"Pete C." wrote in message
ter.com...

Karl Townsend wrote:

On Fri, 8 Apr 2011 20:13:13 -0700, "PrecisionmachinisT"
wrote:


"Ignoramus30421" wrote in message
m...
Thanks to Pete C's advice, I am milling aluminum with HSS end mills.
These are Interstate end mills that Enco sells for $2.99 a piece.

I have to say that they work nicely, at 12 IPM, 2000 RPM, 2 flute,
1/4" diameter of end mill.

I am making those aluminum turner's cubes, which is a process that I
automated, so it takes me no time. All my friends want them.

Right now I am using depth of cut that is 1/3 of the end mill
diameter, and I am wondering if perhaps I am short changing
myself. Can I use depth of cut that is 1/2 of diameter? 1 diameter?
This process involves both slotting, as well as side milling.


http://www.archive.org/download/tuco...nsultant20.zip

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Nice calculator. I hadn't seen this before. The speed feed DOC are way
off the chart compared to what I do. I see it says up to .375 on a .25
EM. I'd be unlikely to try it on a full slot where you're cutting both
sides. But for $3, why not? No guts no glory. They may be assuming
high pressure flood coolant to keep the chips cleared. Something you
don't have.

I see the speed feed are both about 1/3 of what you are running. About
right on a small non production mill, IMHO.

Back to DOC. I've thought the ease of breaking an endmill must vary
with the square of diameter. Or put simply, a 1/16 breaks if you look
at it cross eyed, I only go maybe 10 thou or a fraction of a diameter.
AND only use it when nothing else will do. A 1/4 still breaks easily,
I'd be cautious at one diameter. Go up to 1/2 and you can cut real
deep - 2 diameters wouldn't cause fear.

I've not seen the above in calculators. So, its just one guy's
experience. It may be related to chip removal on my hobby quality
equipment.

Keep in mind, I'm not like Pete. I've broke a lot of end mills.

Karl

There are a lot of variables that all interact, I haven't had a chance
to look at the calculator noted, but I expect there are some high end
packages that take all variables into account.

Some thoughts:

- The length of cut, i.e. the amount of material the end mill flute will
sweep through determines the chip size and needs to fit in the available
clearance of the end mill. For slotting the length of cut is the full
dia of the end mill.

- The depth of cut, i.e. how deep the end mill is cutting in the
material on each pass is a function of the length of cut and the
rigidity of the end mill.

If you are slotting, i.e. cutting the full diameter of the end mill, the
dept of the cut is going to be limited by the lesser of machine HP or
end mill rigidity, and to a limited extent the ability of the coolant to
flush the chips out of the way. Recommendation, start testing with a
shallow depth of cut and progressively work to deeper cuts while
monitoring until you can tell that it's starting to stress things, then
back off a bit and use that as your depth of cut.

If you are side milling, the shorter the length of cut (step over), the
longer the depth of cut (step down) you will be able to get away with.

The calculator allows user input of depth /dia. ratio and adjusts the sfm
and chipload output so as to compensate for transverse rupture.

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