Another question about TIN coating

[tbaker2500]

I'm sure this has been answered many times. Unfortunately, my google-fu hasn't turned up the answer yet. So sorry in advance. :-)

I'm new to coated end mills, I've been using uncoated up til now. I'm starting to do some production work with my small Tormach 1100, and I was looking into coating. I'm cutting in 6061 T6, 1/2" 2 flute Atrax carbide end mill, doing a 1/4" depth of cut pocket at 27ipm, 4500rpm.

I tried a TIN coated carbide, getting mixed messages about wether it helps in aluminum or not. Within the first few minutes of cutting, I noticed that the distinctive gold coloring looked to be worn off the end mill around the cutting surfaces. Now, it could be one of two things to my eye.
1. The TIN coating wore off almost immediately, and therefore why pay extra dollars. Or,
2. The aluminum was wiping a coating on top of the TIN coat, which doesn't seem to good either.

Any help in understanding how, or if, this coating is useful in 6061 would be much appreciated.
Tom

[doorknob]

My experience with TiN-coated drill bits in aluminum has been that they don't work well because the aluminum sticks to the coating.

[djr76]

I dont think the Tin wore off, its probably aluminum smeared onto the cutter making it appear to have worn off. I use uncoated tools for aluminum.

[tbaker2500]

I looked much closer today, comparing my uncoated with this coated, and I do think it's smeared aluminum. Is this common, or am I cutting wrong?

[keebler303]

Its common, TiN is not good for aluminum for this very reason. Stick with uncoated carbide.

Matt

[RICHARD ZASTROW]

Could be a number of things. Coated tools often have honed or radiused edges. Aluminum likes sharp edges. Some coatings do not get along well with some coolants. Dry cutting usually requires high surface speed to get beyond the point where aluminum welds itself to the cutter.

Dick Z

[tbaker2500]

As a follow-up, the bit in question actually has cleaned itself, more gold coming back, which proves it was aluminum. Still the same flood coolant, but I was doing less heavy cutting.
Thanks for the advice!

[MCImes]

If you're doing real production volume why not use an EM designed for Aluminum? Like a 3 flute ZrN coated (or uncoated). You should be able to go a lot faster than 27 ipm with the right cutter. TiN has a relatively high coefficient of friction compared to other coatings leading to more welding/cutter loading so its not a good choice for Al.

So, use uncoated, ZrN coating or there's one more that im blanking on that is designed for Al. look it up if you're curious

[tbaker2500]

Consider this hobby production work, because REAL production work would require a machine with a lot more that a 1.5hp motor. I'm using a Tormach PCNC1100. :-)