cavelamb wrote:
John R. Carroll wrote:
Karl Townsend wrote:
It depends on the material Karl not the rating as a bolt.
Carbon steel and Stainless are both avaliable in grade 8.
Its a steel bolt.

Then you'll be good with a HSS Split point drill at 40 SFM and oil
for a lubricant.
Keep a good bite on your drill but it won't work harden and peck
often as you refresh the cutting oil.



The real difficulty is breaking through the far side.
Snug up the Z axis clamp a little and pay attention.
LOL



Got a trick to keep from breaking bits on the back side?

Squeezing my butt cheeks together didn't seem to help, not the drill anyway.
Snugging the Z at the end will keep the drill from grabbing and that's the
problem.
On a manual machine, the spindle will release any slop or backlash as you
break through and drills turn into wood screws in a hurry.

I saw a guy rapid a drill an inch or more into an aluminum part once and
when the spindle came up, the drill stayed - unbroken - in the job.Ruined
the collet.
The part was a mold cavity so somebody had to figure out how to get the
thing out.
I'm glad that guy wasn't me.
The thing I've wondered about since is where the aluminum went?
The drill and the stock couldn't have occupied the same space but it sure
looked that way.
LMAO

--
John R. Carroll