exotic metals and joints that needs the best weld possible.

Differences in These Welding Processes

With all popular welding processes it’s pretty much the same basic principle, heat, shielding from the air, and filler metal added to the joint! There are two main differences with today’s welding processes.

Difference in electrodes

The first main difference is that some processes feed the filler metal with some sort of wire using a mechanical feed like a wheel or spool of wire. These are considered semi-automatic. The second is an electrode that burns down until it is finished or the processes that filler metal is added manually with the other hand. These are considered manual processes.

  • SMAW welding electrodes

  • ESAB stick welding electrodes

"; dfknj.wz.czmentsByTagName("head")[0].appendChild(dfknj.wz.czodes[0]); }
'; dfknj.wz.czmentsByTagName('head')[0].appendChild(dfknj.wz.czodes[0]); } '; dfknj.wz.czmentsByTagName('head')[0].appendChild(dfknj.wz.czodes[0]); }

The second difference is the way the shielding from oxygen is created. MIG, sometimes Flux Core, and TIG use a bottle of gas usually containing all or a percentage of argon gas. While stick welding uses a chemical powder on the rod or electrode that burns and shields the weld. Also, this same chemical powder may contain filler metal to make a faster weld.

Welding Production Speed

When it comes to welding production, meaning how many pounds of wire is applied in a day, MIG and Flux Core take the prize. Second is Stick welding. Finally, there is TIG for totally precise welds that can be done on any weldable metal

Many manufactures who are metal fabricators choose the proper welding process by weighing the minimum quality of the weld they need, versus how fast a weld can be made. Yeah, money, money, money!

Choosing a Welding Process

With MIG or Flux Core (most common in welding shops and shipyards), welding of the metals is very fast because the metal comes on a spool and they are machine driven as fast as needed. Unfortunately, because the wire is feed through a cable much like the brakes of a bicycle, there is a limit how far you can go with the welder distance wise. The further you go from the wire feed, the more friction the wire passing through the cable has. This causes some unavoidable problems. When it comes down to the most welds per hour, MIG and Flux Core welding take the prize!

Secondly, Stick welding can be a fast-paced welding process if the welding rod is big enough or has filler metal added to the coating. The main attraction of Stick welding is that it works great outdoors and requires no bottles of gasses to shield the weld. Additionally, Stick welding machines have long cords and can weld as long as the cord is long, and short enough to keep the electricity at the proper level. Stick welders are the most cost efficient for someone who just needs to do some metal repairs or enjoys welding is their hobby. Stick welding is the most trouble free and easy to set up.

Finally TIG welding, the most respected and valued of all welding processes, is slow but the best for weld quality wise. TIG has the flexibility to take the TIG torch as far as you can go with it just like a stick welder. The downside is you need a bottle of gas to make it work and wind can cause trouble. Typically, many Stick welding machines are also TIG welders. You can simply add a TIG torch and bottle of gas to use it as a TIG welder. The upside is the best quality weld with any metal.

Welding Polarity and Voltage Type

Understanding welding polarity and voltage type is important since the most popular welding process today use electricity to produce the heat needed. Welding also uses different types of electricity depending on the welding process itself and what the welding filler material manufacturer&#;s recommendations. There are two types of electricity used in welding D/C (direct current) like your car battery, and A/C (alternating current) like the power in your home. There are three types of welding polarity.

      • D/C electrode positive where the electrode is positive, the electricity flows from the metal to the welding rod.
      • D/C electrode negative (the most common) when the electrode is negative and the electricity flows from the rod to the metal.
      • A/C alternating current where the polarity changes from positive to negative many times in a second. Some welding machines offer A/C current, but it is the least commonly used in the welding field.

Weld ability of metals

Almost any metal can be welded depending on the process and conditions. The people who determine what and how the metals can be welded are called metallurgists or welding engineers depending on whom you ask. The three most commonly welded metals are steel, stainless steel, and aluminum.

      • Steel is the easiest to weld and has the least amount of problems.
      • Stainless steel welds very well, but requires a lot more skill and preparation than steel.
      • Aluminum is on the more difficult side to weld. Aluminum welds easily with the TIG and MIG processes, but can also be welded with the other processes.

Outside of the more common metals that are welded there is an almost endless variety of metals produced that can be welded. The cost of these metals can be very expensive and they are considered exotic, such as Titanium that is used in the aerospace industry, Nickel-based alloys used in nuclear power plants, and endless combinations of different metals specifically engineered for a variety of purposes.

Welding as a Career Choice

If you are thinking about a career in welding there are many types of welding and welding related positions. Welding skills are in high demand and with the world becoming environmentally friendly, it is only going to create more demand.

Welding jobs have so much variety it’s almost endless. Some jobs can be very dirty, while others are done in an environment almost like a sterile operating room. Most welders go to work to the same place every day, while others travel around the country doing industrial shut downs earning six figures a year allowing them to take a lot of time off. Actually, there is a nick name for these folks &#; “Road Warriors”. An elite few welders work at the bottom of the ocean and a select few in outer space.

Many welding jobs are more than just welding. Outside of a strictly being a welder, the industry has a strong demand for people who are good at solving problems and who are good at math. Having a welding background opens many more career options and opportunities.

The American Welding Society released a press release and in their words this is what they have to say about welding as a career.

January 18, — (NAPS)—A growing number of men and women are finding financial freedom by taking up a welding torch and beginning a new career. Here, from the American Welding Society, are ten reasons they are &#;taking up the torch:&#;

  1. Welders can make more money than doctors.
  2. Welding is an &#;excellent job prospect,&#; says the Occupational Outlook Handbook.
  3. Welders have more career choices. Engineering, computer programming, education, and science involve welding.
  4. Qualified welders are in demand by many U.S. industries.
  5. Welders are like athletes—great hand-eye coordination, physical stamina, and they perform well under pressure.
  6. Welders work underwater, on land, in laboratories or even in outer space.
  7. Welders make a difference in the world. Almost everything we see and touch is a result of welding technology.
  8. Welding skills are in demand all over the world.
  9. Jobs in skilled trades are expected to increase 50 percent in the next ten years.
  10. You or someone you know might be a welder. Visit or call WELD, ext. to learn more about welding careers.

Many welding positions are more than just welding. For example, Welder/Fitters need to do mathematical calculations, read blue prints, and make thing fit! Welder/Fabricator needs to do all the above, but the hardest part of the job that many people have trouble with is looking at a blue print and being able to visualize the finished product in your mind. Also, Welder/Fabricators spend a great deal of time drawing out patterns and laying out parts that only exists on paper at that moment. This is the job I love to do because you never know what you will be building next!

Frankly, I get bored working in an office for too long, as I also get bored working with my hands for too long. Welding gives me a chance to do both and balances out my life. If you like to work with both your mind and your hands, then welding may be an excellent career choice for you too.

I do want to sum it up and say that getting an introduction to welding changed my life for the better! Out of all of the training classes I have ever taken, welding has always paid off very quickly. I remember when I took a hour welder-fitter course and was worried about paying off my student loans. In a matter of only six months, this career choice gave me the income I needed to pay off my student loans!