"Bob La Londe" wrote in message
...
What is the "old knowledge" about interrupted turning. I've been
doing some Google searches, and checking the videos on YouTube, but
most results seem to indicate a need for new high tech special
inserts. Or more accurately be aimed at selling such inserts and
insert tools.
I don't have to do it often, so I don't mind if it takes a while or
if I have to push it a little bit, but I'd kinda like to know how to
do it the "most effectively" with teh tools I have.
I've got a Precision Mathews PM1440-LB 14 x 40 lathe that claims a
3HP motor. So far this lathe does a pretty good job, but I'd like
to shy away from maxing out the motor if possible. Feed per rev is
pretty flexible, and its got spindle speeds from 70 upto 1255. Its
more rigid than the average Chicom lathe, but its still a Chicom
lathe so I'd also like to shy away from pounding on it to hard.
I've got a few 1/2" x 4" HSS Cobalt bits. I could sacrifice one to
this with no qualms.
How you would you do it if you were going to hand grind an HSS
insert for the job?
P.S. For why guys no tell me about vertical shears. That's an
sweome grind for getting a smooth/er finish.
The first HSS bit I grab for quick jobs in aluminum, brass, mild and
harder steel and stainless is ground like a threading tool, but closer
to 90 degrees than 60 so the point holds up longer. The cutting edge
slants downhill toward the point as a result of freehand grinding, not
intent, but it's handy to remove the nub left on the stock from a
cutoff bit and not too sensitive to being a little off center height,
and quick to resharpen. It stood up to turning stainless squares into
circles for the races of a solar panel thrust bearing.
I don't think it's the ideal shape for any particular task but it
adapts well enough to a range of them. I originally ground it to turn
down straight pilot sections on stainless screws for my antenna. The
root-diameter pilots align inner and outer holes in telescoping mast
joints.
I should mention that I use Multifix tool holders that rotate in 9
degree steps, which is very convenient to compensate for the imprecise
angles of hand-ground bits. The Aloris system has a better selection
of insert toolholders.
http://www.lathes.co.uk/multifix/
--jsw