Sherline lathe cross slide binding

[homebrewed]

Although having never used any Sherline products, I have a gripe about the plastic gibs. Yes EMCO had them in the Compact 5, a lathe considerably larger. But wouldn't it make more sense to create gibs out of brass or even copper? I have an old Edelstaal Machinex 5 and even it has brass gibs.

Many plastics are very abrasion-resistant. On top of that, you can get some some that have added molybdenum disullfide so they have built-in "lubricity". I bought some MDS-impregnated nylon specifically for making gibs but haven't got around to making any yet. I bought it from McMaster-Carr. The cast stuff is less expensive than extruded but it's a little rougher due to being sawed up after being cast. It machines quite nicely -- I learned that when I made some carriage slide plates with it. Dick "Old Toolmaker" recommended it.

One downside to using plastic is that grit can become embedded in it, causing it to become more like sandpaper. So it's important to make sure that all the bearing surfaces are very clean.

 

[Karl A]

The crosslide on my Sherline lathe had several regions of greater resistance in its travel. I decided to do something about it after I found that the crosslide had drifted after I set it to obtain a specific depth-of-cut.

I removed the crosslide and its parts from the lathe. In inspecting the parts, I found that the anti-backlash nut did not rotate easily everywhere on the leadscrew; there were areas of resistance. Inspecting the leadscrew using a 10x loupe, I saw metal chips. I cleaned the leadscrew and nut.

I don't know how metal chips got onto the leadscrew. I don't use pressurized air or gas to blow away chips.

After reassembly, the crosslide is behaving better. The regions of greater resistance are gone.

I don't know that the crosslide is behaving perfectly.
- The handwheel has more resistance when I turn it clockwise, compared to when I turn it counterclockwise.
- At very slow turning rates, the movement is jumpy and I can hear creaking. At a turn rate of one graduation (0.001 inch) per second, the turning is smooth.

Karl

 

[skogkatt007]

It's a plastic gib. It shouldn't seem a surprise tjat chips worked their way underneath it. I had a similar situation with a Unimat 3, althougj in that case I basically caused the problem. A chip got dragged across the soft cast iron and made a distinct scratch. An old time machinist friend helped me get rid of it.

 

[Smithdoor]

I picked up a new Sherline lathe and mill to get into machining, so far the mill has been great however I'm running into some issues with the cross slide on the lathe and can't figure out if I've not setup the machine correctly or if there's something else going on.

For the first 50% of travel the cross slide feels fine and just like other handwheels, however at about 50% I start getting some binding that increases to the point where I can't turn the the handwheel anymore. The binding is at a specific rotation of the handwheel(i.e. the first 50% of the turn is normal and second 50% requires increased force). I've removed/rethreaded it multiple times, adjusted the gib, backlash screw and made sure all surfaces are properly lubricated. Having the gib looser gives me a larger range I can "use" but then the cross slide has more play in it than I think it probably should(and it still starts binding).

I've got a query out to Sherline but anything else I should consider or do I just have a bad cross slide?

It sounds like the cross slide nut is to tight.
On use equipment and sometimes on new the screw is different in center. You find that some try make like a ball screw with zero clearance. But does work on screws. You need clearance at both ends.

On used equipment a lot will try take all clearance and wonder why does not work like use too.

Dave

 

[homebrewed]

The crosslide on my Sherline lathe had several regions of greater resistance in its travel. I decided to do something about it after I found that the crosslide had drifted after I set it to obtain a specific depth-of-cut.

I removed the crosslide and its parts from the lathe. In inspecting the parts, I found that the anti-backlash nut did not rotate easily everywhere on the leadscrew; there were areas of resistance. Inspecting the leadscrew using a 10x loupe, I saw metal chips. I cleaned the leadscrew and nut.

I don't know how metal chips got onto the leadscrew. I don't use pressurized air or gas to blow away chips.

After reassembly, the crosslide is behaving better. The regions of greater resistance are gone.

I don't know that the crosslide is behaving perfectly.
- The handwheel has more resistance when I turn it clockwise, compared to when I turn it counterclockwise.
- At very slow turning rates, the movement is jumpy and I can hear creaking. At a turn rate of one graduation (0.001 inch) per second, the turning is smooth.

Karl

I made a version of the Sherline anti-backlash scheme for the X axis of my mini mill and have noticed the same asymmetry in the torque (clockwise vs. anti-clockwise). I believe it's due to my external nut rotating just a tiny bit, loosening and tightening on the feedscrew as the feedscrew is rotated. You may be experiencing a similar thing.

 

[Karl A]

It's a plastic gib. It shouldn't seem a surprise tjat chips worked their way underneath it. I had a similar situation with a Unimat 3, althougj in that case I basically caused the problem. A chip got dragged across the soft cast iron and made a distinct scratch. An old time machinist friend helped me get rid of it.

I removed the gib, and inspected it using a 10x loupe. I saw a few flat/thin aluminum chips on it. I didn't see any iron or steel chips, although the dark gray color of the gib would make any such chips difficult to see. I smoothed the surfaces of the gib a little, by rubbing them in a figure-8 pattern on 2,000-grit abrasive paper, which was on a glass plate. I didn't detect any difference in function after reinstalling the gib.

 

[Karl A]

I made a version of the Sherline anti-backlash scheme for the X axis of my mini mill and have noticed the same asymmetry in the torque (clockwise vs. anti-clockwise). I believe it's due to my external nut rotating just a tiny bit, loosening and tightening on the feedscrew as the feedscrew is rotated. You may be experiencing a similar thing.

The direction of friction when turning the feedscrew clockwise is the same direction as tightening the nut. Thus, your explanation fits.

I realize from hour post that the anti-backlash nut is optional. In contrast, the gib is not. I intend to try the crosslide without the anti-backlash nut, to gain experience and understanding of the crosslide's function.