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Touching Up a 3 Jaw

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  • Touching Up a 3 Jaw

    My old Skinner 3 jaw has some "bellmouthing?" At any rate when I clamp a piece of stock long enough to reach into the master jaws I can see cracks of light at the ends of the mounted jaws. Sounds like bellmouthing to me!

    So far I've searched and reviewed past posts on TP grinders but I'm left with some questions over the actual stones. Type, dia, dressing, etc.

    What I've got is a Taiwan air grinder nameplated at 22K for rpm. 1/4" shank. I'm not thinking I need an extra rigid setup here because all I want to do is some touch up work. A 1/2" shank welded to a section of tubing and some hose clamps over another section to clamp it in the middle is quick and dirty. I need a 2-3" reach to get to the back of the master jaws and on a 1/4" shank ain't none of this gonna be rigid. Lots of spring passes while watching the sparking?

    I thought I read somewhere on here 5-6K SFM is best for grinding, so I'm thinking a 1" dia. stone, but please, any advice is welcome. Haven't a clue on what type, grit, and so on.

    I have read all the precautions on grinding dust and fully intend to follow the "safe sex" advice I give all the Young and Horny Painters! LOL! Cover it up guys .....

    There's a 2" thru hole in the chuck so I'm thinking I'll need a ring of some sort on the outside of the the jaws to tighten them up in that general area. And that is just about everything I can think of on the subject.

    So whaddayu guys think? Proceed or give this up as a lost cause?


  • #2
    When you are true-ing up chuck jaws, thay must be loaded in the same direction they will be used.

    True passes are easiest on the external jaw set, because you can move a tube section to different steps. Same is true of the internal (outward expanding steps).

    The problem comes in where you are grinding the master jaws, and matching OD grabbing jaws. They need to be loaded toward the center. While I haven't done it, I would place a soft plug that bears on the master jaw teeth that engage the scroll. Then grind the master, and the removable jaw.

    I have also heard of using a thin tube to preload the jaws, do part, move the tube, do more.