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On a commercial carbide holder...

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  • On a commercial carbide holder...

    On a commercial carbide-insert lathe tool, why is there a "spacer" (or in some cases a second insert) under the main cutting insert?

    Doesn't seem to be all of them, but I've been using a handful of different carbide holders over at the college recently, and most of them seem to have both an insert and a spacer/shim or second insert under the main one.

    Is that so if there's ever a "crash", the base of the pocket isn't ruined? Or is it an "adjustment" to compensate for different insert thicknesses?

    Doc's Machine. (Probably not what you expect.)

  • #2
    Most often they are seen on negative rake tools and they are a support pad.Those tools are capable of some pretty heavy even interrupted cuts and the insert needs a backer that is harder than the toolsteel body of the holder.

    They do help in an impact,but you really have to do something bad to bust the pad too.

    And yes they can be used for different thicknesses of inserts.I have some holders that use both .125 and .1875 inserts,they have two different pads for that reason.

    [This message has been edited by wierdscience (edited 12-11-2004).]
    I just need one more tool,just one!


    • #3
      On some of the "stacked" inserts I have used the second (top) insert was a chip breaker. JRouche
      My old yahoo group. Bridgeport Mill Group


      • #4

        They are also used with threading inserts to adjust the helix angle with full form threading inserts (mostly square, trapizoidal, butress, Acme, Stub Acme, ball screw, or other special thread forms with helix/insert clearance problems) - these particular inserts are specific angles ground into them to adjust theclearances for the helix angles of the inserts.

        The carbide seats also prevent rubbing wear of the tool holder and have greater stiffness for ceramic inserts that cannot tolerate bending.