CNC Problem breaking end mills can anyone help?

Hi all group, having to come in through google as the news server I
normally use now requires a password?
Anyway, trying to mill a block of commercial grade steel, EN3 I think!
The mill I am using is a 1/8 Inch shank slot mill and have now managed
to break 4 (2 short and 2 long shank).
I have to plunge down into the steel, fine no problems, and then do a
the first pass at depth, snap goes the mill.
Now I did not consider that I was asking too much but must be, depth
2mm, feed 37.5 mm per minute and speed fastest I can go at 1600 rpm.
That gives a load per flute of 0.0004 thou. Sorry to work in both
metric and imperial but I do that at times.
Can anyone let me know if the figures are way out and what should I be
running at. I can take the depth down to 1 mm.
Cutters are Clarkson and have a 46.51 lead which I guess is the spiral
in the flutes in case I am using the wrong cutters as supplied.
Thanks in anticipation
Adrian
Mill at
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Reply to
Adrian Hodgson
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Your speed is about 1/2 what it should be.
Reply to
Steve Blackmore
2mm is pretty deep for a 1/8" cutter. That's like 8mm on a 1/2" cutter and I wouldn't fancy trying that. I use 3mm slot drills on one particular job but I only tickle 10 or 20 thou or so at a time out with them. Mind you I hate breaking stuff and prefer to take longer than spend out on tooling. Try 1mm and two passes or even 0.5mm and four passes and see if things improve. Sometimes once you've got the depth right you can up the feed a bit and recover some of the production time.
Reply to
Dave Baker

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