# Leadscrew tight to turn by hand



## duncanbojangles (Aug 10, 2014)

I'm making a makeshift power feed for my 1921 13" South Bend from a variable speed geared motor that will attach to the tailstock end of the leadscrew. I find that the lead screw is very difficult to turn by hand. Is this normal? I've completely disconnected the gear train and even made a handwheel to fit the keyed shaft at the headstock end of the leadscrew, but it still takes quite a bit of force to even get the leadscrew to budge. The lathe threads and automatically feeds just fine under power, so I know nothing is too terribly stuck. If this is the normal state of affairs, I may have to find a beefier motor.


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## Thoro (Aug 10, 2014)

Try disconnecting the gear train from the spindle. I am not well versed on your lathe, but if it has a quick change gear box, or is geared with change gears and you haven't put it in "neutral" the it may be very hard to turn the leadscrew from that end.


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## duncanbojangles (Aug 11, 2014)

Aye, I have completely disconnected the gear train from the spindle. The only bit of the lathe that the leadscrew is connected to are the leadscrew bearings at either end of the lathe, and the apron. The funny thing is that I can sometimes get the leadscrew to turn just a bit before it becomes really difficult. As in, I'll get 1/8 of a full turn around without too much difficulty and then it becomes much, much harder.


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## ScrapMetal (Aug 12, 2014)

Okay, a stupid question then, are the half-nuts engaged or how about the clutch?

Just tryin' to think of things that would do that but still leave the lathe "operational" most of the time. :biggrin:

-Ron


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## duncanbojangles (Aug 16, 2014)

The half nuts are disengaged and the clutch is disengaged as well. After looking under the apron (oh my) it appears that the worm is very tight and difficult to rotate. The worm can be seen in this photo (taken from Ryan Battelle's page?).



There are two collars that I believe I can loosen to free up the worm some, though I'll need to read more to make sure I remove those pins properly before I damage anything.


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## Kernbigo (Aug 17, 2014)

Spray it with kroil penetrating oil and then try it, may be your oilers are all plugged up and the wicks are not putting the oil where it is suppose to be


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## duncanbojangles (Nov 9, 2014)

Sorry to revive and old thread, but I've pulled the saddle off my lathe yesterday to sort out the problem of the too-tight-leadscrew. It appears that my leadscrew is binding because the apron & saddle are higher on the ways than original (the previous owner put Turcite on the saddle) and the leadscrew is being pulled up and binding.

Here's how I figure that; If I loosen the leadscrew support at the headstock end and the leadscrew support at the tailstock end and just let everything kind of hang loose, I can spin the leadscrew by hand with the threading half nuts engaged, and also with the automatic feed clutch engaged. This is not something I can do with the leadscrew supports tightened up to the bed; the leadscrew binds quite badly. So the insides of the apron are not to blame.

So, I'll let this information digest in my head for a while before I decide what to do. I'm pretty sure I'll have to either mill material away from the leadscrew supports to raise the leadscrew, or shim the apron from the saddle to lower the apron to the leadscrew. If anyone has suggestions regarding which method is best, and how best to measure how much material to remove or how much to shim, I'd appreciate it very much.


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## lugnard (Nov 9, 2014)

Just thinking about your problem...If I follow it that is . If the apron is higher then wouldn't the hand wheel gear bind on the rack under the bed? I would lean to shimming the apron back to a more original position than removing material from the lead screw mounts. Once you mill those you are committed to that fix or replace the mounts I guess.

At least you are on to something as to the reason for the binding.

Harry


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