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Worm and worm bushing?

Discussion in 'LOGAN ENGINEERING CO. & LOGAN WARDS' started by RonRock, Mar 15, 2017.

  1. RonRock

    RonRock United States Active Member Active Member

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    Sorry but as I reassemble my 1937 I'll have a lot of questions.

    So right now the question is about the worm. What direction should it be installed in? Mine has a key that keys it to the Lead Screw. The key is machined in the worm a bit less than 1/2 the length of the worm. Leaving me to wonder should the key be towards the Headstock or Tailstock when assembled?

    The worm bushings have detents in them to locate the bushings with the set screws. when the bushings and worm are installed the worm has a lot of end play inside the bushings. I assume this is by design, but thought I'd ask. Should there be shims inside the bushings to take up this slack? I didn't measure but the worm slides for and aft probably 1/4 inch or more. Also how tight of a fit should the worm have to the bushings? Mine are showing some wear, but they are steel as is the worm, no oillight bushing to replace. So I'll again assume that a bit of slop in the worm is acceptable. I checked the cost of the worm. Ouch! I could bite the bullet on the bushings if they need to be "tight." But this looseness appears to be designed into the machine.

    Oh one more.

    On the compound and crossfeed dials, under the thumbscrew is supposed to be a "slug." I have 1 and need to replace 1. The 1 that I have looks to be a piece of solid copper maybe brass. I'm thinking copper wire or round stock. That sound right? Or is the "slug" something special so that it don't damage the shaft?
     
  2. wa5cab

    wa5cab Downloads Moderator Staff Member H-M Supporter-Premium

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    I don't know anything about the worm and bushings, although I would guess that 1/4" end float is too much.

    For the dials, you can use brass rod the same diameter as the minor diameter of the female threads. Probably find the rod at a hobby store like Hobby Lobby. Or from McMaster, etc. Cut a piece about one diameter long and drop it in the tapped hole, followed by the thumb screw. Lead also works, although probably harder to find.
     
  3. RonRock

    RonRock United States Active Member Active Member

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    I'll reply with how I resolved this. Just in case someone else can use the help.

    I recently joined the Yahoo group "lathe-list" which is a users group established and moderated by Scott Logan. So should be able to get some pretty solid advice from there. Although I personally don't care for the way Yahoo groups work, much prefer this type forum. But that's beside the point.

    So I posted a similar question there and the reply was that the bushings had been "dimpled" on install. The suggestion was to move the bushings to get the worm to fit tighter and drill new dimples. Easy to do and it took out the end play of the worm. I left mine so that it was a bit loose so that it was not wearing on the bushings excessively.

    I was also told that the direction of the worm did not really matter, it will work either way. But was suggested that I may get a little more travel up close to the headstock if the key in the worm was positioned towards the tailstock. I checked my worm on my leadscrew and found that it would make a slight difference, but followed the advice and installed it with the key towards the tailstock.

    I probably should have replaced the worm and bushings for the best results. But price is a factor of course, it would be real easy to get wayyy too much money in this machine. So I do the best I can with the money I spend on it.

    I do wish that I could fit some oillight bushings inside the OEM bushings, I think that would be a top notch solution for the money. But I only have 1 lathe, and it is in parts!



    The "slug" I made from a piece of copper wire. Brass might be better, but I figured copper would be softer.
     
  4. Chuck K

    Chuck K United States Active User H-M Supporter-Premium

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    The problem with that much play in the worm bushings is all the time wasted waiting for your carriage to move after engaging the feed...lol. Been there. I just got done making worm bushings for

    http://hobby-machinist.com/threads/sb-apron-repair.55753/

    a SB 16. They were pretty well shot. Moving the bushings or making bronze spacers will tighten it up. I haven't priced those parts but I would expect they're pricey. Sometimes you got tone run what you got.
     

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