Riveting....this article will probably lean toward the literal sense of the word as opposed to the figurative version!
Riveting has always been one of those pinball skills which many do not want to bother with. You need some special tools, and there is always a fear of doing damage to the nice, new parts you are trying to install.
First, lets talk about rivets. What you are looking for is known as a "semi-tubular rivet". This is a solid body rivet with a smooth exposed top, and a hollow base that will be peened or rolled over to clinch it into place.
You do not want to use pop rivets! Pop rivets work by pulling a pin with a bulbous head on it through the body of a tubular rivet. Once the head bottoms out in the rivet, the pin will snap off. The problem with these rivets is two-fold. First, they are ugly and not-OEM looking. Second, they expand the body of the rivet in a manner that could easily deform or crack your plastic parts. Pop rivets have their place in the world, but we can do better on our pinball projects!
The Commandments of Successful Riveting
Now that we know a little more about the two main kinds of rivets out there, lets talk about a couple very important guidelines when using a semi-tubular rivet.
Commandment 1: Thou shalt use a backup washer any time you are clinching against plastic. Rivet backup washers are usually half or more of the thickness of a standard washer. Thin washers are very important in places like ramp flaps, where the clearance against the playfield is tight. A full thickness washer will possibly keep your ramp from sitting flat on the playfield. Backup washers are available on my site, on in bulk from Hanson Rivet
Commandment 2: Thou shalt drill holes at least 1/64" oversize from the rivet you are using. 1/8" rivets are the main diameter used on pinball machines. I always drill my holes 9/64" when riveting ramps for a couple reasons. First, it gives you a bit of wiggle room in case the drill moves a bit. Second, if you are too hard on the clinching process and you wind up expanding the body of the rivet a bit, you still are not putting later stress on the hole you drilled. Remember from the diagram above, the rivet is to act like a clamp, we do not need or want to expand the body size of the rivet at all.
Commandment 3: Thou shalt use the correct length rivet for the job. If you do a lot of work on machines, you are going to wind up having a variety of rivet lengths on hand to pick from. Rivets come in 1/32" length increments. For me, it is easier to address these lengths in those 32nd of an inch increments, as that is the way I order them. So yes, 8/32" is 1/4" of an inch to the rest of the world, but I am still going to call it 8/32" when talking about riveting. I usually keep a range from 6-32 up to 10-32 on hand, which seems to cover just about everything except for switch stacks. More on those later! I have these sizes for sale on my site in small quantities, or you can order them directly in larger quantities from Hanson Rivet.
Sub-note: I only use nickel plated brass rivets. Why? They are OEM looking in most cases. They do not dull or rust. And more importantly, they are very forgiving compared to steel or aluminum. Brass is soft and pliable, and requires less force to successfully clinch into place. I do not recommend steel rivets to anyone just learning how to rivet. Especially if you are using the hand punch method. There is a much greater risk to overstriking the rivet and ruining your finished part. Hanson does not list these nickel plated brass rivets on their site, you will have to call them and ask for them over the phone.
Selecting the right length
So now you know the basics of semi-tubular rivets, lets dive into how to pick the right length.
This chart was pulled directly from the Hanson Rivet web site:
"A"= the body diameter, which is most likely going to be 1/8"
"Length"= the overall length of the rivet, in 32nds, under the head
"D"= hole depth; this is .089" on 1/8" rivets
The hole depth is important, because if the sum of the parts you rivet together is thinner than the length minus the hole depth, you are going to have a hard time getting the rivet to clinch tight. Ideally, you want the parts to be about 1/32" thicker than the length of the hole depth. Don't forget to add in the thickness of the backup washer!
For example: You are riveting a flap to a ramp. Your ramp measures .100" thick, your flap is .006" thick, and your shim washer is .020" thick. This means you should be .125" thick or so. "D" is .089, and we can subtract that 1/32" overage from that number, which gives us .057". So add .057" to the .126" to get a total length of .183". Divide that .183" by .032", and you get 5.71 32nds of an inch. I would choose the 6/32" length rivet for this application.
You do not need a fancy measurement or equation to figure out what size rivet to use once you get the hang of it. Here is an example of a rivet that is too short for the job. The clincher was unable to fully roll over the rivet, and the parts will not tighten up completely.
(Above: Too short)
(Above: Rivet did not fully roll over, creating a loose joint)
(Above: Correct length rivet)
(Above: Properly rolled rivet, resulting in secure fit)
This wraps up the first installment of riveting information. Next, we will dive into riveting squeezers and presses for every budget.