The Art of Sculpture Welding: From Concept to Creation

PART I

Beginning Gas Metal Arc Welding Projects

Gas Metal Arc Welding

(GMAW), sometimes referred to as MIG (Metal Inert Gas) welding, was invented over a century ago, but it took until the late 1950s and early 1960s before the process was affordable and versatile enough to be extensively used. Today, MIG welding is the most common method of welding, especially in industry.

Many people think that MIG welding is as simple as picking up the gun and pushing the trigger. This is a huge misconception. As with other welding processes, a person needs to know how to set the welder for proper penetration, which way to aim the gun, how to move and advance down the weld joint, and how to identify and maintain the proper arc distance, as well as how to care for and clean the machine and its many parts.

This section provides the beginner welder an opportunity to build something fun and learn the MIG welding process. Both projects provide the same learning experiences and can be very beneficial in understanding the basic fabrication processes.

CHAPTER 1

Truck

While assembling the truck, you will learn and develop a variety of proficiencies in the welding shop environment. These include a working knowledge of welding equipment, power tools, hand tools, layout tools, and machinery. You will become familiar with identifying steel, using a plasma cutter and its accessories, and how to properly assemble a basic welding project. The project will supply plenty of practice using a MIG welder to tack parts and weld the basic joints.

Specifically, this project focuses on proper layout of parts, proper cleanup after cutting, and the importance of tacking parts together prior to welding joints solid. At times, the truck may seem tedious to build due to the large amount of parts, but is rewarding when complete.

STEP 1. Identify the steel needed for truck fabrication.

Before building any project, a person must be able to identify different types of pre-fabricated steel shapes. Without properly knowing how to identify steel, costly and time consuming mistakes can be made.

There are a variety of shapes, most of which can be identified by thickness, width, height, or diameter. Some of the more common and familiar shapes include; square tube, flat bar (strap), round bar (rod), angle iron, rectangular tube, pipe, square bar, and expanded metal (Figure 1-1). Other commonly used products are sheet metals, channel iron, and W-beams.

Figure 1-1. a. Square tube is identified by height, width, and thickness. Example: 1’ × 1’ × 10ga sq tube.

b. Flat bar, also known as strap, is identified by thickness and width. Example: 1/4 × 1 strap.

c. Round bar, also referred to as rod, is identified by its diameter. Example: 1/4" rod.

d. Angle iron is identified by height, width, and thickness. Example: 1 × 1 × 3/16" angle.

e. Rectangular tube is identified by height, width, and thickness. Example 1 × 2 × 14ga rectangular tube.

f. Pipe is identified by inside and outside diameters as well as wall thickness.

g. Square bar is identified by its height and width. Example: 1/4 × 1/4 square bar.

h. Expanded metal is a sheet product that comes in a variety of sizes. It is identified by its web distance, metal thickness, and the sheet size. Example: 4’ × 8’- 3/4" × 9ga Expanded or Expanded Flush. Expanded metal has raised webs whereas expanded Hush has a smooth surface.

When building a project it is helpful to refer to a parts list (Figure l-2a). It can help you deter-mine your total steel requirements, including types of steel you will need. It will also allow you to easily find individual lengths and widths of different parts.

Before beginning a project, it is also helpful to review the plan views. These views help to identify how parts fit together as a whole (Figure l-2b).

Figure l-2a. Parts List.

Figure 1-2b Front, back, top, bottom, and side orthographic views of the truck with total height, width, and depth dimensions.

When ordering pipe, you should refer to a pipe reference chart to be sure of what you are getting. For example, 2 schedule 40 pipe has a 2.375 outside diameter and 2.06 inside diameter with a wall thickness of .154. 3/8 schedule 40 pipe has a .675 outside diameter and .091 inside di-ameter with a wall thickness of .091. The size of pipe doesn’t match the diameter of pipe until it reaches 6" or larger.

HELPFUL HINT

Figure 1-3. Parts layout guide.

STEP 2. Collect the needed steel.

After reviewing the parts list and plan views, make a list of the types of steel needed to build the project. List the amount of feet or square feet needed and order the steel that isn’t currently available in your shop.

STEP 3. Lay out your sheet metal parts.

Before you begin locating and marking lines, consider the following points.

First, when laying out parts, you should make use of the sheet metal as efficiently as possible. The suggested layout plan in Figure 1-3 utilizes the sheet of steel with minimal waste. Notice that there is 1/8 gap between each part. By laying out parts in this manner, you limit the number of required cuts because when you cut a side of one part, you are also cutting a side of another. Most plasma kerf widths are approximately 1/16 or slightly larger. If you cut down the center of the 1/8 gap, there will be 1/32 for final clean up on both edges. This can be helpful if you are a beginner at using the plasma torch with a straight edge guide. If the torch is not slid along the straight edge smoothly, your line can be jagged. If the torch is not held perpendicular to the surface of the sheet metal, the kerf will be beveled. Having a little room for error in cutting will minimize the likelihood of having to re-cut later.

Second, choose the most accurate method possible for marking your lines. Common marking tools consist of scribes (Fig. 1-4), soapstone pencils (Fig. 1-5), and permanent markers. Due to the line width of markers and soapstone, sometimes as thick as 1/8" or more, I recommend using a scribe that produces a very thin accurate line (Fig. 1-6). Because a scribed line is so thin, it can be difficult to see. It may be helpful to use a marker to place a guide line just inside of your scribed line so that it is easier to locate later when lining up your straight edge for plasma cutting, as in Fig. 1-7.

