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Posted by Don Young on August 25, 2008, 9:40 pm
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>
> Is it normal for half-nuts on older lathes to "hang up" or not smoothly
> engage the leadscrew with each and every close of the half-nut lever?
> Not being the original purchaser of this lathe, I do not know how it
> behaved when new from the works (around 1970). The lead screw is 1-1/2"
> x 8 tpi.
>
> The half-nut hangs up say 50% of the time. A small movement of the hand
> wheel fixes the problem by shifting the carriage slightly. I've taken up
> using the thread dial to guide the timing of the closing of the
> half-nuts, but even this dodge does not provide a smooth close 100% of
> the time. Sometimes the half-nut grabs on the outside of the leadscrew
> (land?). At other times, it does not appear to want to close more than
> half of the normal distance.
>
> The leadscrew has been cleaned of all chips, swarf, compacted dirt etc.
> The half- nuts have been removed and similarly cleaned. The half-nuts
> close cleanly on the leadscrew when they are off of the lathe. Wear does
> not "appear" to be excessive. The OD of the leadscrew is the same at the
> ends of the screw and in the middle (no wear?).
>
> If this behavior is not normal, what can be adjusted or where should I
> look to find the problem?
>
> Thank you in advance for any insight you can provide.
>
>
> --
> PointFive
> ------------------------------------------------------------------------
> PointFive's Profile: http://www.rcgroups.com/forums/member.php?u=225133
> View this thread: http://www.rcgroups.com/forums/showthread.php?t=914362
>
It seems to me that what you describe is normal operation. The half-nuts
cannot fully close unless they are in alignment with the thread on the lead
screw. Unless you have a lot of backlash, careful attention to the thread
dial should permit closing at the proper time/position. The thread dial may
need some adjustment if it is not indicating properly.
Don Young (USA)
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> Is it normal for half-nuts on older lathes to "hang up" or not smoothly
> engage the leadscrew with each and every close of the half-nut lever?
> Not being the original purchaser of this lathe, I do not know how it
> behaved when new from the works (around 1970). The lead screw is 1-1/2"
> x 8 tpi.
>
> The half-nut hangs up say 50% of the time. A small movement of the hand
> wheel fixes the problem by shifting the carriage slightly. I've taken up
> using the thread dial to guide the timing of the closing of the
> half-nuts, but even this dodge does not provide a smooth close 100% of
> the time. Sometimes the half-nut grabs on the outside of the leadscrew
> (land?). At other times, it does not appear to want to close more than
> half of the normal distance.
>
> The leadscrew has been cleaned of all chips, swarf, compacted dirt etc.
> The half- nuts have been removed and similarly cleaned. The half-nuts
> close cleanly on the leadscrew when they are off of the lathe. Wear does
> not "appear" to be excessive. The OD of the leadscrew is the same at the
> ends of the screw and in the middle (no wear?).
>
> If this behavior is not normal, what can be adjusted or where should I
> look to find the problem?
>
> Thank you in advance for any insight you can provide.
>
>
> --
> PointFive
> ------------------------------------------------------------------------
> PointFive's Profile: http://www.rcgroups.com/forums/member.php?u=225133
> View this thread: http://www.rcgroups.com/forums/showthread.php?t=914362
>