How Can I Drill Into Hardened Steel Calipers?

[Jeb1234]

I'm trying to mount a cheap Lowe's digital caliper on my milling machine's quill for a quill DRO.

I've gone through 3 drill bits and two hss end mills trying to get a hole for a 8-32 screw.
How in the heck can I drill this stuff? I'm going with very slow rpms, cutting fluid and trying to put plenty of pressure on the feed but all I'm doing is dulling bits and end mills.

I can't heat it to remove the temper because I don't want to risk damaging the electronics and I don't really want to take it apart if I don't have to.

 

[dlane]

What kind of mill is it, Enco sells a kit to fit a caliper to BP type mills .
Got a pic of mill ,

 

[Jeb1234]

It's a Precision Matthews PM935TS. BP clone. Here's a stock picture of one.

 

[talvare]

I recently did a similar thing for my lathe tail stock. Just used a center cutting carbide end mill and it went through like it was mild steel.

Ted

 

[TOOLMASTER]

i just made a mount block with a slot to put it through . hold in place with set screw

 

[T Bredehoft]

i just made a mount block with a slot to put it through . hold in place with set screw

That's using your head.

 

[davidh]

cobalt drills work well with lube and pressure. . .

 

[jpfabricator]

Use a carbide tipped mason drill bit.

Sent from somewhere in East Texas by Jake Parker!

 

[kd4gij]

:+1: I use masonry bits on had steel all the time.

 

[Jeb1234]

OK, after a trip to Home Depot I picked up some Milwaukee cobalt drill bits.
50 rpm, heavy pressure and light cutting oil...got about 0.040" in before the bit dulled. Tried a second...no luck with cobalt.

Grabbed an old tungsten carbide tipped masonry bit, took a grinding wheel with a Dremel and dressed up the tip and tried it.
Same rpm, heavy pressure and cutting oil. Sounded like chewing on gravel, but it cut right through it with pretty little round holes.
This was definitely the hardest steel I've ever had to drill.

Thanks everyone. I now have a functioning quill DRO.