drill bits for drilling sheet metal

I have to drill out some 1/4" rivets to get my power window motor out. I’ve done this before and it took a very long time, probably because I was using the wrong type or drill bit. Well, it’s time to do the other window, so what should I be using? High speed steel bits?

What type of bits were you using? Rivets are usually mild steep or aluminum. The somewhat fancy Ti-nitride bits would work, but a good high speed steel twist drill bit would work as well. I’d use a slower speed and maybe oil the bit (though this probably won’t work when drilling sideways) to keep it cool.

If there are any aviation surpluses around where you live, I’ve heard that they can be a good source for good bits.

Pop rivets or solid?

Funny I never thought of that. I work at an airport and we have an aircraft maintainence department. I was using what I guess were wood bits. The rivets I have to get out are bigger than usual and I can’t get to the back of them, I have to go through the rounded-off dome end. 4 times.

Sears (Craftsman) sells some Zirconium Nitride bits that work very well for this sort of thing.

Uh oh, sounds like solid rivets. You might try putting something heavy on the backside to buck while you tap the front with a center punch, the start drilling with a smaller starter bit, then drill the head off with a bigger bit.

The problem with drilling out rivets isnt the type of bit needed, most any sharp bit will work. Its that they tend to SPIN when the drill is applied to them.

Apply some pressure to the back of the rivet (to prevent spin) and then use a high speed drill motor and get the drill bit up to speed BEFORE you apply the drill bit to the rivet head. Repeat if necessary.

In other words, don`t push against the rivet head with the drill bit and then squeeze the trigger. You want the bit already spinning at a high speed before you bear down.

Be very careful though.

I see you said that you can`t get to the back of them.

If the method I described doesn’t work you can always use a dremel tool with an abrasive tip on it and just grind the head off the rivet. Very effective also.

Rebuilt both power window motors in the catmobile, drilled out the rivets starting with 1/8" HSS split point bits (increased to final necessary diameter), dipped in cutting oil and run slow, with gentle feed.

The most valuable things I’ve learned about tooling are: sharp, oiled, and easy feed rate (pressure).