Building the “Key” Rivet Bar
By Steve Hill, CO

In the most recent edition of “Tech Corner,” I highlighted several tools, one of which is called “the Key” by some technicians who liken its general shape to the skeleton keys of old. Although Tom Adams, a machinist from Missouri, will make it for you if you wish, talented technicians with access to a welder can make it for themselves. Just follow the steps below.

The advantage of the Key over other riveting bars of its type is that it’s extremely heavy-duty. If you’ve ever pounded on smaller, lighter bars and felt them flex with each hammer blow, you know what I mean.
The Key is also more versatile, with a large flat anvil on one end and the ability to apply different heads at the other.

It’s not a complicated piece of equipment. You can change the dimensions or use different materials to suit your own needs. All you need to know is the basic design and an understanding of how you might use it. Add some steel (along with your welder), and you have yourself a strong and versatile rivet bar.

Materials
The only thing you really need is some steel, but you’ll want to get it cut to suit your needs. Unless you enjoy spending hours cutting steel with the tools you have on hand, this will save you a lot of time and effort. The following materials can be found anywhere that sells steel to machine shops; companies like Grainger and McMaster-Carr come to mind. You can probably pick these items up at local supply houses.

To start, you’ll need a 16-inch-long section of 2-inch-diameter steel rod for the main body of the Key. That’s a big old honkin’ piece of steel! If you can’t get 2-inch steel rod, get it as close to this size as possible. Just remember that if it’s too big, it may be difficult to do delicate work—and if it’s too small, it will likely flex when in use, diminishing its usefulness.

Next you need something to make the flat anvil on the top. Try a 1/2-inch-thick steel plate cut to 2 inches by 6 inches.

Again, having it custom-cut to your dimensions will save you a lot of cutting. Half-inch steel plate is a lot smaller and easier to cut than the 2-inch rod is, but it’s still an awful lot of work. If you’re having the rod cut for you, you might as well get the half-inch plate cut as well.

The final section is the part that makes the Key so unique. Weld a 1/8-inch to 1/4-inch-thick steel plate, approximately 6 inches by 7 inches, to the bottom of the 2-inch rod to give the Key its key-like shape. This relatively thin section of steel straddles the screw arm of your vise, and its square inside shape prevents the Key from rotating when hammered upon. Since this thinner steel is easier to shape, you may be able to cut it yourself with standard hand or power tools.

Preparation
You will need to shape each of the three sections of steel before welding them together. The rod needs to have a 1/4-inch hole drilled about a 1/2-inch back from the round anvil end. This hole will accept the different anvil heads used for riveting and hammering.

Since the 2-inch-thick rod is too large for many riveting jobs, you should trim it down to a smaller shape. This will allow you to work on small plastic cuffs more easily. Starting about 4 inches back from the round anvil end, cut or sand a wedge-shaped section off to the middle of the rod, then taper the end by removing the corners that remain.

The 1/2-inch by 2-inch by 6-inch piece will make up the flat anvil section. All that you need to do to this piece is create a small, 1/2-inch round divot somewhere on the top side to allow copper rivets to be contoured into a truss head shape. Locate this divot wherever it is most convenient for you to work with. Bevel all of the edges to remove any burrs and sharp corners.

The 6-inch by 7-inch key-shaped section holds the whole thing in the vise and is attached to the bottom of the 2-inch rod. A 3-inch by 3-inch square slot is cut out of the bottom edge, allowing it to be placed around the vise’s screw arm. If the screw arm on your particular vise is of a different size than this, make the cut accordingly. Some screw arms are round, but this design works best if the screw arm is square, because the shape prevents unwanted rotation.

Welding
If you like to weld, here is where the fun begins! Position the key section at one end of the rod, and weld it perpendicular to the hole drilled at the round anvil end. Hold everything square and level. It’s best to have at least 9 inches of 2-inch rod extending from the key section so that it can reach deep inside of prosthetic sockets.

Weld the flat anvil section on top with about one-third of its length hanging over the end of the 2-inch rod. Keep it centered and square with the rest of the device, of course. It wouldn’t do to weld the anvil on an angle, making the hammer skip off with each blow.

Accessories
The anvil hole drilled at the round end should be able to accept a 1/4-inch shank. If it can’t, ream it out a little bit so that a 1/4-inch shank slides in and out freely. Now you can make any manner of anvil head you desire.

These six anvil heads made up the accessories first described to me, though you may discover more:

•    Three of the anvil heads are used for relieving pressure points on thermoplastic orthoses; two are made       of Delrin plastic and one is made of steel coated with plastic.
•    Another anvil head is made from a 1/4-inch hardened steel bolt that has a beveled head for riveting.
•    The same method of manufacture is used to construct another head, which is then covered with a layer
      of hard rubber and employed to punch holes deep inside of leather cuffs.
•    The last one is just a section of steel rod turned down in a lathe to the desired shape, and used as a          long anvil for riveting into deeper recesses of prosthetic sockets.

Use your imagination to come up with anvil heads to suit your specific needs.

Although this device is supremely simple, it’s not the easiest thing to make. Such large pieces of steel require special equipment to shape and weld properly. But if you have the wherewithal, it’s well worth the effort. If not, you can always e-mail Tom Adams at t_adams1021@yahoo.com and have one made for you.  

Steve Hill, CO, is secretary of OPTA and CEO of Delphi Ortho, located in Asheville, N.C. and on the Web at www.delphiortho.com.