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Do 3C collets have internal threads for a stop?

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  • Do 3C collets have internal threads for a stop?

    One of my machining students wants to make a collet stop for his 3C collets and I told him I'd draw it up for him, but I can't find any specs on an internal thread on them. I obviously don't have one handy or i wouldn't be asking, but do they have inside threads? If so, what is the major, minor, and pitch diameter? If not, is the bore at the end of the collet a consistent enough size to make an expanding stop and what would that bore size be? Thanks a lot!

    Stuart de Haro

  • #2
    Not that I know of.... and I use them in my Logan.

    Bore is all over the place, 0.450 to 0.525, depending on size. That's with Hardinge, S-B, and others.

    Keep eye on ball.
    Hashim Khan


    • #3
      That makes the project a little problematic. Thanks for the info.
      Stuart de Haro


      • #4
        Unfortunately, I don't have my camera. I have two collet stops which work without internal threads. One is for W20 collets---a very close size and capacity to 3C---and the other is for 5C. The one for W20 has four captured ball bearings in a sleeve. The rear of the sleeve is tapered larger than the collet ID, but not larger than the collet OD. A knurled nut threads into this sleeve with a tapered front projection. As you screw down the nut, the tapered portion expands the ball bearings to grip the ID of the collet. Through all of this is a rod secured by a set screw through the knurled expanding nut.

        It works very well. The 5C is a little different construction but works on the same principle. Here is the Travers Tool listing for the product: McMaster sells them also. They are called "Speed Stop". It works with a captured, split plastic sleeve. There is a tapered section in the front. An opposite taper is on a female threaded nut. As you screw the nut on, it forces the plastic sleeve to expand on the opposing tapers. Once again, there is a sacrificial rod held with a set screw to hold position of the stop.

        Hopefully you are able to make something similar. If my explanations could benefit from further detail, feel free to ask.