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milling 17-4PH stainless

RE. my last post on buying carbide end mills.

THe job I was doing when I killed the two 3/4" x 2.25" LOC carbide ends mills was milling a slot in 17-4PH annealed stainless. About 32 Rockwell C. First end mill was run at S651 F4.67 really badly chipped after first piece.

Second one was run at S300 F3.10 I got throught 1/2 a slot when I got a X-axis overload. It had started to pull the part up out of the vise and was cutting in deeper.

Finished that part and the last one with a HSS end mill, uncoated, at S212 F1.49 and it worked nicely, but alittle slow.

Job is done, but why was I killing end mills? First end mill was run at speed and feed I found for a carbide finish end mill. Second F&S was from a table in an OSG book for carbide roughers.

4" round bar clamped tight as hell in a kurt vise with 3" tall jaws.

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Reply to
Randy
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Your surface speed was way too slow, suggest next time start around 180 = sfm and work upwards from there.

As a point of refrence, I use to mill that stuff in the annealed = condition pretty without coolant much all day long on a bridgeport hand = mill at a speed where chips just barely begin to turn a light amber = color.

Avoid re-cutting of chips like the plague.

Other caveat being it will work harden in a heartbeat if you're not = paying attention and so if it starts into skreeking at you then PULL OUT = FAST

Reply to
PrecisionmachinisT

"I use to mill that stuff in the annealed condition pretty without = coolant pretty much all day long on a bridgeport hand mill at a speed = where chips just barely begin to turn a light amber color"

To clarify, the above was done using M48 HSS endmills...

Reply to
PrecisionmachinisT

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