What type of drill bit..........

[pcgold]

......should I use to drill out a set screw?

I have a 1973 MGB. One of the mirrors is pooched and I have a replacement. I don't care what happens to the old one. There is a set screw that holds the base of the mirror to a gasket which is screwed on to the door.

The set screw is giving me problems. It is a slotted head. However, the two "sides"of the slot are pretty well gone and I can't get a screwdriver to bite.

I have tried to drill out the set screw. I have lots of different types and sizes of drill bits but nothing will even make a dent in it. It must be hardened steel.

So, apart from cutting off the mirror, what do you recommend?

 

[Davi]

You could try a left hand drill. If it bites it may even spin it out for you. Give it a good center pop and use plenty oil to cool

 

[Milton Shaw]

Mad Dog Drill bits will drill out that setscrew, they are hard enough to drill a file or hacksaw blade. Expensive but lifetime guarantee but will drill anything. I have used them to drill metals that other drill s don't even scratch.

 

[Warrenator]

Might be able to use a micro-torch to heat the set screw, thereby annealing it and making it easier to drill.

 

[countryraised]

Is it stainless? if so use a left hand bit and some Iodine. Iodine make stainless cut or drill just like mild steel.

 

[STClurker]

Is it stainless? if so use a left hand bit and some Iodine. Iodine make stainless cut or drill just like mild steel.

??????? I've never heard that one before

 

[Full Size 66]

Me too, I worked in a stainless shop on all kinds of food processing equipment. Most of it was fish related so corosion even on stainless was a problem. We used oil of different types but I never saw iodine...

 

[bgott]

A carbide bit ought to do it. Since you don't care about the old mirror, try using a Dremel tool with one of the little cut-off wheels they sell for them and cut a new slot in the set screw. Then see if you can back it out with a hammer impact.

 

[dtt454]

cobalt drill bits, they are not to expensive and they work real well.

 

[Rogue1987]

I am also a fan of cobalt drill bits.

 

[pcgold]

No way could I drill it. I used my Dremel and actually cut off the entire portion around the grub screw. Took about an hour and quite a number of cut off wheels, but if came off. Thanx for the suggestions.