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By ndlsjk

February 28, 2018, 2:05 pm

Regarding high speed toolpaths and coolant

Hello Eldar,

I've been running faster and harder every day with HSMA and wanted to pick your brain for a minute regarding a set of parts I ran a couple days ago.

The material is A2 Tool Steel 230HB, big solid chunk held very securely so I can go like a stabbed rat.

I was cutting using a .360 4FL Var Helix AlTiN Coated End Mill (no corner radius) that was .875 LOC and sticking out 1 inch.

I've been experimenting with going to slightly lower WOC to take advantage of HSM and chip thinning operations. I was at 10% (.036) WOC and .750 DOC cutting at 7334RPM and 106IPM. This was insane fast, and the cutter made it through 3 slots that were 3.5x2.0 with life to spare.

The problem came with HEAT building up in the part. The first one I cut dry, the chips were blue and had nice crisp edges under the microscope. The part, however, got VERY hot to the touch, to the point that there were a few marks left after a 0.005 finish pass (it didn't move in vise, so must be heat expansion?). I ran the next 2 with coolant and they cut fine, however I wasn't letting the AlTiN get up to temp.

Would the proper solution be to go back to the heavier WOC with lower speeds and feeds to get a heavy chip to take more heat? This seems correct, but I am kind of addicted to the speed now.

Sorry if this is outside the scope of the forum here, but I figured it'd be an interesting discussion to have with you. I appreciate your time and effort as always. :ernaehrung004:


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Eldar Gerfanov (Admin)

March 1, 2018, 8:14 am


The reason the part is heating up is friction.

When using HSM machining it is VERY recommenced to also turn on Chip Thinning.
Since you said you run at 100 ipm i figured you had Chip Thinning off.
Otherwise your feed rate would be 179 ipm.

Please check the screenshot.
With Chip Thinning enabled you get much better tool life and much better productivity.

At the same time your part will be much cooler.

For HSM Machining I recommend using air blast to cool the part and clear the chips.

Best regards!

Capture_45878695.PNG Capture_45878695.PNG


March 4, 2018, 12:13 pm

I see my issues, and it brings me to another question:

I did have HSM and Chip Thinning enabled, I figure the 2 are prettttty much always used together, however I had 2 differences from your screenshot.

I always set my endmills as "Solid End Mill" rather than "HP/Roughing End Mill" as I was under the assumption that was referring to the serrated style roughing end mills that I do not use.

The other issue would be the "Tool torque" maxed @ 70%. I've been hesitant to crank that up but I see if I am using the HSM/Chip thinning choices I should set that to about 150% and get ready for some serious pucker factor :tongue:

Would you consider any tool with variable flute geometry "HP" or is there some other criteria?

I'm actually tossing around buying the air blast for my VF-2 now that I have a rotary air compressor that can run constantly, I'm getting very tired of zip tying a hand air gun and having hoses hanging all over the machine to get the chips out.

Thanks again for letting me pick your brain.


Eldar Gerfanov (Admin)

March 4, 2018, 12:40 pm

No problem!

Getting questions and feedback is great.
Any time i feel like the question is difficult, or i can not answer it to satify the user asking it, i realize i need to do some work on the app and maybe my understanding of machining.

The HP/Roughing end mill tool type encompasses both the serrated roughers and newer variable flute cutters. Basically anything that the tool manufacturers market as High Performance.

Both types allow to take deeper but still stable cuts.

I did not want to separate them because regardless of the difference in exact mechanism they work, i was not able to find sufficient differences that would prompt a separate tool type....

I get thus questions fairly often, though. So i think i will make another tool type for serrated roughers.

Big thanks for the feedback and your questions!:ernaehrung004:

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