Figure 1-4. A scribe is a pointed instrument used to mark or score a line that is used as a guide for cutting. Holding the scribe at a slight angle allows you to scratch the surface of the metal right next to your straight edge guide.

Figure 1-5. Soapstone pencil.

Figure 1-6. Lines drawn with a scribe.

Figure 1-7. A line drawn with a marker can be helpful in locating scribed lines more easily.

Last, when measuring and marking your cut paths, you should have both a tape measure that has been checked for accuracy and a good quality combination square. Measuring accurately cannot be overlooked when fabricating.

Now, using the most accurate tools available, lay out your parts as the layout guide suggests in Figure 1-3. (See Figures 1-8, 1-9, and 1-10 for part dimensions.)

You may find it easiest to first cut a piece of steel 2’-8 × l’-2 prior to laying out your parts. That way, if you don’t complete your part layout in the time period you’ve set aside, the metal sheet can easily be laid aside for completion on another day. Make sure to keep the steel square when cutting; this will save time when laying out parts.

HELPFUL HINT

Figure 1-8. Truck parts and dimensions.

Figure 1-9. Truck parts and dimensions continued.

Figure 1-10. Truck parts and dimensions continued.

STEP 4. Cut out your circular parts.

The first parts to be cut out after the layout is complete are the wheel centers and the arcs in the cab sides. If available, use a circle cutting attachment. With this attachment, your circles can be cut out quickly and accurately (Figure 1-11).

To begin, use a hammer and a punch to mark your circle centers, with the steel placed on a solid surface (Figure 1-12). Then, adjust your circle cutting attachment. Two settings will need to be made. First adjust the pivot point so that it extends 1/8 farther out than the plasma torch nozzle. Second, adjust the attachment so that the proper radius is set (1 for the wheel centers and 1-1/2" for the cab sides). When setting this distance, measure from the pivot point of the circle cutting attachment to the inside of the hole in the nozzle on the plasma torch.

Figure 1-11. a) A circle cutting attachment for a plasma cutter is a helpful tool for cutting smooth accurate circles and arcs. You need two hands to swing the arc and it can be tricky to learn to use properly. It may take some practice, b) Bottom view of the circle cutting attachment and inserted plasma torch.

Prior to actually cutting, place the pivot point in your punched divot and swing the arm a full turn to insure a full rotation can be obtained smoothly and easily. If this is not possible, the attachment height may need to be raised or lowered so that the torch tip rides approximately 1/8" above the metal. Also, insure that the torch lead doesn’t cause too much pull downward as you are cutting and that it does not bind on anything as you perform your rotation. If height adjustments were necessary, the arc distance will also need to be re-measured and re-set.

At this point, you are ready to cut. Set the pivot point in the divot. Be relaxed and light handed, which will allow movement around the circle to remain smooth and precise. The only part of your body that should be tense is the finger squeezing the plasma torch trigger (Figure 1-13a and 1-13b).

If you do not have a circle cutting attachment, hand cut out your circles as accurately as possible. Some grinding of the edges will be necessary after cutting.

Figure 1-12. Using a punch and hammer to mark circle centers requires a solid surface and a steady hand. When making your punch mark, hit the punch one time only. Back to back hits can give you two divots. If the divot is not deep enough from the first hit, reset the punch and then strike again with a single blow.

Figure l-13a. Ready to begin cutting a cirde.

Figure l-13b. Cutting a circle with a plasma circle cutting attachment.

Figure 1-14. Shade 5 cutting glasses.

SAFETY TIP

Plasma arcs produce dangerous UV rays. Wear colored safely glasses to eliminate damaging your eyes (Figure 1-14). When you drag cut, the torch hides most of the arc flash and shade 5 is adequate. When you are free hand cutting without a straight edge or circle cutter, you may want to use a darker shade for proper eye protection, depending on the amperage setting and thickness of steel that is being cut. Refer to your owner’s manual for safety specifications for your machine.

To eliminate the risk of fires, remove all flammables from the area. To reduce the risk of burns, make sure you are wearing the proper foot wear and clothing.

STEP 5. Cut the remaining sheet metal parts.

Next, collect a scrap piece of 1/4 flat bar at least 1 wide and some C-Clamp locking pliers. Clamp your sheet of steel to a sturdy table if it was pre-cut to size. Use the other locking pliers to clamp your straight edge to your sheet. To determine the distance your kerf will be from the straight edge when drag cutting, set up a test cut in a place where your parts are not laid out. To measure the distance to the center of your kerf, use a steel rule that measures in sixteenths of an inch (Figure 1-15). Use this distance to accurately place your straight edge for each cut.

During this cutting process, it is easiest to pull the torch toward you, rather than trying to push or go side to side along the straight edge (Figure 1-16).

Figure 1-15. Use a steel rule for measuring the kerf (width of your cut) and distance from your straight edge. In this example, it is 3/16 from the straight edge to the inside of the kerf. If you wish to leave the line, place the straight edge to the inside of the line and set it 3/16 from your scribed line.

Figure 1-16. In this example, the person cutting is set up to pull along the straight edge while cutting.

Note: These parts could easily be cut using a CNC plasma Cutter. If you choose this method, the same layout plan would still prove to be the most economical. However, if you haven’t used a plasma machine before, this project is a good way to learn