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Work Hardening?

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  • #16
    I'm with Evan and from boring hard material or material that work hardens such as SS and special alloys if I slow the spindle speed and take the same DOC the tip lasts longer and the finish is acceptable.

    Lately I have been turning a lot of SS, Monel and Hastaloy. The SS tends to work harden with high speed and light cuts, the Monel cuts nice but is hard on cutter edges and work hardens and the Hastaloy is murder on cutting edges and really likes to work harden if cut fast dry and allowed to get hot.

    OD turning is not to difficult to control but boring is tricky. Make a drawing of a bore with the cutter taking a cut and see how the tool is loaded as the cut is being made. You will see the material is coming down on the top of the cutter with the force going from the rear toward the tip of the cutter. When your boring the forces are much higher and tend to break the tip much more than for OD turning.

    A little back rake when boring is a good practice also few thousandths below center won't hurt. If your above center and the cutter is horizontal the load on the cutter is real high and it's more like your rubbing the metal off rather than cutting it off. At that point your work hardening the material much like burnishing it as you bore it.
    It's only ink and paper