Re: Speeds/feeds among diff. machines

Can you tell us what type of holder the endmill was in ? With that
small of an endmill, typically there isn't a weldon flat. That's
because the manufacturer of that endmill would like it to run as true
as possible in a collet, not an solid endmill holder with a set screw
pushing it off center and running out.

I find this more common than you could believe when it comes to
endmill failure. The pressure of a hardened set screw making contact
perpendicular to a hard carbide shank only really makes contact in 2
very small places on 2 very hard slippery surfaces. So the set screw
is cranked down on the carbide so much that the tool may crack right
there before even getting into the cutting action.

If the tool is still together at this point and is entered into the
cut, once the forces of the chipload exceed the set screw pressure on
the shank of the tool then the tool slips and becomes a shaping tool.
Since it is not designed to be a shaping tool it breaks.

Either grind a very nice flat surface where a set screw can securely
seat into to keep the endmill from spinning inside the solid endmill
holder or put it in a collet holder and tighten securely.

If all of these precautions are already in place, then you have some
serious issues with the wrong geometry of the endmill such as edge
prep, helix angle, etc.... that is causing the tool to fail as this
seems like a fairly easy application.

JR

.

Relevant Pages

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  • Re: Speeds/feeds among diff. machines
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