Lathe carriage play

  1. BelgiqueB Member

    Messages:
    26
    Location:
    Belgium
    Hi,

    beginner here, old lathe which works ok when turning od or driling out stock, however when turning inside diameter the results are terrible.

    I've noticed there is a bit of play in the carriage (see picture) however i cant find any way to adjust this rotational play, there are no gibs or anything. Is there any way to fix this problem or are the ways/prisma just worn down and is this lathe ready to be scrapped?

    As a test i tightende the gibs in the cross and the top slide completely to eliminate them as the source of the chatter, results were still the same.

    I can rotate the carriage like the arrows ever so slightly, you can also see it move when i engage the drive. I suspect this is the source of the chatter when doing inside turning.

    Schermafbeelding 2020-02-08 om 18.29.48.png

    In the back of the carriage you have these 3 bolts (two from below one from above) but these only clamp the carriage down on the bed, the bolts in the front and back can be tightened maximum, when you then tighten the bolt in the middle you adjust how easily the carriage moves back n forth up until the point it cant move at all.

    20200208_182306.jpg

    In the front of the carriage it's the same deal, there are 4 bolts and 2 metal pieces that clamp the carriage down vertical, but nothing as far as i can see to adjust rotation.

    20200208_182256.jpg

    Thanks, Christof.
     
  2. spencer 427

    spencer 427 Member

    Messages:
    6,402
    uk colchester
    Location:
    uk colchester
    It's most probably worn the v way in the carriage. Its definitely the cause of the chattering. The bolt in the middle is the carriage lock.
     
  3. Richiew Tungsten Sharpener

    Messages:
    796
    Location:
    Teesside, England
    Is your tool sharp? I have a couple of old lathes and have suffered from this before. I'm pretty new to lathes like you. A fresh sharp tool and correct feeds and speed make a lot of difference to how the lathe performs.

    An alternative might be to drill and ream the gear.
     
    fizzy likes this.
  4. Brad93

    Brad93 M J B Engineering

    Messages:
    6,594
    Location:
    Essex
    Nice Swiss type multifix chuck so we can discount that.

    If you’ve tried tightening the gib on the underside of the saddle front and back, can you still rock the saddle? You could have a high spot on the saddle.

    The cross slide and top slide you should be able to lock off.
    Try and rule out one part at the time.
     
    Last edited: Feb 8, 2020
  5. eLuSiVeMiTe

    eLuSiVeMiTe Forum Supporter

    Messages:
    9,939
    Location:
    Bedfordshire England
    Your not rubbing the bottom of the boring bar are you?
     
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  6. MBB Forum Supporter

    Messages:
    832
    Location:
    northumberland
    Does it chatter when cutting outside diameter if not it could be your boring tool or trying to take too big a cut for the lathe. Are the headstock bearings ok check for play if ok then its as previous posts said.
     
  7. Brad93

    Brad93 M J B Engineering

    Messages:
    6,594
    Location:
    Essex
    have you faced a lathe part and checked for runout?

    Put a clock on the spindle and used a bar to check for play?
     
  8. spencer 427

    spencer 427 Member

    Messages:
    6,402
    uk colchester
    Location:
    uk colchester
    If you took the saddle off you will most probably see this. (Pictures below.)
    The v way has slightly worn. It will wear down to a point and then starts to ride on the ridge.
    This will definitely cause the slight rotation your getting. 20190108_094008.jpg 20190108_094025.jpg
     
    slim_boy_fat and Dcal like this.
  9. pressbrake1

    pressbrake1 Forum Supporter

    Messages:
    1,748
    essex england
    I got accused of being a machine snob last time I commented
    There is a way around this
    You modify the saddle to run on different bed side shears
    A trick often used on myfords

    Edit its a vee bed not double shear
    You can hollow the centre of the saddle ways to stop it rocking, dirty but it works
     
    Brad93 likes this.
  10. optima21 Forum Supporter

    Messages:
    2,699
    Location:
    halifax, England
    you might find its the indexible boring bar thats the issue as they quite often have a negative rake angle compared to normal turning operations.

    have you tried a tool with a brazed carbide tip or a hss tip?

    DSC00031.JPG

    if yours is like the ones I have, they are best used in a round holder. the carbide brazed tip has normal rake for steel and the hss tool on the right has no rake, but works well enough for the light machining that I do
     
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  11. Hopefuldave Intergalactic pot-mender

    Messages:
    1,136
    Location:
    The Shed of Danger, surrey, England
    Can you get a feeler gauge in where the bolts pull the carriage onto the bed? I looks like there's no gap there, so tightening the two bottom bolts won't clamp onto the bed - if that's true, a quick fix would be to grind / machine off the mating face a little from one of the two (most easily the clamping bar under the bed) then adjust so the looseness is taken out (but the carriage still moves), measure the remaining gap and fit shims between the carriage and bar to fix the gap at the right size, making sure you don't leave it too tight to move on the un-worn part of the bed.

    back of carriage.jpg

    front of carriage.jpg

    Dave H. (the other one)
     
  12. zx9

    zx9 Member

    Messages:
    3,635
    Location:
    South East London
    @Hopefuldave makes a good point above, but before altering the clamping arrangements see if you can find any original drawings for your lathe or period photos to ascertain how it was originally done.

    The back way on a Drummond is clamped underside of the flat bed, it has a relief in the middle of the clamp to allow the clamp to slightly pivot as it is bolted up so does not use shims. I have edited the photo to show the general idea.

    CaptureLatheWayClamp.JPG

    Where: A is the relief and B is the edge on which the clamp pivots when the bolts are tightened.

    A previous owner had tried to compensate for wear on my lathe by skimming the relief out removing the adjustable nature of the clamp, adding material to the edge of the clamp and restoring the grove fixed that problem.

    I am not saying that is how your lathe was constructed, just that I think you should be certain how it was originally done and reproduce that method of clamping the way.
     
    Dcal likes this.
  13. MBB Forum Supporter

    Messages:
    832
    Location:
    northumberland
    What make and model is the lathe?
     
  14. Pete.

    Pete. Member

    Messages:
    8,655
    Location:
    Kent, UK
    Saddle vee way is worn at either end. Must be pretty bad to make it rotate like that. Saddle off, machine, scrape or way liner. It's a fair bit of work but the result would be worth it.
     
    spencer 427 likes this.
  15. BelgiqueB Member

    Messages:
    26
    Location:
    Belgium
    Thanks for all the tips and replies guys , I'm not going to bother repairing the lathe as it has multiple other minor problems. Time to invest and upgrade to a bigger machine has come! Am on the lookout on the local 2nd hand market, hoping to find one quickly as i have a fair bit of lathe work that needs to be done in the next couple of weeks!

    If anyone knows of a decent lathe for sale within a 3 hour ride from Dover, let me know, I don't mind taking a day off and crossing the channel to pick up a quality lathe. Budget would be around 3500 euros.

    Thanks.
     
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