Thoughts on 1.0" Dia. HSS End Mill RPM?

Normally, I'm pretty good at estimating RPM rates... This one has me a bit worried that I might get it wrong.

The customer eventually will be using a 1.0" diameter HSS end mill to make a "hole" in aluminum - no coolant.

The surface finish is not critical, but making sure it at least works is.

The tool will enter the part at a 45 degree angle to the surface to make an "oval" hole if you will.

I'm thinking 400 RPM but would take any suggestions you may have.

The unit driving the tooling is about 150 lbs. total and has 3 HP so it's not a monster. It does, however produce up to 1000 lbs. of thrust so the tool shouldn't bounce around too badly. It's a thru hole for clearance on a big rig frame part so being "pretty" isn't as important as being long-term reliable.

Regards, Joe Agro, Jr. (800) 871-5022

01.908.542.0244 Automatic / Pneumatic Drills:
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V8013-R
Reply to
Joe AutoDrill
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Aluminum doesn't cut well dry in any condition. Especially with high speed. It will load up on the cutter and soon you will be cutting with the aluminum build up and not the cutter. Then it will get hot, gum up more ultimately break the end mill. Lubricity at the cutting edge is critical to avoid build up. Carbide allows a sharper edge and less porosity at the cutting edge for aluminum to build up. High speed and dry cutting aluminum will be a problem. There might be a honed edge carbide with or without some coating to provide lubricity in a dry condition. Check with some of your end mill suppliers. Good luck.

Reply to
Bill

It's tough to convince a customer who is running dry HSS drill tooling successfully that they will need some sort of lube when the process is semi-automated, running up at a 45 degree angle, and his drilling works fine. It's sold with an expectation of, "Hey, we need a different size collet for our new tooling" at this point because the educational process failed. He can probably use some type of lube stick or spray on the tool each retract, but at the moment, that is not in his plans and I can't convince him to do otherwise.

More than anything else, I'm curious what RPM would be close to appropriate for the process dry *if* it had to be done that way. My chart shows 750 RPM for HSS drilling so I figured around 400 RPM would be conservative and a safe place to start given the lack of lube and the different style tool being used in an interrupted plunge.

Regards, Joe Agro, Jr. (800) 871-5022

01.908.542.0244 Automatic / Pneumatic Drills:
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V8013-R
Reply to
Joe AutoDrill

They might be using an air blast on the tool. I used to cut big automotive prototype molds for grilles and IP clusters and we never used coolant and always roughed with HSS end mills - big ones. Great rooster tails of chips.

If they are using air, run the tool at 1000 RPM and feed it at .002 per tooth.

Reply to
John R. Carroll

I forgot something. Grind a rad on the tool. That will prevent build up at the tool tip and help the tool enter the cut.

Reply to
John R. Carroll

I think 400 is a safe RPM. Heat will be your determining factor. Right after it completes a hole and the spindle stops, grab the end mill, if it is warm your RPM is ok if it is too hot to touch, you RPM is too fast, or your feed is too slow, or your peck increment needs to decrease. What is the alloy and heat treat of the aluminum?

Reply to
Bill

The aluminum is most likely simple 6061.

I'll use a heat sensor rather than grabbing the tool. My calluses disappeared years ago when I stopped manual labor and became a slave to this keyboard and monitor! :)

Reply to
Joe AutoDrill

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