I had to drill a large number of 1-1/4" holes 15 inches deep in granite
to place a dock two years ago. The local Makita rep offered me the loan
of a Makita HR3851 rotary hammer and with it I was able to drill them
quite easily.

Your compressor isn't big enough to run a pneumatic drill of any size
but would be useful to clean out the holes. The bit doesn't lift
granite dust well from deep holes. I fashioned a 1/4" diameter copper
tube that would reach to the bottom of the hole and attached it to an
air chuck. Every couple of inches I'd pull the bit back, insert the
tube and clear the hole. (Eye protection and a dust mask were needed.)
Not a bad job. No more than 10 to 15 minutes per hole, including beer
breaks.

RB

klim wrote:
I need to drill many (50 to 100) 1 1/2" diameter holes 6" deep in
solid rock for steel T-posts for a fence and I haven't decided how to
go about it.

What type of bit/drill combination would be most cost effective?
Electric drill (size?) with core bit?
Pneumatic drill with impact bit?
Other combo?

The location is far from power so the job would require a portable
generator or a compressor if a pneumatic drill was used.

I have a 2hp 20 gallon compressor - would be sufficient to run a
pneumatic drill to drill the 1 1/2" holes?