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3D Printed Spindle Lock AND Indexing

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  • 3D Printed Spindle Lock AND Indexing

    The other thread on 3D printed lathe spindle locks has inspired a new application in my mind.

    I have just noticed a number of ebay ads for these locking devices for SB, Atlas and some other lathes. (

    Yes, their use as spindle locks is a great idea and I will probably print one for my SB. However, since they use the gear teeth on the bull gear, it would seem they can also be used as indexing devices. I have a back plate on my three jaw chuck with a row of indexing holes which I have used on a number of occasions. But the bull gear has a number of teeth: I believe mine has 80. This immediately allows indexing by factors of two and by five (2, 4, 5, 8, 10, 16, 20, 32, etc.

    It would be handy to have a way of locking the spindle lock down while performing these indexing operations. And one or more circular scales could be attached (magnetically?) to the spindle to make it easier to get the proper teeth in engagement. But the idea seems perfectly feasible.

    AND, if you were to print multiple spindle locks, with the position of the gear teeth moved by a fraction of the tooth spacing, you should be able to achieve other numbers for the indexed positions. For instance a set of three locks with the gear teeth moved by 1/3 of the tooth spacing would provide a new prime number in the mix so divisions by 3, 6, 12, etc would then be possible. Additional sets could introduce more prime numbers like 7, 9 (two 3s for 9 divisions) etc. Of course, all this math depends on the tooth count of your bull gear.

    Just a thought that hit me while reading that other thread. This may have limited accuracy when going to higher numbers of locks in a given set. The set of 9 to allow 9 divisions may be stretching that limit. But the idea is tempting. One way around this could be adding an adjustment screw that allows fine tuning each lock for greater precision. Or just filing the surface it rests on.

    Paul A.
    Golden Triangle, SE Texas

    And if you look REAL close at an analog signal,
    You will find that it has discrete steps.

  • #2
    Oooo I LIKE the way you think... Mine has 60 holes drilled radially in the backplate for factors of 60, but I'm not sure how many teeth the bull gear has... probably 80 like yours? Now I'm gettin ideas. How to make an indexer out of (say) brass, some time and some files. Mt head be scratchin while my thoughts be hatchin if I only had a brain....
    25 miles north of Buffalo NY, USA


    • #3
      I hadn't thought of that, but the Atlas has 60 indexing holes and a lock pin for the bull gear, so 2, 3, 4, 5, 6, 10, 12, 15, 20 and 30 positions are available. The bull gear has 69 which will divide by 3, but is designed for a hunting tooth for wear distribution.
      As it happens, I am machining 3 of the nylon spindle locks, which could be 1/3 tooth different with care and hand finishing.
      Last edited by old mart; 08-01-2021, 12:33 PM.