Riveting Tips

[DampRobot]

I thing that among all the pre-kickoff game hint madness, it's about time for a good old technical thread.

My team does what would probably be considered a very "West Coast" frame setup (2x1 aluminium box tubing, etc) but tends to prefer using 3/16" rivets over welding. We use a lot of rivets, probably on the order of a few hundred in a serious weekend of building, so I thought it would be good to get the CD perspective on a few small problems with rivets that have bothered us in the past.

First, we sometimes see the mandrel break about halfway down (instead of inside the rivet body like it's supposed to) when we're installing a rivet, which gets to be a real pain. They stick out, look ugly, and make it very hard to take out the rivet. Is there a root cause to this type of problem? Is there some sort of technique that can keep this from happening? If the mandrel does break halfway, what's the best way to uninstall the rivet? For normally installed rivets, we usually just take a #10 drill and drill through the center of the rivet. However, with the nub of the mandrel still sticking out in the center of the rivet, it becomes very difficult to start the drill on the center. Is there another way to remove this type of rivets?

Second, what drill size is the "right" size for 3/16" rivets? On our team we've used everywhere from 3/16" (fractional) drill bits to #6 number bits. The #8-6 bits are nice because they're also clearance for 10-32 screws, but they also produce loose fits for the rivets, which can sometimes make out frames wobbly. Is there a correct size (or at least best size) for 3/16" rivets in FRC?

Finally, when we drill out rivets, the lazier among us (including yours truly) like to let the heads of the rivets stack up along the drill bit. If we're drilling out ten rivets, it can become a pain to clear the drill of each head individually, so we just let them stack up. However, some of the mentors have said that this is bad for the drill bit. Is this baloney or the wisdom of an experience machinist?

If other people have cool/interesting tips about rivets in FRC, feel free to share them on this thread too.