Which method to reduce cross-slide backlash?
Close
Login to Your Account
Page 1 of 2 12 LastLast
Results 1 to 20 of 29
  1. #1
    Join Date
    Sep 2015
    Country
    UNITED STATES
    State/Province
    Florida
    Posts
    619
    Post Thanks / Like
    Likes (Given)
    4
    Likes (Received)
    89

    Default Which method to reduce cross-slide backlash?

    About 1/2 turn (60 thou) backlash on a Sheldon I've just brought "online".
    The screw shows light/reasonable wear on visual inspection, and backlash is about the same even at the far end of travel where there would be zero wear; so the bulk is in the nut.

    Machine a new bronze nut? No acme threading tooling or tap, easily solved. Delrin? Even seen this "melted" around an unworn section of screw after boring to correct ID as alternative to machining.

    Moglice? Perhaps impractical for such a small job (my guess is I'd have to buy far more than needed for such a small job and I'm sure it ain't cheap). But time is money, and the far end of the screw (integral taper attachment) never sees the nut so it is unworn and perfect to "cast".

    I've also heard of using solder inside the nut threads to reduce backlash.

    What's the fastest/easiest route here?

  2. #2
    Join Date
    Jan 2005
    Country
    CANADA
    State/Province
    Saskatchewan
    Posts
    10,236
    Post Thanks / Like
    Likes (Given)
    1394
    Likes (Received)
    3688

    Default

    Check the actual end play of the screw against it's thrust housing. Perhaps a custom shim washer will tighten it up considerably. If you can get it down to .030" I wouldn't bother with trying to reduce it further. I use large manual lathes all day long with .015" to .030" radial backlash, and it doesn't bother me a bit. Mind you, the screws are coarse, so that doesn't amount to a half turn, more like a quarter turn.

    Excessive backlash really only becomes a problem when you're trying to back out quick near a shoulder when threading. Then it is nice to not have to turn it so far to get clear. But you always have to learn to compensate for backlash when running any manual machine with acme screws by making your cutting position with a uni-directional positioning move.

  3. #3
    Join Date
    Sep 2010
    Location
    Oklahoma City, OK
    Posts
    4,471
    Post Thanks / Like
    Likes (Given)
    770
    Likes (Received)
    1848

    Default

    I put a delrin nut in my monarch when I redid the x slide screw years ago. It's easy, it's accurate, but...it sucks for knurling. The high tool pressures and plastic nut make getting a good knurl tedious.

    I can't say that I'd recommend it on a lathe of that size. And one day I'll eventually replace mine with bronze.

    Sent from my SM-T560NU using Tapatalk

  4. Likes Billtodd liked this post
  5. #4
    Join Date
    Jan 2019
    Country
    UNITED STATES
    State/Province
    North Carolina
    Posts
    229
    Post Thanks / Like
    Likes (Given)
    26
    Likes (Received)
    39

    Default

    What thread is your screw and nut? I’ve got quite a few acme taps, I may be able to thread something for you if needed.

    Or if the screw and nut are both worn I’d be happy to make you a replacement.

  6. Likes whidbey liked this post
  7. #5
    Join Date
    Jan 2007
    Location
    s w NH
    Posts
    325
    Post Thanks / Like
    Likes (Given)
    227
    Likes (Received)
    119

    Default

    google anti backlash nut

  8. #6
    Join Date
    Feb 2007
    Location
    St. George, Utah
    Posts
    906
    Post Thanks / Like
    Likes (Given)
    457
    Likes (Received)
    603

    Default

    My Sheldon (1975 EM-70) has a split nut with the ability to adjust for backlash. Have you had yours apart to see if you have it too?

  9. Likes Ray Behner liked this post
  10. #7
    Join Date
    Jan 2015
    Country
    UNITED STATES
    State/Province
    Missouri
    Posts
    1,048
    Post Thanks / Like
    Likes (Given)
    211
    Likes (Received)
    656

    Default

    Could a guy install a gas cylinder off a car a small one to push back against the toolpost to remove the back lash. Kind of like holding back against it with the off hand?


