On 11/11/2014 11:00 PM, Stuart Wheaton wrote:
Drilling into the end of a large threaded rod, centered, punched and
drilled starting at 1/8" worked up to 3/8". 3/8" is about 1/4 of the
way into the hole and quit cutting, Either I hit a hard spot in the
steel, or it got work hardened, I was using coolant, but not flood.

Swapped to a new and sharp HSS bit, no joy at all.

Suggestions?

I can:

1. Try a masonry bit, 3/8 is something I have in the shop.
2. Heat it with a plumbers torch and see if I can temper the hole.
3. Go get a TiN or Cobalt bit...

I need to finish the 3/8 and then drill it to 13/32nds, then tap, so I'm
close, but I'm worried about the tap and the hard spot too.

Any help would be great!

Stuart

Picked up a TiN bit in the AM, Filled hole with coolant, fired up the
drill press (which is what I did the original drilling in) and it cut
through the hard spot. Final drill and tap went without incident.

Material was a large threaded rod, about 1.25" diameter, likely metric
since we are fixing an English company's goofs, sourced from McMaster,
good quality, red ends, not stainless. I would say that the guy
ordering can be trusted to order good stuff, but then he only got me a
bottom tap, so I guess I can't say that.

Stuart