On Sun, 21 Apr 2019 at 03:34, John Dammeyer <[email protected]> wrote:
I used the Machinist toolbox to figure out what sort of speed and feed I needed
but ended up running the mill faster (thought I'd read it should be 3000 but it
was supposed to be 2000). Typo error.
OK. So tool bit 0.09375. Two flutes. HSS. Chip load 0.00551. Aluminium bar.
SFM set at 40 which called for 2000 RPM and about 22 ipm
.094 tool at 2000 RPM is 50 SFPM, really slow for aluminum.
600 SFPM is recommended.
chip load for HSS end mills should be .010 * end mill
diameter, so .010 * .094 = about .001".
At these settings, feed rate should be 4 IPM.
I have stopped using all HSS in the smaller sizes, I buy
10-packs of 1/8" solid carbide end mills for about $3 each,
and they last a LONG time. Crummy "HSS" tools from China
last about 5 minutes before dulling begins to show.
Name-brand M42 HSS tools seem to last at least 3 times
longer, maybe even up to 10 X better. And, they rarely cost
more than $1 extra over plain HSS.
One of the tricks with aluminum is to keep the cutter
moving. So, take a shallow cut and keep the feedrate up,
and always do climb milling if possible. Higher feeds keep
the heat from being concentrated in one spot on the workpiece.
Using a 1/8" carbide end mill at about 3000 RPM (limit of my
mill), I would plow full-width cuts at a depth of .062"
(half diameter) at about 4 IPM, then cut the sides at 10-15
IPM with a side step over of about 0.25 - .050, and a final
dimension pass taking off .010 on the side at 8 - 12 IPM.
This is with a 4-flute cutter. As long as you keep the
cutter moving right along, you won't have a problem with
gumming up the cutter.
And, flood coolant REALLY helps with the heating problem. I
have a throttle valve on my coolant system, and use the
smallest LocLine nozzle, and throttle it down to a little
jet pointed right at the cutter. So, it just spreads out a
little puddle on the top of the part.
Jon
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