    Sent from my iPhone using Tapatalk Pro

  11. #8
    Join Date
    Jan 2019
    Country
    UNITED STATES
    State/Province
    North Carolina
    Posts
    229
    Post Thanks / Like
    Likes (Given)
    26
    Likes (Received)
    39

    Default

    I suppose you could do that. But with a cylinder causing constant pressure on one side of the thread profile at all times I’d expect some expedited wear. Pressure on the screw during a cut is one thing but pressure on the screw and nut constantly is another. Also depending on the amount of wear the screw has any inaccuracies would be more apparent I would think. IMO. I just make a habit of giving by toolpost a quick tug back towards myself before making my adjustments. But that’s more to do with endplay really, though backlash would cause that as well.

  12. #9
    Join Date
    Sep 2015
    Country
    UNITED STATES
    State/Province
    Florida
    Posts
    619
    Post Thanks / Like
    Likes (Given)
    4
    Likes (Received)
    89

    Default

    Quote Originally Posted by naru View Post
    What thread is your screw and nut? I’ve got quite a few acme taps, I may be able to thread something for you if needed.

    Or if the screw and nut are both worn I’d be happy to make you a replacement.
    1/2"- 8 tpi.

    If there's a tap made for it (not going custom for a one-off), I can't find one.

    I do have an internal threading tool for TNMV "standup" inserts but can't find an acme insert that size.

    Solid carbide cutter runs over $100. Search continues...

  13. #10
    Join Date
    Nov 2017
    Country
    UNITED STATES
    State/Province
    California
    Posts
    288
    Post Thanks / Like
    Likes (Given)
    182
    Likes (Received)
    196

    Default

    How far have you dug into this? My SB Heavy 10L had 140 thou (!) of backlash when I got it. Tightening up the bolt that retains the nut got rid of most of it, replacing the missing thrust bearing eliminated the rest. It now has less than 10 thou. Sometimes it's simpler and easier than it seems.

  14. Likes JST, onecut liked this post
  15. #11
    Join Date
    Jan 2019
    Country
    UNITED STATES
    State/Province
    North Carolina
    Posts
    229
    Post Thanks / Like
    Likes (Given)
    26
    Likes (Received)
    39

    Default

    Quote Originally Posted by tobnpr View Post
    1/2"- 8 tpi.

    If there's a tap made for it (not going custom for a one-off), I can't find one.

    I do have an internal threading tool for TNMV "standup" inserts but can't find an acme insert that size.

    Solid carbide cutter runs over $100. Search continues...
    I may actually have one of those.. if not threadmilling is a viable option. You’d be hard pressed to single point that. The minimum dia. Of that thread must be around .4-.38”.

  16. #12
    Join Date
    Nov 2017
    Country
    UNITED STATES
    State/Province
    California
    Posts
    288
    Post Thanks / Like
    Likes (Given)
    182
    Likes (Received)
    196

  17. #13
    Join Date
    Nov 2004
    Location
    Webster Groves, MO
    Posts
    7,330
    Post Thanks / Like
    Likes (Given)
    1850
    Likes (Received)
    3399

    Default

    These people probably have the original part. If it is not impossibly expensive, pay the price and get the right part.

    Sheldon Lathe OEM Repair Parts by Bourn & Koch

    The Cincinnati cylindrical grinders I work on have a hydraulic cylinder on the cross slide that takes up the play when running. They routinely work to tenths.

    Bill

  18. #14
    Join Date
    Sep 2010
    Location
    Oklahoma City, OK
    Posts
    4,471
    Post Thanks / Like
    Likes (Given)
    770
    Likes (Received)
    1848

    Default

    Quote Originally Posted by MrWhoopee View Post
    This ^^^^^ is definitely the way to go.

