Historically, our team has been using 1/4in rivets for every application, but I’ve recently started looking into using 3/16in rivets instead. For 1/4in rivets, we typically have to drill out a 3/16in hole to 1/4in and then rivet it using our pneumatic rivet gun because it is simply impossible to rivet it using a hand tool. My question is if 1/4in rivets are overkill and we would be better off switching to 3/16 rivets next year to save ourselves the hassle.
TLDR: Yes, that would be a good idea. Frankly, 3/16 rivets are overkill for many FRC applications but it’s a much more reasonable standard, as you’ve noticed with predrilled 3/16" holes.
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We’re firmly in the 3/16" rivet club. Our “standard” is 10-32 screws if it needs to come apart, and 3/16" steel rivets if it doesn’t. We usually use a pneumatic riveter in the shop, but every new build team student first gets to set one rivet with the hand riveter. They treat the pneumatic tool much more nicely from then on.
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1/4 rivets are overkill, 3/16 are also overkill. We use 1/8 rivets everywhere and tend to break gussets and tubes before we have a rivet failure.
Also, highly recommend the Milwaukee 12V rivet gun. We picked one up last season, it’s much better than the pneumatic river guns we’ve used.
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We’ve switched to the Milwaukee battery powered rivet gun and it is a game changer. Highly recommend.
We’ve also switched to keeping a sharp cold chisel in our tools to remove rivets instead of drilling them out so we never risk expanding a hole.
Note: Using a cold chisel is extremely fast but does require someone who isn’t going to gouge into the material. Make your chisel sharp and ground to be able to wedge under the rivet and keep your chisel angled as flat as possible to avoid damaging the material.
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3/16" rivets are great because you can use them with 10-32 screws interchangeably, simply by drilling .196" holes everywhere. This makes mounting things to an existing hole pattern easy and you don’t need to think too hard about what hole size to use in a design.
I get best results with rivets by adding one bolt per fixed member of a riveted joint. So every corner gusset gets filled with rivets, and then I add 1 screw through each tube the corner gusset is connecting. This ensures that the screw helps take up shock loads while the rivets drive most of the strength of the joint. I used to have rivets loosen up all the time, and now it seldom happens.
Pneumatics rivet guns, drill attachments, and independent electric rivet guns are all great to avoid using hand riveters, which is still a pain on 3/16" rivets.
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Al or Steel is probably more significant than the diameter
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Both matter. I would avoid full steel rivets because they are a pain to drill out. I’m not a huge fan of steel mandrels either because they don’t always make it out, and then it’s a big pain to remove them.
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We have a pneumatic rivet gun in the shop, but needed to retread a whole set of wheels with rivets at comp. After watching our students struggle for a while, our pit neighbor handed us their Milwaukee electric rivet gun. I put in one rivet, then picked one up on the way home at Home Depot to have for the second day of competition. 
We’ve mostly used 5/32 rivets because of the versaframe hole size. We started having issues with the strength though and switched to a lot of 3/16 this year, and because we got some rev extrusion with 3/16 holes, I do like them better. Our standard bolt is 1/4 20 for no good reason except we can buy them buy the pound, and that’s what we’ve used for ever. I really like the idea of switching to mostly 10-32 and 3/16 rivets to use the same hole size!
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The Milwaukee rivet gun is possibly our best purchase as a team. Most of the time we match drill all our riveted plates to the tubes. We undersize the gusset holes to 3/32, line everything up and clamp it down to a fixture table, and drill and rivet as we go.
A few of our assemblies we pulled out the Clecos to rough assemble everything before we riveted. We got a set similar to this on Amazon a couple years ago, also a great pick up depending on your workflow.
K-SERIES MASTER CLECO SHEET METAL FASTENER KIT w/Mesh Carry Bag (K1MSTR)
Thanks for all the helpful replies! We will look into switching to 3/16in rivets next year and I’ll see if we can afford that electric rivet gun as well. If anyone has any advice on the best place to buy rivets that would also be appreciated.
I’ve used blindrivetsupply.com in the past. I typically go for a aluminum body, steel mandrel rivet.
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Our team uses 3/16 rivets to hold our A-frame together, and it’s certainly not ever going to move. I can agree that even a 3/16 in rivet can be overkill for FRC.
You can make your riveted connection stronger by any (or all) of three methods:
- Bigger rivets (my middle favorite)
- Steel vs Aluminum (my least favorite)
- More rivets, provided you have enough base material left (my favorite).
Also, do not use rivets on joints where the rivet will be under tension (that is, the plates it is joining are being pulled apart). If there’s significant tension, use a threaded fastener, or re-design the connection so that force is coming out as a shear force on a rivet in a different orientation.
I usually use 5/32" - unfortunately, this does mean you will want to have plenty on hand because home centers don’t carry them, and hardware stores usually don’t stock very many. I’ve been happy with https://www.hansonrivet.com/.