Re: I'm sure this has been asked before

In article <eZednRCuOur9DKTVRVnyugA@xxxxxx>, Steve <steve.withnell@xxxxxxxxxxxxxx> writes


Lots of other rules I follow, like I don't cut slots (even open ended ones) with a 4 flute cutter, you can but you shouldn't really.

This is good advice. The reason for not using end mills (4-flute cutters) for cutting slots was well explained by (IIRC) GHT in one of his books (may possibly have been Tubal Cain). Briefly, the leading tooth of a 4-flute cutter puts a sideways stress on the cutter, which means it deflects sideways a bit, thus it is not exactly where you wanted it. If it runs out (of an open-ended slot) or you vary the feed, this deflection ceases, and you get a wobbly slot; if you run back the other way, the deflection is in the opposite direction and the slot comes out wide.

Of course, best practice is to rough out the slot with one size smaller cutter and finish it with the correct size, if it is the desired width coincides with a standard size, or clean up the edges on both sides if it is between standard sizes.

David
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David Littlewood
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Relevant Pages

  • Re: Feed and spindle speeds for milling aluminum and brass
    ... | The best way to create chatter is to use high RPM, ... | with the cutter completely buried and feed slow. ... Reducing chatter ... some extent on tool deflection. ...
    (alt.machines.cnc)
  • Re: Im sure this has been asked before
    ... ones) with a 4 flute cutter, you can but you shouldn't really. ... tooth of a 4-flute cutter puts a sideways stress on the cutter, ... this deflection ceases, and you get a wobbly slot; ...
    (uk.rec.models.engineering)