window motor rivets

[sd_iconoclast]

I have a '91 EB and a 96 XLT.
The drivers window motors went out at the same time.
I bought two sets of beck/arnley window motors with regulators.
The '96 was easy.
The '91 is giving me big problems because I cant get out the rivets that hold the regulator to the window.
On the '96, the rivets were soft aluminum and I was able to drill them out easily.
The rivets on the '91 are much harder. Even though I was able to put a good dent in the center of each rivet with the punch, I was unable to drive out the centers.
I tried drilling them out but it is like they are made if hardened steel.
I ground the heads off the three rivets that hold the motor using the angle grinder but the two rivets that hold the window to the regulator are not accessible with angle grinder.
What did you guys use?

 

[ChildIdenticant]

The rivets are definitely not made of hardened steel but yes they are more difficult than the 2nd gen. I've seen 3 different kinds of rivets on these. 1 can be popped with a good 1/8 punch strike. For those that can't, use a pin point punch directly in the center to start. Make the strike good enough to allow using a 1/16 drill bit without it walking. Use a pecking action to drill through. Then do the same with a 3/32 or 1/8. Just keep stepping up bits, remember to peck. The rivet will likely free spin before you can actually drill it out perfectly. Use that last bit slightly tilted to catch/grip the rest of rivet. Then use the drill to force the mount bracket to cut through the rest of the rivet from it's outside diameter . Don't be shy about that first pinpoint strike, can get it down to ≈5 minutes a window.

 

[410Fortune]

Grind the heads off flush and punch them out

Otherwise a stepped drill bit will make short work of them 9 times out of 10

 

[sd_iconoclast]

I bought some new drill bits but they are not making a dent.
I had my son pound on the punch pretty hard while I held the window. No luck.
I think I am going to try taking out the window to the point that I can reach the heads and grind them off.