[simpits-tech] High speed steel drill

[simpits-tech@simpits.org]

kelly Mclaren wrote:
> 
> Thanks Steve, I'm drilling steel tubing, <finding the
>  speed of the edge of the bit in feet per minute at a given RPM >Now how do
> I calculate that?

It's easiest with a SFM chart, but it's just:

(Pi * bit dia. * RPM)/12

if I remember right. Somewhere I have a chart that makes it easy. First
find the bit diameter row and material column. Where the two intersect
is the spindle speed. I had a spreadsheet that I modified with the
specific spindle speeds I have available on the big drill press (wish it
had a quick change gearbox, but it's only a dual belt/3 pulley system)
so it was a piece of cake. I also printed it in color so that if the
material is drilled dry the RPM is black, cutting fluid is green, and
wax is red. I had pages for HSS, cobalt, bimetal (hole saws, mainly),
and carbide.

Unfortunately I can't find the bloody charts ANYWHERE.
AAAAAAAAHHHHHHH!!!!
-- 
Steve
mysticz28@swbell.net
Jesus saves, Budda enlightens, Cthulhu thinks you'll make a nice
sandwich.