I've drilled High grade HSS+Colbolt+MM. With a solid carbide drill.
It was Mo-Max cutter. I was making a forming bit for my metal lathe.

The trick is to have a solid and firm hold. Drill press.
Drive the drill in with firm pressure and when the drill gets
red hot - and the spot on the metal does - the drill goes through
it nicely. I left the drill in the chuck afterwards - I didn't
want to shatter it nor melt something.

It was a 1/8" drill. Carbide comes in all sizes.

Martin

On 1/31/2013 9:35 AM, PrecisionmachinisT wrote:
"John B." wrote in message
...
On Wed, 30 Jan 2013 23:56:43 -0800 (PST), wrote:

On Saturday, July 15, 2006 7:07:29 AM UTC+5, Ignoramus19864 wrote:
Are grade 8 bolts drillable? I just realized that bolts that I bought
from McMaster this afternoon for making fittings are grade 8, high
strength, and am a little worried that perhaps they are going to be
difficult to drill (lengthwise).


I believe that Grade 8 fasteners are in the RC 33 range. You should be

That's minimum, 39 is max.

able to drill them with normal high speed drills.
It might be advisable to look up the proper cutting speed and not
exceed it :-)

I probably would proceed as if it were 4130 at 39 Rc


--
Cheers,

John B.