Speeds and Feeds for uncoated carbide

I have recently started using uncoated carbide inserts and was wondering if there is a rule of thumb on how fast to run them and how hard to feed them over HSS. I was machining a piece of 3" gray iron that would eat even a 10% cobalt bit. I switched over to a C2 uncoated carbide and running in backgear at 180 rpm and a depth of .003 with a feed of .003 it machined like a dream with a very nice finish. In HSS this would equate to around 133rpm using 4C/D where C= cut speed of material and D= Diameter.

I then had to bore the piece out and used a Carboloy 883 brazed 1/4" bit in the boring bar using the same speeds feeds and depths of cut and again it cut very well with no chatter.

So is it fair to assume that when using uncoated carbide that you can increase your speed by 30-50 percent over HSS speeds? I tried to check the Kennametal, Valenite, and Carboloy websited and didn't have any luck finding recommended feeds and speeds for uncoated carbide. I also checked

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and couldn't find any info either.

Thanks for any help. -Steve

Reply to
Steve
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30-50%? I suppose you can if you want to (although running carbide too slow can be detrimental) but normally I run inserts at 3-5 times the speed of HSS. This will yield a superior surface finish (may look like a ground shaft at a quick glance) and if you have a chipbreaker, it will actually work.

If you're being paid for your work, you may find it more economical to run faster. You'll have to index your inserts more (obviously).

Bottom line: run them as fast and as hard as a) your spindle can take without stalling, b) the inserts will give economical life and c) you're personally comfortable going. Those chips are flipping hot and they go everywhere when running most inserts at the correct feed and speed.

YMMV.

Regards,

Robin

Reply to
Robin S.

My experience is with industrial-strength CNC equipment, so may not apply to you. I would expect uncoated carbide to run at least triple the speed of HSS in cast iron. I'm talking theoretical tool wear, not taking into account machine and workpiece rigidity, etc.

Reply to
Michael Rainey

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