On 12/23/2017 7:50 PM, Bob La Londe wrote:
I've been roaching out and regrinding twist drills all afternoon. I do
a typical 3 facet grind on each cutting edge and then thin the web.
Works for most things. In stainless it produces long stringy chips. So
I didn't have to stop every time I roached a bit I gather up 4 that were
the right size and set them on my tool cart. When I got to one from
Precision Twist Drill it drilled about the same as the others, but the
chips came out in little pieces, Almost a turning insert with a chip
breaker. It might have even take a little less force. Was that a fluke
or is there a different grind that works better in stainless? Of
course, I paused to long on a peck and roached the tip so I had to
regrind it. Amazingly with my regular 3 facet grind the tip has been
outlasting the other bits including my Chicago Latrobe about 3 to 1.

I've been drilling fairly deep holes (2.75inches) in 304 with either an
F drill or a 6.5mm drill for the last couple hours making last minute
Christmas presents.


Holy Crap! I never did figure out how it was producing chips instead of
strings, but after I resharpened the Precision Twist Drill it finished
all the rest of my deep drilling without being resharpened one time. It
seemed to grind easily enough, but man it sure is tough in operation. I
hate to spend the money, but it would be awfully tempting to replace all
my drill sets with these. When I said 3:1 yesterday it was just how
many more holes I had drilled with it over previous resharpened bits
when I called it a day. We are talking atleast 5:1, and it just barely
starting to show signs of edge wear in the chips. I could probably
punch several more holes with it.