Re: [CAD_CAM_EDM_DRO] feeds and speeds.

dave engvall wrote:

> I hate to clutter up the bandwidth but need help
> with feeds and speeds for .5" HSS or Cobalt
> roughers.
> With and without coolant.
>
> The mill is a BP I equivalent except for heavier
> tool holders.
>
> Thanks in advance.

It depends entirely on the materials (as you've already
spec'd the cutter. For aluminum alloy, 600 FPM is recommended,
which comes out to about 4250 RPM. (Seems a little high
to me!) For mild steel, 80-120 FPM is recommended,
which comes out to about 800 RPM.

Now, for feed rate, you take the RPM, multiply by number
of cutting teeth, and multiply by the number of thousandths
of an inch per tooth, and you get the feed rate in IPM.
So, for a 4 flute end mill at 4000 RPM, and a chip load of
.001", you get 4 IPM.

Now, what is a good chip load for a .5" end mill? .0015"
is good for finishing, and you may be able to go up to
.010" in soft materials with small depth of cut. For full
width plowing a slot at sizable depth, you will have to
reduce the chip load.

So, a lot depends on the rake, coating, sharpness and
other features of the end mill itself, the rigidity of the machine,
workpiece itself, and the workholding. If everything is
very rigid, you can really plow in with the Cobalt roughing
cutters, up to the power limit of the machine.

For instance, a 2 Hp machine can remove 6 cu. In. / min
of aluminum alloy, but only 1.2 Cu. In. of mild steel / min.

All of this comes from a McDonnell-Douglas 'Speed and
Feed Calculator' I found at a local scrap yard, but they
seem to be right on.

Jon