Fracturing HSS end mills

GeoLane at PTD dot NET · 2009-02-21T01:55:54+00:00

I wrecked two 1/2" two flute center cutting end mills in a row. I"mtrying to figure out what happened.A friend gave me a couple of cast iron clamps from his tractor wheelsto mill 1/2" keyways in. I had intended to "drill" down with the end mill and produce a seriesof overlapping holes, and then side mill the slot - cheapo me - I cansharpen the ends of end mills, but not the sides, so I try to put mywear on the ends.I moved the table up until the end mill was just touching, thenstarted to pull down on the quill handle. I was putting a fair amountof pressure on to get it to cut and it just grabbed and fractured. Thefirst time I could blame it on the vise and work piece not beingclamped tight enough. The second time the cast iron work piece movedless in the vise when it grabbed than before, but it still moved whenthe end mill grabbed. After this I did the slot in the conventionalway, side milling out the metal. I didn't feel any hard spots when Icame in from the sides. What happened? Doesn't cast iron like to be drilled with an end mill?It seemed to work ok when I was feeding the table up to get intobright metal, but when I pulled down on the quill handle, it brokeapart. Did I put too much pressure on with the quill lever? Thoughts?RWL

Feb 21, 2009 20 Replies

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steamer 17 years ago

--Next time use a stub drill and grind the flutes as you would for brass. More strength that way and you'll be more likely to get thru the scale/hard zone in one go.

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