"Bob La Londe" wrote in message
news
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.

Does it have parabolic flutes?