  19. #15
    Join Date
    Sep 2004
    Location
    Rugeley UK
    Posts
    1,016
    Post Thanks / Like
    Likes (Given)
    23
    Likes (Received)
    108

    Default

    Want a crude, low tec, nothing to loose type solution? Then get the nut in a vice and very carefully squeeze it until it is just right on the screw.
    I know it's crude but but it works rather well!

  20. #16
    Join Date
    Feb 2007
    Location
    St. George, Utah
    Posts
    906
    Post Thanks / Like
    Likes (Given)
    457
    Likes (Received)
    603

    Default

    Quote Originally Posted by 9100 View Post
    These people probably have the original part. If it is not impossibly expensive. . .

    Bill
    Just to prepare anyone going this route, last month I asked them about a replacement fwd tumbler gear: one fiber gear and the associated bushing. The quote? $975! Yup, no typo. Nine hundred and seventy-five dollars for a 2" formica gear and a bushing. Unbelievable. I used a $30 standard from Boston Gear instead.

  21. Likes MrWhoopee liked this post
  22. #17
    Join Date
    Jan 2007
    Location
    Flushing/Flint, Michigan
    Posts
    7,962
    Post Thanks / Like
    Likes (Given)
    402
    Likes (Received)
    6590

    Default

    Why?
    You cut inwards not outwards.
    You need to face groove to a certain spot , go into it.
    There will always be some lash so is .003 better than a 10 or 30 times bunch?
    Maybe some could speak to .002 lash vs .060.
    Bob

  23. #18
    Join Date
    Feb 2007
    Location
    St. George, Utah
    Posts
    906
    Post Thanks / Like
    Likes (Given)
    457
    Likes (Received)
    603

    Default

    Generally right, Bob, but it does get annoying if backlash is excessive. Any more than my wrist will turn without changing grip is too much, or even less than that when backing off a tight bore. You know... is it clear yet? etc.

  24. #19
    Join Date
    Nov 2017
    Country
    UNITED STATES
    State/Province
    California
    Posts
    288
    Post Thanks / Like
    Likes (Given)
    182
    Likes (Received)
    196

    Default

    Quote Originally Posted by CarbideBob View Post
    Why?
    You cut inwards not outwards.
    You need to face groove to a certain spot , go into it.
    There will always be some lash so is .003 better than a 10 or 30 times bunch?
    Maybe some could speak to .002 lash vs .060.
    Bob
    Backlash is just generally at odds with the perfectionist nature of machinists. It is sloppiness that exceeds our level of psychological tolerance, which is in the tenths. The minimum amount of backlash on a lathe is barely tolerable. The fact that quality, precision work is possible with backlash in the .06 range is irrelevant. It upsets our mental balance like a window out of plumb.

  25. #20
    Join Date
    Sep 2011
    Country
    UNITED STATES
    State/Province
    Virginia
    Posts
    27,661
    Post Thanks / Like
    Likes (Given)
    7561
    Likes (Received)
    8611

    Default

    Quote Originally Posted by Cole2534 View Post
    I put a delrin nut in my monarch when I redid the x slide screw years ago. It's easy, it's accurate, but...it sucks for knurling. The high tool pressures and plastic nut make getting a good knurl tedious.

    I can't say that I'd recommend it on a lathe of that size. And one day I'll eventually replace mine with bronze.
    THANK YOU! ....for that ration of honesty off the back of actual field experience.

    "Some folks" were of the opinion that Delrin was actually all-around BETTER than bronze. Neither are perfect, of course, but still.

    There ARE sources for bronze nuts to modify, and one can also then split them or pair them for backlash adjustment.

    Not as if a body was likely to have to do this TWICE, any given machine-tool, what with how long the originals lasted in what was probably more severe service and greater neglect than we ever-so attentive chikn's plan to lavish on our toys, going forward. Or - realistically - just use them less-often?



Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •