[scoperoller]

I have a new Sherline 5400 CNC mill. I have written gCode to mill away a section of aluminum from the workpiece, but the limits of what it canb remove are so low that either these Sherlines are just toys, or I am doing something wrong. I am using a 1/4" finish end mill, and it stops if I try to remove 0.01" of 6061 aluminum, attacking it from the edge. Yes, it is oiled. It can cut 0.03" of acetal without trouble, but not being able to cut aluminum (except in .0005" slices) makes this pretty much useless except for learning what I need before buying a REAL CNC mill.

[awerby]

Your Sherline is a real mill, but it's small. It should be able to deal with a .01" DOC cut in aluminum, but not all at once. With any mill, you generally take no more than 1/3 of the tool's diameter in a single pass, so the first cut would be about .083 from the edge. Also, you're probably going to be better off with a roughing endmill, or at least a 2-flute endmill, rather than one intended for a finish cut. What's your spindle RPM? How fast are you feeding? Did you use a speeds/feeds calculator, or are you just trying stuff to see what works? When it stops, does the motor stall, or does it keep spinning but the belt doesn't move? Is your aluminum heat-treated, or soft? Hardened aluminum actually cuts a lot better than soft, because soft aluminum is gummy, which tends to catch the tips of the flutes instead of shearing away cleanly.

[scoperoller]

The motor stalls. I will try a roughing end mill. I have been trying half diameter. I guess that's too much.

[scoperoller]

I tried using a 3/8" roughing end mill and the results wre only a little better. Sherline Tech Support says trying to remove 3" x 0.01" of aluminum is something even a Bridgeport can't do. This doesn't sound right.

[awerby]

I'm not sure what you told the tech, but the Sherline can do that - and so can a Bridgeport. Neither can do the whole 3" swath at a time, though. A 3/8" cutter takes a lot more torque to cut with than a 1/4" one, though, and I wouldn't recommend it for this. Try a 2-flute endmill, preferably a "bullnose" with radiused corners that will have less tendency to hang up in the cut. Keep the RPMs up in the sweet spot for your spindle motor; the variable speed motor the Sherline uses doesn't have as much torque in the low range as a comparable fixed-speed motor stepped down with pulleys. And feed fairly slowly, like about 3" per minute.

[CosmosK]

My first mill was a Sherline. It was good for softer stuff, but AL was always difficult. Mostly the deflection of the machine would be my issue. You need to take light cuts. However, .010" with a .250 end mill doesn't seem excessive.. that sounds light. What feed rate and RPM are you using? Is it 6061? Is it anodized? A Bridgeport can easily take .010" with a face mill all at once. I've done it many times.

[scoperoller]

Thanks for all the help. I switched to a 3/8" roughing mill, 5 in/min., 0.02" at a time, and ever\ything works.

[ttnt77]

this is not easy to get answer