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South Bend SB 9 3c collet adapter

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  • South Bend SB 9 3c collet adapter

    I am sure many have seen these items on eBay

    My question for someone who has one on hand (or the similar true SB part), what is the dimension of the 3mt taper portion just behind the nose piece, that is the max outside diameter?


    cheers, Graham in Ottawa Canada

  • #2
    Here is a gif of the part:

    These were measured from a collet adapter I borrowed from a friend, it was a factory unit.


    • #3
      Thank you, that will do the trick,.

      The answer to my question and more.

      cheers, Graham in Ottawa Canada


      • #4

        The collet closer for my 12" Atlas Craftsman is made simply from cutting down a #3MT adaptor, either to a #1 or #2MT inside. you don't really need the fancy flange, although I guess it gives some protection for the spindle face. Just make sure that the through hole at the back will allow the collet easy passage.

        These come in soft+ hardened tang or case-hardened varieties, with the soft being cheaper-$9? .

        I recently changed the entry angle on mine to the 12 degrees, and from this light machining, it's obviously the soft version, and has held up perfectly since the early fifties.
        Richard in Los Angeles


        • #5
          Originally posted by RPM
          The collet closer ..... Just make sure that the through hole at the back will allow the collet easy passage.

          Richard in Los Angeles
          This is not completely true. The cylindrical area at the rear of the collet is also part of the centering. It prevents the collet from being at an angle to the axis of the lathe. So you should make the fit there a fairly close, sliding fit.
          Paul A.
          SE Texas

          Make it fit.
          You can't win and there IS a penalty for trying!


          • #6
            Thanks for all the info.

            I usually tend to fall back to KISS but also overthink something before I get there.

            Using a 4mt blank end arbor has always been one of my options. My only concern is how hard they really are. For example, I want as little overhang as possible so that would mean cutting the arbor back close to the spindle - the end is soft but would I be able to face the arbor if I cut it well back from the soft end? I know the other end is reasonably soft as well. I have cut the back end of with a cutoff wheel and faced off, and drilled and tapped for drawbar on several all ready. I am no stranger to the blank end arbors as I use them frequent to make specialized too holders.

            So, I guess the question really is (and one to which I don't have a very clear answer) are these blank or soft end arbors really case or flame hardened where they are not supposed to be soft leaving the insides relatively soft or are they hard all through? I suppose the answer is "It depends, on the source and manufacturer".

            I don't have any 4mt blank end arbor to hand and seeing as that is the direction I am leaning to at the moment perhaps I should just get a couple and "just do it".

            cheers, Graham