SINGING END MILL

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BROCKWOOD

H-M Supporter - Gold Member
H-M Supporter Gold Member
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May 26, 2017
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I's a 5/8" 4 flute end mill that happens to be old American & very sharp. It performs much better than the ones I got from Grizzly. Now, I admit that with this mini mill I usually take cuts that would be the equivalent of a skim coat. But, this end mill has impressed me, so I tried a deeper cut - say 0.010ish without incident. I was doing pretty good at twice that depth of cut when it started 'singing'. I slowed the cutter speed & the resonance became a rumble. By raising the speed & hand feeding, the pass was complete. I have 3/4 total to mill out. Any suggestions? The piece being cut is A36.

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I think that the machine is the limiting factor; generally, slowing the cutting speed will control chatter. With a more rigid machine, !/8" or more would be possible, even double or more, especially with coolant.
 
I second John: I would say the machine is not rigid enough to use a 5/8" endmill in steel.
-Mark
 
Thanks guys! I'll just have to suffer through with smaller cuts then. It took forever to finish the dovetail. Slow but sure it is then.
 

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You might try locking down all the axes that are not supposed to be moving to see if one (or more) of them is the cluprit leading to unstiffness.
 
My son gave me a saying for this, "feed the bird". More feed will get rid of the vibration. Now if your mill won't take that, also reduce your DOC.
 
3/4" end mills on a mini mill is outside the work envelope of the mini mill unfortunately. I use one all the time, but don't expect to make deep cuts. Tighten all gibs as much as you can. Lock the Z axis and X axis or Y axis down tight. keep the stick out of the end mill to a minimum from the collet. I usually don't make more than .010 - .020 cuts on steel since the mini mill just doesn't have the rigidity for more. I usually run about 50 sfm for steel with that large an end mill. I think A36 is code for whatever we can find in the trash basket, it usually does not get a nice finish on the mini mill. I use cutting oil. The sharper the end mill the better. I also use a 2" 4 flute insert face mill for finishing, but it is limited to .005" depth and I run it at 400 - 600 rpm. I use APKT1604PDFR-MA3 H01 milling Carbide inserts for aluminum, copper on all metals for the face mill. These inserts look like they are chromed and produce a very nice finish on soft metals(almost a mirror finish) and on very light cuts on steel the finish is orders of magnitude better than and end mill. One again due to the limited rigidity the depth of cut must be very shallow. Those inserts are very sharp compared to standard carbide inserts so they are easy to chip. I also use them in a 1" face mill. Standard carbide inserts leave a mess on steel with the mini mill.

Just my opinion.

Roy
 
So, I did make a video. File size was just over the limit, so would not upload here. I put it on Facebook:
https://www.facebook.com/video.php?v=1422367537971242

For those that don't do FB, here is pic of my slow n steady progress.

A36 code for scrap LOL I like that! I bought a 2' chunk of it. It didn't feel like scrap pricing at all. Maybe $50~!

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Be worth you trying a roughing end mill, you should have a much easier time hogging out features like that, particularly if you're struggling a little with rigidity. Saves wear on your standard cutters so they're sharp for nice finish passes too.
 
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