We have rivets to hold sheets of metal in larger sheets, or in interesting shapes (e.g. tank cars or locomotive cabs). You don't really want to dirll holes for and insert those hundreds or thousands of rivets in your model, but you want it to look like a real one when it's done, so you must find another way to simulate them. The typical method is to use a tool called a rivet press, which embosses the metal or plastic sheet with a hemispherical shape which looks just like a rivet head on the surface of the sheet. When it's done right, it's very convincing. When it's done poorly, it can look like a skin disease on your model -- little pointy pimples or pocks which bear no resemblance to a rivet at all.
If you have a drill press, you can make a rivet press for virtually no cost, but which works beautifully. To construct this tool, you need to have or make three things:
The general arrangement of the tool is shown in figure 1.
The principle here is to force the sheet material into a hole the size of your prototype's rivet head. You will press it from behind with a forming tool which will give it a hemispherical shape, and which will press the shoulder of the bump against a forming surface to give it a sharp edge.
The punch in the drill chuck is made of 1/4" brass rod. Steel
is theoretically preferable, but the brass one I made early on has held
up remarkably well, so I haven't bothered to make another. If you're
going to be punching something harder than brass or styrene, use steel.
The metal die is made of a piece of 1/8" x 1" x 6" steel I had in my
scrap box. Anything harder than the material you punch will do.
Before you start drilling, you must first choose the size of the rivet
you're going to make. A 1-inch rivet would be .049" in 1:20.3 scale,
which we'll call 3/64" (= .0469") for purposes of choosing drill bits.
Mark and drill a series of evenly spaced holes in a straight line, using
a 3/64" drill bit. If you don't have an X-Y table for your drill
press, then keeping a lot of holes exactly in line will be difficult, so
just drill two. (If you do have a X-Y table, then the fence is superfluous
and you can just clamp your die to the table.) Drill the holes all
the way through, or your rivets may bottom out in the hole, and end up
looking like drill bits sticking out of your material.
The taper of the rod away from the shoulder is for fence clearance.
You want the punch to press the metal from the rear to form it into the desired shape, but not to cut, thin or stretch it. Look at the drawing, which shows a cross-section of the die, with a rivet pressed into the hole. Notice how the metal is stretched slightly to go into the hole, but is effectively the same thickness as the flat sheet. So, to make your punch you must also know the thickness of the material you'll be forming, then subtract two thicknesses from the size of the hole to find its diameter. Let's say you're using .015" thick brass. There will be two thicknesses of .015" on either side of the nose of the punch, leaving .016" for the nose. That's the diameter you must make the nose of the punch. You want the depth of the nose to be the diameter of the rivet. (Figure 3.)
There are two methods (at least) for making punches: turned and fabricated. Turning involves using a lathe, so if you have one, use it to turn the nose of the punch to the calculated diameter and depth. (It's possible to do this with files and your drill press, but it's going to be very tedious!) Turn the nose from a larger piece of rod, leaving it as a cylinder, and turn the surrounding material flat and square. This permits the shoulder of the punch to press the metal down flat against the die, separating the rivet head very sharply from the flat sheet. Set the lathe on the slowest speed, and file the edges off the nose wtih a fine flat file. The end should be as close to hemispherical as you can manage. An OptiVisor or other magnifier will be helpful here. The flat part of the shoulder needs only to be a sixteenth of an inch or so in diameter -- a little larger than the size of the rivet head. I tapered my punch away from this shoulder to permit forming rivets very close to the fence (figure 2); you could also make the punch from a smaller bit of rod if you find clearance is a problem.
Fabricating a punch involves drilling a hole in the end of the large rod you're making the punch from, which requires some care. Calculate the size of your punch nose, then see how close you can come to that diameter with rod or wire. In the example above, you're going to have a very thin nose, so piano wire (or a guitar string) might be your best bet. These are available in hobby shops (piano wire) or music stores (guitar strings) and are sold in increments of .001", so finding the right size will be easy. Cutting it is harder; you will need some good wire cutters, though the cutter on your needle-nose pliers may be up to it. Mark and drill a hole in the end of your large rod. The hole can be fairly shallow -- say, 1/4 inch or less. Clip off some rod or wire, measure its length with your caliper, and insert it into the hole you just drilled. Measure how much sticks up, and you can determine how much to cut off so the right amount will stick up above the end of the rod. Cut off the right amount, then use CA glue to set the wire into the end of the rod to make the nose. To round the nose, chuck the rod into the drill press, set the tool to its lowest speed, then very, very carefully touch a fine file to the edge of the nose. This is a delicate operation, and one that really requires an OptiVisor or similar magnifier. Otherwise, you're working blind, which is not generally considered good practice in a machine shop. But it can be done with a light touch and some care, or you can just roll the rod by hand on the table top while you file the nose.
The guide on my press is made from 1/8" modeling plywood scraps. Use something the same thickness as your die, and be sure the slot for the die is square with the edge of the fence. To do this, lay two strips of wood on either side of your die, then lay a fence piece (with glue on the back) on top. Square up the fence and clamp the whole assembly until dry. I used a heavy-duty stapler to put a couple of staples into mine, but the glue alone should last. You may wish to mark ruler lines along the fence, over the die slot, or on one of the lower pieces, to measure the distance from the fence to the die holes.
Now, you have the three parts made, so on to operation. Chuck the punch in the drill press and adjust the table so the end of the punch about an inch above the surface. Slide the die into the guide and adjust its position on the table so that when you bring the punch down it's exactly in one of the holes you drilled. Actually punching a rivet before clamping will help center the die under the punch. Holding the die in place with the punch, adjust the fence until the die holes are the right distance from it. Clamp the fence and die plate down to the table (figure 1).
Hold your material against the fence, lower the punch gently with the drill's quill handle, and press the punch into the metal with the minimum force required to form the rivet. Even fairly thick metal sheet (.025" or even thicker) can be formed in this way without slamming the punch into the sheet. You'll know you're pressing too hard or fast when the rivet "head" ends up in the die hole and there's a corresponding hole in your sheet. Press the punch down until the shoulder area is down on the sheet and presses it gently against the die plate. You should practice on some scrap material every time you start to use the tool because, I have found, the right touch is a matter of practice, and very few of us punch enough rivets to stay in practice all the time. It comes back very quickly, though.
Above, I recommended drilling two or more holes in your die. This arrangement acts to space the rivets exactly as you form them, in the following way: after you punch the first rivet, move it into the adjacent hole until it snaps into place. Then punch another, and move it into the hole. As you can see, the third and every following rivet will be spaced exactly the same distance from the others. There is really no need for an X-Y table or other automatic advance devices. Simply sliding the rivet a tenth of an inch into the next hole is as easy and fast.
That's all there is to it. The tool is very simple to make, and
absolutely simple to use, but produces outstanding results. If you
need to make different sizes of rivets, you'll need to make a new punch
and drill new holes in the die plate. But when you have done it once,
making additional parts will go quickly.
The rivets on the brass tender in Figure 4 were formed with the tool
in the other photos. The sheets were drawn in a CAD program, printed
at full size, then glued to a sheet of brass with a light coating of spray-on
rubber cement (photo cement). The sheets were cut out by following
the lines on the drawing with metal shears, then the riveting tool was
set to the fence held the printed rivets on the paper under the punch.
The tender's sides and top were embossed with rivets in about 15 minutes.
Last updated: 9 September 2000.