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Off Road Fabrication Tools - Fab X Four

Posted in How To on January 1, 2009
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In this off-road world, we are surrounded by the creative fabrications from skilled builders. These builders take raw steel components and assemble the vehicles that we use to explore and challenge our favorite dirt terrain. The technology of today has brought forth tools that are widely available to shops and home builders alike.

Here we'll discuss four different fabrication tools you could use in your home shop when building your off-road rig. The tools help you to build a wide variety of vehicle components and do so adding strength and good looks to the structures.

Tubing Notcher
All manner of off-road vehicles use some kind of tubular structure. It might be a tube bumper or light bar, spare tire carrier, rollcage, or a complete chassis. Where there's tube, there's the need to mate one to another in a clean and structurally sound manner.

When one tube is butted to the rounded outer wall of another, it needs a circular cut made in its end to mate gap-free with the other tube. Such a circular end cut is referred to as "fishmouthing" the tube.

Other notching methods include the use of a sanding belt on a dedicated tool and there are hydraulic powered punches that can cope the end of a tube. Production or higher end fab shops may utilize a CNC laser cutter to fishmouth as needed.

Tube notching is used so that converging tubes mate together with a small gap for welding. In the case of a joint that is to be TIG welded, the gap between tubes must be quite small as TIG welding (as compared to MIG welding) uses minimal filler metal in the mating joint. When several tubes converge at a single point such as on this race chassis, it will be necessary to notch some tubes twice on opposite sides.

Typically, the best way for a home fabricator to fishmouth tubing is with the use of a portable notching jig. This device holds the end of the tubing in place at the proper cut angle and has an arbor that accepts a hole saw used to make the curved cut. A portable electric drill is usually used to power the hole saw in the arbor. The notcher can be held in a vise or bench mounted.

Heavy duty tools such as the Ultimate Tube Notcher from Mittler Bros. uses a large TiN coated mill bit to cut the face of the tubing very accurately. The tube is clamped into a compound vise set to the desired cutting angle, and then the tube is fed into the rotating cutting bit.

Dimple Dies
Sheetmetal is used in a variety of ways in automotive construction. It can span and enclose large areas such as a hood might do. Or, it can be stamped and bent to form a skidplate or battery tray. Flat steel itself gets its strength from its thickness, and as the span size increases the sheet has more flex and rigidity decreases.

However, there are ways to stiffen a piece of sheetmetal or steel plate with the use of 3D shaping. One way to increase the stiffness of a sheet of steel is with the use of dimple dies (also called flanging dies). First, a hole is drilled or punched in the panel. Then a two-piece die set is used in a press to flare the hole outward on one side of the sheet. These actions lighten the panel with the removal of material and increase the rigidity of the panel. The portion of the metal that is flared is stretched and the third dimension to the sheet stiffens it.

This means that thinner material can be used to build structural components. This equates to weight savings. When used extensively on a vehicle such as a trophy truck or buggy, weight savings is significant. Lower weight means more horsepower per pound, better vehicle handling, and typically better reliability when taking a pounding in the dirt.

Dimple dies come in a variety of sizes from about half an inch up to about six inches in diameter. This dimension refers to the size of hole needed to start the die. Once pressed, the hole is flared and the diameter increases a bit beyond that dimension.

To dimple a panel, a hole is first drilled in the sheetmetal. The dies (one male, one female) are placed through the hole above and below the sheet and then a press is used to expand and stretch the metal into the flared dimple shape.

Here is an example of a structure on the front of a race truck used to support the hood structure over the front suspension. It's composed of several aluminum sheets that have been bent and welded together. The use of material in several planes makes it stronger and the addition of the dimple die holes lightens and also stiffens it considerably.

Dimple dies can be used in a standard automotive press, arbor press, or in this example of a homebrew dimple die machine. Chris Villareal used a scrap piece of DOM axle tube welded to a chunk of thick box tube and an upper support arm braced with additional metal pieces. A 20-ton hydraulic bottle jack serves as the power to flare sheetmetal.

