Reverse on South Bend 9" lathe
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  1. #1
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    Default Reverse on South Bend 9" lathe

    What is reverse used for on a South Bend 9" lathe? It would be nice to use reverse to thread away from the chuck, but with the chuck being a screw mount, it's not a good idea.

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    Left handed threads needs the lathe carriage run in reverse (more specifically, run left to right).

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    Thanks! Left handed threads must have been more in demand in the olden days.

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    Left handed threads are in every day use on all sorts of rotating equipment. Buy a 2 wheeled grinder and see first hand. That reverser on a 9" is not only for threading. It is for all sorts of machining. The spindle still turns toward you it just reverses the leadscrew.

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    Speaking of which, I recently turned up a few tailstock centers, running the motor in reverse and feeding the 60 degrees from the backside of the toolpost. Had to swing the compound to the right to keep it out of the chuck. It works just fine as long as you keep the depth of cut moderate. I generally used .010 DOC in that way on mild steel with HSS no problem.

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    Are we talking reverse of the motor (so that the top of the work is rotating away from the operator) or reverse of the feedscrew?

    For left hand threads, I would think it would work just fine to run the lathe in the normal direction, and reverse the feedscrew. I've never tried it, so perhaps I'm missing something.

    I have on occasion found it convenient to reverse the motor. I think similar to what pavt says, the geometry sometimes works out better to cut on the opposite side, like on the inside of something.

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    Just for reference, the thread in the tailstock ram is a left hand thread. Any turnbuckle will have a left hand thread on one end. Left hand threads are not all that uncommon. But cutting a left hand thread does not involve running the spindle in the reverse direction--only the carriage direction.

    Cutting anything from the front side of the workpiece with the spindle running in reverse involves inverting the cutting tool which will cause the carriage to lift from the cutting forces. The carriage was not designed to work in this manner.

    I find that it's often very convenient to run the spindle in reverse to cut a small chamfer on the end of a piece I've finished turning but this is done with the tool at the back side of the work. It sometimes involves less tooling change and fiddling around to cut it that way.


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