Diagnosing issue with carbide end mill buildup with aluminum

pfisher · Oct 21, 2017

Very new at this stuff, and I would appreciate some confirmation that I understand the problem I am having with the following:

1/2" bright carbide 3 flute end mill cutting what is likely 6061 aluminum. Running this on a heavy manual vertical mill at 3000 rpm with not a very wide cut across the side of this pice. I am getting buildup on the relief of the cutter flutes and "squishing" on the end of the workpiece.

Doing a little research today and I believe this is because I ran this with no coolant or air, with the main problem being chip evacuation. Is that the right idea, or is there something else I am doing wrong?

--
paul

Limy Sami · Oct 21, 2017

Yup you need coolant, .not only to cool and lube the tool but to flush the chips away.

Finegrain · Oct 21, 2017

Squirt a little WD-40 on the cut next time. Works great for cutting Al.

Regards.

Mike

Milland · Oct 21, 2017

Another thing that can cause this is worn spindle bearings or non-concentric holding of the tool. What happens is either loose spindle bearings or eccentric spinning allow the flanks of the cutting edges to contact the aluminum, and as they rub they generate heat that leads to a transfer of metal that then accelerates welding (small bits rub, weld more bits, etc.).

Check for loose bearings with a test indicator, push spindle while contact of indicator is against the nose. If you see more than a thousandth or so of motion you may have an issue there. For eccentric tooling, spin (by hand) tool edges against indicator needle (just a tiny bit of loading on the needle, ~.005" or so), see if edge displacements vary by more than .001".

garyhlucas · Oct 21, 2017

Toss the cutter in some Lye, Caustic, Sodium Hydroxide, different names for the same thing. Aluminum will be gone and no damage to the tool.

Mike C. · Oct 21, 2017

As said, a shot of WD-40 will do wonders for the cutter and the finish.

Bobw · Oct 21, 2017

You have aluminum buildup on the OUTSIDE edge of the tool...

If you are having a standard melt down problem (too much heat) or a
chip clearing problem, or any normal dry aluminum problem, you would
have buildup/clogged flutes...

2 possibilities, you are spinning the endmill backwards, or you are feeding
somewhere around ZERO Inches Per Minute.

What kind of feed rate are you using? I know its a manual mill, that makes you the
controller.. Do the math, and One Mississippi, Two Mississippi it out...

So lets say you want to take .010 per rev, about a minimum if you are taking a moderate
width(.100") full depth cut on the outside of a plate or part... 3000 rpms times .010 per
rev is 30ipm.. If your cranks are .200 per rev, you need to crank that puppy at a clip of
60 rpms, 1 rev per second.

I'm guessing you weren't turning the handle that fast.

pfisher · Oct 21, 2017

Bobw,

Thank you, this has certainly given me something to consider.

This was the first time that I was using this machine and did just assume that it was spinning forward. Thinking about the way that it was "cutting" that would explain why a brand new end mill would not make good chips and seem to smear around the material. Never even considered that was what was happening.

Assuming that it isn't that. I was certainly not cranking nearly that fast on the feed. It was at most one revolution every 2-3 seconds. I'll lower it to 2000 rpm and see if I can get the right feed turning it manually.

Lakeside53 · Oct 21, 2017

Lowering it to 2000rpm isn't going to do squat unless you also lubricate it. Kerosene or WD40... little Squirt every few seconds.

pfisher · Oct 21, 2017

Lakeside53, have already packed the WD40!

Lakeside53 · Oct 21, 2017

I buy it by the gallon and load it into a squirt bottle; far better than a spray can. In any case have plenty of ventilation - you breathe the fog.

pfisher · Oct 21, 2017

I think I may have actually ended up doing what Bobw suggested and running the spindle in reverse. The machine is an older Lagun mill with low and high gear. I switched it from low to high gear, but changed nothing else. Googling about seems to indicate that switching between low and high gear will reverse the direction of the spindle. Can anyone confirm this would be the case?

NodecoMachine · Oct 21, 2017

Just watch the spindle when you turn it on

Mike C. · Oct 21, 2017

Yes, on a typical Bridgeport type head with backgears, rotation is reversed when backgear is taken in or out. My opinion that the switch should never be labeled fwd/rev, because it's going to be wrong 1/2 the time. When I started working at the chrome shop, one of the guys said I had "fixed" the mill because it was running in the right direction in backgear... They also had no idea how to get the belt drive lathe into backgear.

HuFlungDung · Oct 21, 2017

Bobw said:
2 possibilities, you are spinning the endmill backwards, or you are feeding
somewhere around ZERO Inches Per Minute.

Eagle eye!

Actually, zero inches per minute is the correct feed when running in reverse. Here I'm always giving the newbies shit for underfeeding, but not this guy

guest · Oct 22, 2017

I got a good deal on a vert. band saw a couple years ago, I guess the owner didn't like the way it cut.

It works pretty good after I turned the blade around so the teeth were pointing down.

Larry Dickman · Oct 22, 2017

In addition to all the above, you say it's "Likely 6061"

If your trying to cut 6063, or any H series, 3003, 5052, this is about all you can expect.

Lakeside53 · Oct 22, 2017

I cut those all the time. While some are gummier than others, all cut just fine with the lubricant or the correct coolant application.

metlcutr55 · Oct 22, 2017

I find a brush puts on enough wd40 or light oil etc, and saves a mess. also, if the alum has stuck to the cutter once, it is much more likely to stick to that same cutter than before if used again.

DMF_TomB · Oct 22, 2017

pfisher said:
Very new at this stuff, and I would appreciate some confirmation that I understand the problem I am having with the following:

View attachment 210815

1/2" bright carbide 3 flute end mill cutting what is likely 6061 aluminum. Running this on a heavy manual vertical mill at 3000 rpm with not a very wide cut across the side of this pice. I am getting buildup on the relief of the cutter flutes and "squishing" on the end of the workpiece.

Doing a little research today and I believe this is because I ran this with no coolant or air, with the main problem being chip evacuation. Is that the right idea, or is there something else I am doing wrong?

--
paul

.
quite normal cutting aluminum dry to get it sticking to flutes. a little oil or flood coolant will really help reduce sticking to flutes
.
actually kind of a tradition when apprentice clogs up end mill really bad for old timer to laugh his ass off at the new guy. some metals like aluminum stick really easy and you cannot ignore it
.
not saying you cannot cut aluminum dry but you really have to watch the heat build up, edges dulling and it will start sticking and often in as little as 30 seconds the flutes so full of stuck on aluminum to get part movement and to scrap the part from the mess made
.
it helps to use a end mill made for aluminum. they are extra sharp, and made to stick less. general purpose will always give a problem cutting dry

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