On Tue, 2009-11-10 at 22:07 -0700, David Braley wrote:
>
> Gene Heskett wrote:
> > Greetings;
> >
> > One of the things I have not yet learned is how to get the most swarf from
> > a
> > given milling tool. I have a tendency to go slow, so the swarf is
> > sometimes
> > so thin it settles like snow flakes when it is blown away from the work.
> >
> > Obviously this is wasting the cutting edge of the tool, dulling it
> > prematurely.
> >
> > So when my fresh shipment of 1/8" mills gets here, I would like to be able
> > to
> > have it throw thicker chips and far fewer of them but remove lots more
> > metal
> > before they dull.
> >
> > I'm going to rig me an oil squirter from an in tank auto fuel pump to try
> > and
> > keep the mill wet. With a tuna can under the workpiece I can catch most of
> > the runoff, and maybe even filter & recycle it. Details to be invented yet
> > in the finest of shade tree mechanic methods of course. ;)
> >
> > Assuming I keep the area wet with cutting oil at a high enough flow that I
> > don't wind up with a muddy slurry, but do have enough chips to act as a
> > wick
> > and keep the mill wet from the cutting oil they absorb (or the oil level in
> > the tuna can is high enough), and the 1/8" 2 flute carbide upcut spiral
> > mill
> > is turning 2500 rpms, how fast can I feed it while doing a 0.020" deep cut
> > per pass without breaking it? Slower and deeper, or shallower and faster
> > for
> > best tool life?
> >
> >
> Feeds and speeds as you already know is a delicate dance with what
> material you're machining, spindle speed, number of flutes on your
> milling cutter, table speeds and lubrication. And like you discovered
> above, it's better to cut than rub your material off.
>
> It sounds like you are running a smaller machine. If that's the case,
> another factor comes into the equation and that's how stable or rigid
> your spindle is. A spindle that is built with bearings less than ABEC
> 7's is not going to give you the rigidity you will need for long tool
> life. Your small spindle my wind way up, but that'll be useless when you
> start to load it with heavier cutting. Procession is not your friend.
> Even if it's so small, you can hardly detect it.
>
> I like your oil squirter idea for lubricating your cutter, but I want
> you to consider instead using a spray mister. The reason is simply
> because once you start to make bigger chips with those tiny cutters,
> you're going to have a problem with getting them out of the way. The
> smaller cutters are more commonly broken because the chips clog up the
> works. A spray mister will by its nature, blow everything out of the
> slot you're cutting, keeping the system cool, lubed and clean. It's less
> of an issue with larger cutters. The mister does make more of a mess,
> but with simple and carefully placed shielding, you can contain most of
> it. You will also be surprised at how little mist coolant you'll end up
> using when you get it adjusted right.
>
> My worthless two cents. ;-)
>
> David
Cutting Al is absolutely a can of worms.
Rule #1 is to use T6 if possible.
#2 is to remove chips so they don't recut. Sometime a shop vac
works well here.
#3 even a bit of kerosene or WD-40 helps at times but the surface
tension may glob up the chips and make a mess.
#4 air and shop vac may do the best job.
If you get the Al to high temps it flows and bonds to the cutter. I once
saw a cutter at Boeing Surplus: probably 1 to 1.5 inch dia and 8" long
with a cone of melted Al on it. Going for cheap if one had a 50 taper
machine to use it on. A couple of pounds of lye would have done a good
job of cleaning it up (and made a decent amount of hydrogen). :-)
Even the experienced guys have problems. ;-)
It has been my experience that carbide mills don't do well on flexible
(wimpy) spindles. HSS is much tougher and you just live with the slower
speeds.
Most extruded Al is way too soft to cut cleanly and leads to problems.
Plunge milling to remove material is probably the best approach, just
watch the tip of the mill for fusion of base material.
Naturally YMMV.
I'd rather deal with P20 (Rc 30 4140) than Al.
HTH
Dave
>
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