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Sherline Leadscrew Binding In One Direction

Discussion in 'SHERLINE, TAIG, TITAN & SIEG MINI-MACHINES' started by jhmiii, Sep 17, 2016.

  1. jhmiii

    jhmiii United States Iron Registered Member

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    This problem has arisen recently and I have not been able to figure out the source. I was seeing a lot of movement in the cross slide while cutting and getting chatter as a result, so I adjusted the gib for a tighter fit. All was well for a few months, but now I am experiencing difficulty turning the leadscrew to move the cross slide toward the head. It binds so tightly that it is difficult to move even when not cutting. Turning the leadscrew to move the cross slide away from the head is perfectly free and normal. My lathe is about 10 years old. Could this be a signal for a new leadscrew nut?

    Appreciate any and all insights.

    John
     
  2. JimDawson

    JimDawson Global Moderator Staff Member Director

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    Is it possible that the gib is moving around a bit? I had this happen once with a tapered gib where one of the end stop screws worked loose.
     
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  3. karim

    karim United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Does your machine have the brass lead screw backlash adjustment nut? I'm not sure when those were added. If it does, is it possible while you were adjusting the cross-slide gib, you misadjusted the backlash adjuster?
     
  4. mikey

    mikey Active User H-M Supporter-Premium

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    Sounds like the saddle nut needs to be adjusted. Look under the saddle, on the right bottom. There should be a socket head cap screw flanked by two set screws. That cap screw locks the saddle to the nut. You need to run the saddle as close to the tailstock end of the lathe as you can (remove the tailstock) and adjust it there. Loosen the cap screw slightly - you do not need to have it super loose - and work with the two set screws to balance the forces on the nut; adjust one and then the other until the saddle runs free without binding. Gently tighten the cap screw and retest. When it runs free both ways, you're done. It takes a few tries but this should resolve the issue unless the nut or screw is totally messed up.
     
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  5. jhmiii

    jhmiii United States Iron Registered Member

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    It was the saddle nut! Followed Mike's instructions and with some fiddling was able to obtain a nice smooth motion in both directions without any saddle movement during cutting. Was able to finish the boring job for a guided die holder. I had to buy a special die for cutting left-handed threads and it is larger than my other dies (1" vs 0.75"). Thanks for the input Mike, Karim and Jim. Have a great weekend.

    John
     
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  6. RJSakowski

    RJSakowski H-M Supporter - Premium Content H-M Supporter-Premium

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    It appears the Sherline uses a tapered gib to adjust cross slide play. They have only one locking screw to hold the gib in place. There will be a small amount of movement pushing the gib tighter as you advance the cross feed and pulling it looser as you retract it. Their gib is also self lubricating and possibly, by tightening the gib, you restricted the amount of lubricant causing starvation and increasingly more difficult movement.

    I would try loosening the gib to see if that cures your problem. If the problem is in the thrust bearing or the lead screw nut, it will still be there. If it goes away, it's your gib adjustment.

    I have seen binding issues with the thrust bearing as well. You might want to investigate that area. Another possibility is in the dial. I had a binding issue with my lathe in that regard. Readjusting the dial cured it.

    edit: your post above occurred while I was writing. Glad you got it sorted out. Most of these problems aren't too difficult if you take the time to analyze them and eliminate them one by one.:encourage:
     
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  7. mikey

    mikey Active User H-M Supporter-Premium

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    Glad that worked out. That saddle nut is a pain to get adjusted sometimes but it should stay that way for a very long time. If that turns out not be the case then you need to replace the nut. The Sherline lathe is incredibly accurate - if you dial in half a thou, it will cut half a thou. One of the reasons for this is that saddle nut. When adjusted well it tracks the nut on the rolled leadscrew very accurately.
     

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