Brace plates are often used on a chassis to add strength where two tubes come together. In this location a steel sheet spans two tubes. The dimple die holes increase rigidity and allow the use of the thinner sheet.

Bead Roller
Another method that is used to stiffen larger, thinner body panels involves the use of a rolling die to put relief in a panel. This can be done with a tool called a bead roller. Essentially, the sheet metal is clamped snugly between two steel roller dies that are then rotated. As the sheet travels between the dies, they impart a raised pattern to the sheet. This stretched and raised metal adds rigidity to the sheet much like the dimple die work.

Auto builders use a similar technique to add stiffness and strength to sheet panels. The back of this truck cab has intricate channels stamped in it. The 3D stamped surfaces break up the large flat expanses and greatly increase the rigidity of the panel. The increased stiffness means the manufacturer can use a lighter gauge metal than would normally be needed if the panel was left flat.

This is a hand-operated bead roller manufactured by Williams Low Buck Tools. The unit can be clamped in a bench vise, then the rollers are tightened against the sheet which is fed forward or reverse through the rollers by turning the crank handle by hand. Bead rollers can use a variety of roller die shapes and the dies can be quickly swapped from one to another.

Here you can see a piece of aluminum sheet pinched between a set of round bead rollers. This is a common pattern used on body panels and produces a raised half circle profile that may vary from about 1/8 of an inch to 1 inch in diameter. The raised round bead adds style to the panel and stiffens it considerably. This can also help in areas such as roof panels to quiet the sheetmetal flexing that often occurs without some method of stiffening.

This roller die set is called a step roll (or flanging die). It creates a step in the metal such that the edge could be butted and overlap another adjoining sheet and provides a smooth joint of the same level on one side of the mated sheets. There are quite a few other die varieties, including radiused tank roll dies. These put a rolled curve on the edge so when mating two sheets at a 90 degree angle the edge forms a curved section instead of a sharper 90 degree bend.

While economical and often a good choice for the occasional user, a hand operated bead roller can sometimes be a challenge for a lone person to operate, especially with larger panels. Operation requires turning the roller drive while simultaneously guiding the sheet through the roller dies. A power bead roller such as the billet aluminum version from Mittler Bros. will have an electric motor powered drive controlled via foot switch, leaving both hands free to guide the sheet.

As bead rollers increase in size (and cost) one advantage gained is that of throat depth. This is the dimension that tells you how deep you can place a sheet into the roller. A deeper throat depth means you can roll patterns on larger panels or further in from the edge of a panel.

Sheetmetal Brake
If you have plans to build bracketry or sheetmetal structures, it's a good bet you'll want to bend some of those flat sheets of metal. Here's where a sheetmetal brake can help.

There are two basic kinds of brakes: straight brakes and box & pan brakes. A straight brake simply has the ability to bend the whole length of a sheet upward at most any angle. A box & pan brake is similar but has movable sections of various lengths to allow you to make the first bend, then follow with additional bends as if building a box. The movable "fingers" allow clearance areas where no bending takes place along the length of the sheetmetal.

You can stretch your home fabrication skills and proficiency with the addition of metal working tools. We've detailed a few that might just make your projects easier, more fun, and yield a higher quality result. Good luck with your next home build!

For thin steel or aluminum work, small benchtop brakes are available at reasonable prices. Either thick material or longer sheets require beefier brakes, and many times tool capacity can be traded between the two. For instance, if you have a 24-inch brake rated to do .060-inch steel, you can often bend thicker pieces of steel that are narrower, to a reasonable degree. This small Low Buck Tools plate brake can bend thick plate brackets up to six inches wide.

Large box & pan brakes with multiple moveable fingers are versatile and capable of producing a variety of boxed structures. Complex bend sequences can turn flat sheet into a number of useful items.

Need a simple brake for occasional use? We had a project where we needed to fab a sheetmetal radiator shroud. In about an hour we built a simple homebrew brake from some scrap angle and other steel stock and hardware we had lying around. You can find simple plans in tool building books and on the web.

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