Coolant in a hsm pocket in 15-5Ph?

TRussell said:

I need to cut some pockets in 15-5 180-200ksi. I'm using a .500 five flute, MDC coating with a .19 radius tip.
I've watched a few Youtube videos, and it seems like some people use coolant, and some don't. I'm worried about toasting the tool helixing down to the bottom of the pocket. Will coolant be necessary? I've never cut 15-5 dry before, I'm pretty sure I can get away with roughing the outside dry, but I wonder about the pocket.

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barbter said:

I've never had any luck running dry. Tried it a few times and melt down.
I've always run with coolant at 8-10% and when tools finally dull, they have tended to go 'slowly'.
Rather than bang...

Also, coolant helps washing the swarf out when you're top down (vmc) machining.
Hori - not so much of a prob as gravity is more on your side.

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TRussell said:

I've never tried running dry before, so I'm happy to hear from people with actual experience. I've seen a few Youtube videos, but they are almost all running open high speed toolpaths, also they all only run for a few minutes. I need to run for about 20 minutes

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Matt@RFR said:

Sounds a lot like you're talking about standard "old school" techniques. Chip clearing with HSM toolpaths is generally not an issue at all, coolant or not. And even if you are talking about HSM, you should still not be seeing sudden tool failures unless you simply have bad parameters.

The choice between coolant or no coolant is in coatings and SFM. You mention a coating but it looks to be a proprietary one, and you make no mention of SFM. If you're going to be in the 300-400 SFM range with a relatively large stepover, yes, coolant. 600SFM? No coolant. Between there is up to your testing.

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barbter said:

I remember 304 running a 12mm dia 5 flute variflute at S3500 F2500 with a 1mm stepover
303 12mm dia 5 flute at S5000 F3000 and a 1.5mm stepover which would run all day and some.
This was both wet.
Dry and nope.

With HSM LOC plays a big part in chip shape - we would run a 12mm @ 18mm deep so we'd get long swarf which in pockets would bind if dry. That's what I was getting at.

As an side, we'd run trocoidal in ally too. 14mm 3flute MAFord knuckle @ S10000 F5000 (upto 7500) with a 30% stepover and 20mm LOC. That would produce a shit ton of swarf but we had strong coolant pumps which would wash it all out. Most of our product was ideal Hori work but...

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