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Tapered Gib Mod For 7x10 Lathe Without A Mill?

Discussion in 'HARBOR FREIGHT, CENTRAL MACHINERY & BUSY BEE' started by Cavediver, Mar 2, 2016.

  1. Cavediver

    Cavediver United States Active Member Active Member

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    Now that I have my headstock issues about wrapped up, it's time to move on to the rest of the lathe. First up is getting the saddle squared away.



    The "Saddle Retaining Strips" are as tight as they can be and there's still a lot of vertical play: .004 at the front, and .006 at the rear. It's time for plan B or C.

    Plan B is to do the tapered gib modification and is the direction I would like to go, but I don't have a mill. Is it possible (and reasonable) to pull this off without a mill?

    I've done a lot of thinking, looking, and measuring to try and figure out an alternate method of doing this work. Aside from a ton of hand work with files, scraping tools, and a hacksaw, I just can't see it. However, given the huge pool of creative machinists here, I thought I'd ask before preemptively throwing in the towel.

    Tools I do have access to: Lathe, bench top drill press (loose at best), all sorts of hand tools, table saw, and an industrial CNC router (at work). I don't have a ton of measuring gear, but I should have enough to get the job done.



    Plan C, as much as I hate to admit it, consists of varying thicknesses of brass shims, some clamps, and a few drops of super glue to build the contact surfaces of those brackets up to the correct level. Not perfect by a mile, but it should reduce the amount of play to a more reasonable number.



    Follow-up question:
    Are alternate materials for the gib and gib holder a possibility? Our CNC will work with all manner of plastics and non-ferrous metals. We've milled a bit of aluminum on it, and I am willing to try brass as well, but I still need something for the holder (mount? bracket?). Would phenolic or some other type of hard composite be acceptable? My gut says no, but I thought I ought to ask anyhow... I can live with wear, tear, and frequent replacement if it gives me better performance.
     
  2. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    Brass might be an option with the CNC router...

    I am not familiar with those lathes, and there are various types of gibs for carriages. Sometimes metal can be removed from the carriage itself to tighten things up, then fine tuned with the gibs.
     
  3. Kernbigo

    Kernbigo United States Active User Active Member

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    You are over thinking this , i used to rebuild machine. All you have to do is use 24 hr epoxy and put some backing on the original gib, a lot easier than trying to make a new one. I used anything from plastic, metal shim stock or what ever you have that is flat. Try it first and see how muck you need and remember the glue will take up some area. Be sure to clamp it good down to a flat surface, and put some oil pockets on the gib working surface with a hand scraper.
     
  4. Billh50

    Billh50 Active User H-M Supporter-Premium

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    Do you mean the slide has play from the saddle? Or does the whole saddle have play from the bed? My 7x12 didn't have gibs on the saddle only on the slide to saddle. The saddle just has plates that use setscrews and allen screws to adjust.
     
  5. Cavediver

    Cavediver United States Active Member Active Member

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    The saddle has play from the bed. Mine has the same plates, and even though they are tightened all of the way down the saddle is still very, very loose on the bed.
     
  6. Billh50

    Billh50 Active User H-M Supporter-Premium

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    I had the same problem when I got mine. I had to mill a bit off the saddle because even with the setscrews backed out all the way I had play. I measure the bed thickness and then the saddle and found I needed to take .004 off the back and .003 off the front. I just finished measuring another lathe bed for an extension. I was surprised to see the bed rails to be within .0002 of mine. The height is about .006 higher though. But I can mill off the bottom. I will be doing the tapered gib mod though. Since I have it apart and have the material laying around anyway.
     
  7. Billh50

    Billh50 Active User H-M Supporter-Premium

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    As a thought. You could mill a step in the plates to allow them to close up on the bed rail.
     

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