Arrhhhhghgh!!!!! I am at the end of my rope!

[CoolHand]

I am cutting channels in 6061 T-6 aluminum, .31" deep with a 1/4" carbide EM. Its a two flute Niagra, solid micro-grain, 45 deg helix, .375" LOC, TiCN coated.

I'm spinning it at 5000 rpm (max for this machine), and feeding it at 30 ipm, with a DOC of .075"

The last EM I had was uncoated, and it got a builtup edge, clogged the flutes, and broke. No problem, switched to the coated Niagras, reduced the DOC, and tried it again. This time, I literally shelled it. Peeled the flutes right off the central spur, now I have a pointed engraving bit.

What gives here? I was pushing the uncoated mill at .004" per tooth, but I broke it. So I stepped the feed down to .003" per tooth.

I was cutting dry.

There was no alum stuck to this Niagra cutter.

I am at a loss here.

I've broken about $80 worth of mills on this job, and its really pinching my profit margin.

Somebody please help me here.

I'm doing everything they say to do with carbide and aluminum, and all I've got to show for it is a pile of junk cutters.

Arrrrrrghghghe!!!!!!!!!

[Rekd]

Put some coolant on it, or run it up faster to try and generate some heat. Just a guess, but I'd try .05 DOC at 50ish IPM with a mister on it.

'Rekd

[CoolHand]

OK, I forgot some things.

I don't have a mister.

I've cut 16 of these parts (in a row) with one endmill (uncoated carbide no name). I was running it at 40 ipm with a .125" DOC.

Then all of the sudden, that mill broke. And the other one I had just like it lasted like 30 sec, and then another 30 deg helix EM lasted about 3 sec. So I ordered some coated Niagras with half the LOC so they would be stiffer. This one cut like a champ, and then just exploded. Not a sound, until it broke. Perfect surface finish, then boom.

I don't understand what is happening here.

I tried doing the same thing that worked for all those parts in a row, except now it only ends with exploded endmills.

What has changed?

Why won't that work now?

This is insane, I am contemlating giving up machine work, and buying a pottery wheel.


Somebody stop me!!!!

[Rekd]

You prolly got lucky on that first EM.

'Rekd

[CAMmando]

Is a channel in a larger part, or are you actually cutting a part that ends up looking like a channel ?

How is the work piece being held ?

Not to ask a stupid question, but after one endmill broke, are you cutting a fresh part or the same part?

What kind of tool holder are you using ? If a collet have you checked for runout ?

[HuFlungDung]

Coolhand, get a mist unit, it will likely cost the same as a pottery wheel, but you're already set up for machining, so what the heck

Lacking a mist unit, I would apply an air blast, and paint the surface with heavy cutting oil (so it won't blow off), in an attempt to get a little bit of lube on the cutter

[CoolHand]

OK, I started fresh with a new billet after the first two ate themselves.

My machine has a BT-40 taper spindle, and I am using a solid set screw EM holder less than .0002" TIR at the tip. Spindle bearings are solid and smooth.

I have a flood coolant system on this machine. The basin is currently filled with a water soluable lard oil mixed about 30:1

I can fortify that solution if it needs more lubricating power.

Here is what I am thinking of doing:

Reducing DOC to .050", increasing feed to 50 ipm (that's .005" ipt), and turning the hose on it (flood coolant).

At this point I don't even care if the EM wears out before it should, as that would indicate that I have kept one in a single piece long enought to wear it out.

Let me know if that is way out in left field.

Also, the reason I am resisting the mister is because my air compressor can barely supply enough air to keep the tool changer on my machine running, much less a constant bleed like a mister. I can buy a lot of $20 EMs for what a bigger/another air compressor will cost.

Thanks for your help guys.

[CoolHand]

Opps.

BTW, here is a pic of the parts I am cutting.

Click Here to view the Bane of all 1/4" EndMills

Its the pic in the middle (or the only one on the page, depending on how you want to look at it.)

Thanks again guys.

[HuFlungDung]

Have you tried M3 instead of M4?

Seriously though, I would decrease the feed. What you are using is pretty heavy for that small of a cutter when it is completely engaged in the cut. The chip is likely a bit too heavy and wants to slip shear, which makes it pile up and seem thicker than it really is.

Cut deeper at a slower feedrate, maybe 10 to 15 ipm at .125" deep

[CoolHand]

Originally posted by HuFlungDung Have you tried M3 instead of M4? . . . . . .

That's not funny.

I'm stupid . . . . but not that stupid.

Anyway, which way should I do this?

Thin DOC, fast feed

OR

Deep DOC, slow feed

I'm conflicted.

I would like to stay with the option that heats the workpiece the least. I also want to make the most efficiect use of the machine's time.

[Rekd]

You're in a catch 22, Ryan. The tailn coatings require heat to work. Heat is not a bad thing so long as you can remove it quickly, either via coolant or taking it out with the chips. (The latter method is harder to achieve in certain situations)

'Rekd teh Trial and Error is too a science!!

[HuFlungDung]

I would try a lighter feedrate, whatever depth is up to you experiment with. When guys are milling at high feedrates with a small cutter, it is usually not fully engaged in the cut.

I don't know if lard oil is good for aluminum or not. WD40 works good but it is stinky to be around.