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Luxcut lathe lash question

F

fireguyfire

Member
I’m getting my newly purchased Luxcut 1136 lathe “tuned up” and so far everything is going well.
The thrust bearing on the compound felt a tiny bit crunchy when winding it, which isn’t surprising since they would be the most used part of this 1978 lathe. I replaced the bearing and now it cranks beautifully, but it another issue I would like to address has surfaced and I’m in need of advice.
I’ve got a fair bit of lash it the compound screw; the gibs are adjusted perfectly and there is no perceivable side to side play, but there is a fair bit longitudinal along the line of the screw; I can turn the handle around a 1/4 turn in each direction before I get movement of the compound.
I’m assuming that I have wear in the brass/bronze compound nut? I’ve checked the lash with the compound full extended, retracted, and in the middle of its travel and the lash seems consistent.
Is this a common thing on “older” lathes, and is replacing the compound nut something I should do, and if so, where would I buy one?
 
99% chance if you want to replace that compound nut you will need to make it, most likely acme threads, a project for later when you have some hours *IF* you really really want to

But I wouldn't worry about it to much, the lathe will still function fine, when moving the tool in and out you have to dial out the backlash anyhow, you will never have zero.

I crank my stuff out a full turn, if i was at .120 on the dial, i crank out to .120, move the carriage, and crank it back in to .120 plus whatever the next cut will be.

A full turn is easy to remember, and no matter your lathe you should have the backlash out in a full turn...if not, then its time to look at things
 
@fireguyfire : yes, very common. It can be the nut, but is typically a combination of both. Depending on the complexity of the cross feed screw it may be something to make? The “nut” is typically bearing bronze and can also be made.

I have found it odd, that despite the “sacrificial” nut material (bronze, cast iron) the screw still tends to also loss tolerance.
 
Yes, I read up on this issue in the internet and it sounds like it can be the screw, but or both.
The recommended test was to turn it all the way in, all the way out, and test the lash in the middle where it gets all of its use. If the lash is the same in all 3 locations it’s likely the nut, but if the lash is more pronounced in the middle of the screw travel it’s more likely wearing of the screw.
Don’t k ow if that correct but it makes logical sense to me.
Mine is the same at all points along the screws travel length.
 
@fireguyfire - A half turn seems excessive for play in the nut. Don't forget to check the screw anchor. Any play in the anchor will feel and act like backlash in the nut. You can check for it by looking for longitudinal movement of the screw with a bit of extra friction in the Gibb. Sometimes it's easy to fix and sometimes it's a bitch.
 
I haven’t had a compound on my lathe for at least five years. Solid toolpost and a DRO means I have an exact X Y position of the cutter. Only time I’d ever need a compound is cutting a short taper, and haven’t done that in decades. Even cutting threads, I’m using the solid toolpost and @jcdammeyer ‘s ELS with the cutter feeding in perpendicular to travel.
 
A thought; as I mentioned I replaced the thrust bearings at the handle end of the screw where it anchors to the compound.
There is a tightening nut under the scale sleeve to tension the thrust bearings and I couldn’t find a torque spec.
Is it possible that under tensioned thrust bearing on the end of the screw shaft would translate as lash?
I just tightened the tensioning nut until the bearings felt smoothe when the screw handle rotates and called it good.
 
fireguyfire said:
A thought; as I mentioned I replaced the thrust bearings at the handle end of the screw where it anchors to the compound.
There is a tightening nut under the scale sleeve to tension the thrust bearings and I couldn’t find a torque spec.
Is it possible that under tensioned thrust bearing on the end of the screw shaft would translate as lash?
I just tightened the tensioning nut until the bearings felt smoothe when the screw handle rotates and called it good.
Click to expand...

Yes. This is likely your anchor that I discussed above. Longitudinal movement of the screw should be minimumized and will show up as backlash even if the leadscrew nut is tight and has none.
 
Can anyone suggest the best way to go about tightening up the thrust bearings to remove the lash?
I do t want to over tighten and damage the new bearings.
 
fireguyfire said:
Can anyone suggest the best way to go about tightening up the thrust bearings to remove the lash?
I do t want to over tighten and damage the new bearings.
Click to expand...

The user manual should describe how that is done on your lathe.

In the absence of a manual, I'd tighten it up good and solid, and then back off till the crank turns smoothly. It's really hard to damage thrust bearings. Run it like that for a month or so, then repeat.

You can also review the manuals for other lathes with a similar design to get an idea of what might work best for you and your lathe.
 
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