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Originally Posted by DampRobot
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?
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Could you take a flat-tipped punch and knock the remnant through the hole? For closed-end or tight rivets, or parts you can't hammer very hard, I suppose you could grind it flat with a die grinder or similar tool, then centrepunch it before drilling. I've never had occasion to try either one.
Quote:
Originally Posted by DampRobot
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?
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It varies: check the manufacturer's specifications. If those aren't handy, look at McMaster-Carr's blind rivet section, and try to find something similar, and use the drill recommended. It's probably either 0.192 in–0.196 in (#11) or 0.201 in–0.204 in (#7).
Quote:
Originally Posted by DampRobot
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?
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Presumably you're not exposing the heads to any unusual force that would cause them to do anything but spin on the drill bit. So I don't see any problem with that. The worst case scenario is that they are held tight, and the drill drills through them, enlarging the hole. I can't imagine why that would be especially bad either.