Sherline 5410 Rough X Axis

adam.mccormick

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I just "downgraded" my mill and lathe from CNC to manual (CNC isn't really my thing, it's not as fun or as satisfying as manual work for me). I bought (mistake) the necessary replacement parts, lead screws, and a few odds and ends required to convert them back to manual. Everything went fine except for the X axis on my mill. When I feed the table in, everything is smooth, but feeding out (counter-clockwise) it almost binds right up and there's a grinding feeling. I'm pretty sure the grind is the boss on the end of the leadscrew rubbing against the thrust collar. It's supposed to run against it so I have no idea why it's so rough. I also can't for the life of me get the final play out of the handwheel. No matter how firm I think I have the leadscrew and handwheel it will always loosen up by about 1/8th of a turn.

Anyone had this kind of problem before or have any idea what I might be doing wrong?

Thanks!
 
There isn't much to the X-axis. If I had to guess, the issue is from one of two possibilities - the backlash adjuster is not right or the nut in the center of the saddle is not in the right place, or possibly both. Here is what I would try:
  • Loosen and back off the backlash adjuster. I assume you have the newer star gear type lock. Loosen the one with the hex screw so that the gear can disengage from the backlash gear that the leadscrew runs through. Back off tension on the backlash gear so there is a little play.
  • Loosen the gib so you can work.
  • The leadscrew nut for the X-axis is in the middle of the saddle, underneath the table. You will need to turn the X-axis handwheel CCW to move the table almost all the way off so you can access the set screw that holds the X-axis nut in place. There is a shoulder that this X-axis nut must seat against. If it is out of position it can cause movement and binding. Gain access to the set screw and loosen it slightly, then pull on the X-axis hand wheel to pull that nut up against the shoulder, then lightly tighten the set screw to lock it down. Do not put excessive pressure on the set screw or you will distort the thin wall of the nut; you only need to lightly snug it. Now crank the table back into position so the middle of the table sits over the saddle.
  • Re-adjust the gib. I find it best to make the gib a little too tight, then tap it loose until the table just start to move smoothly. There is no drag but there is also no play when you rock the table. Then lock the gib down.
  • Now you can adjust the backlash gear to remove play in the leadscrew. You have to play with this because as you tighten the lock down gear the backlash setting can shift. You'll figure it out.
Give this a try and let us know if any of it helps.
 
Thanks Mikey! Although I'm not exactly sure if that was the main problem I just rebuilt the X axis entirely and made sure to check that the leadscrew nut was seated as you suggested. It seems to be in order now.

By the way, what kind of backlash do you get on your machines? I have about .04mm (~0.0016in) after putting the X axis back together. This was about as good as I could get it. The anti-backlash nut is real fussy and goes from too loose to too tight if you look at it wrong...
 
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I have the old style backlash adjuster nut and it was easier to use in my opinion. Backlash on the mill is fine anywhere under 0.002" because we are typically milling conventionally, not climbing (except for fine finishing passes). More important than perfect backlash settings are your gibs.

Most Sherline guys don't realize how good the gibs are and how big a role they play in the accuracy of their machines. I recall one guy I saw on Youtube lapping the gibs so they were flatish and he seemed to think this was rightish. If you take a good look at the Sherline gibs you will find that they make most of their contact at the upper and lower edges of the gib. This reduces surface contact or drag while also eliminating play. Not sure increasing surface contact is the right idea; I could be wrong but ...

Most guys also over-oil the gibs. A little bit of oil is okay but too much creates drag. To be honest, I think I lightly oil my gibs maybe once in a decade and my gibs have almost no wear.

The Sherline gib is incredibly sensitive. A fraction of a fraction of an inch makes the difference between smooth running and slop. It takes a bit of fussing with it to get it right but once it is set well, you need not mess with it for a very long time. What this allows your lathe or mill to do is take cuts a little machine like this should not be able to take. I've done 0.060" deep cuts on the lathe (0.120" reduction in diameter) in mild steel in a single roughing pass with zero chatter. Many larger hobby lathes would struggle with a cut like that.

Of course, this takes the right tool but that capability also relies heavily on the gibs so get them adjusted right.
 
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