Tailstock bit low

  1. fizzy Member

    Messages:
    6,357
    uk
    I don't know if this is the right way to test. Centre point punch held in a collet and a dead centre in the tailstock. Tailstock is a fraction low. Seems ok side to side.
    How do I correct this?

    20200720_192351.jpg

    20200720_192428.jpg
     
  2. fizzy Member

    Messages:
    6,357
    uk
    Samsung cameras are amazing! And look at the way the light reflects giving a clear line between the 2 parts.
     
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  3. eLuSiVeMiTe

    eLuSiVeMiTe Member

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    12,071
    Location:
    Bedfordshire England
    Probably worn bed near the Chuck
    Turn up a test bar and check.

    Any adjustments on the TS
     
  4. fizzy Member

    Messages:
    6,357
    uk
    Side to side only I think?
    When you say a test bar do you mean between centres?
     
  5. Shox Dr

    Shox Dr Chief Engineer to Carlos Fandango

    Messages:
    15,459
    Location:
    East Yorkshire
    There (usually) only side to side adjustment on a tailstock. My m300 tailstock was not only worn on the base it was bell mouthed as well. The base error was taken out by scraping; it was 17thou in one corner, less in the others.

    once Id built up the lathe I had to bore out the tailstock and sleeve it. Good as new now, but took some work to put it right.

    Linky to thread https://www.mig-welding.co.uk/forum/threads/m300-tailstock-refurb-boring-and-sleeve.39064/
     
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  6. nickk Forum Supporter

    Messages:
    2,387
    Location:
    Hay-on-wye
    You could place some shims under the T/S to lift it.
     
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  7. Seadog

    Seadog Forum Supporter

    Messages:
    6,453
    Location:
    NE London - UK

    Between the base and the upper part, so at the sliding joint used to adjust offset.
     
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  8. Shox Dr

    Shox Dr Chief Engineer to Carlos Fandango

    Messages:
    15,459
    Location:
    East Yorkshire
    Its a huge bodge. The tailstock base is likely worn, as will be the bed. Where do you take your measurements from to get it on centre? As soon as you move it the error will change.


    Edit; sounds like Im having a go at you @Seadog.:hug::hug:. Im not:thumbup:
     
    Last edited: Jul 22, 2020
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  9. minimutly Member

    Messages:
    1,215
    Location:
    Pembrokeshire Wales
    Agree, and the wear in the bed is likely more than the wear in the tailstock. And unless you're machining small diameter long stuff it won't make that much difference anyway. And if you are machining small diameter long stuff you should do a test cut to correct any errors with the tailstock. Ok, this is a fix that won't be a guaranteed fix due to non linear errors, but it could help.
    Please accept that this is a teach yourself machinists opinion, not a time served turner's.
     
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  10. fizzy Member

    Messages:
    6,357
    uk
    I think I have worked out a way to measure it. I have a vernier height gauge. I could use some parallels on the ways and check it at various points along the bed.
    Is that a plan?
     
  11. Bullet2012

    Bullet2012 Forum Supporter

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    1,451
    Location:
    Berks
    no idea ask Balderic :hug::scared: sorry
     
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  12. Pete.

    Pete. Member

    Messages:
    9,407
    Location:
    Kent, UK
    The proper way to measure it is to put something in the chuck and turn it down to the diameter of the tailstock. ~Then bring the tailstock up to the part and mount a dial gauge on the carriage. Use the carriage to run the dial gauge from one to the other. The difference is how low you are, shim to suit.

    Really though the vertical offset has very little effect on the part produced unless the part is very small in diameter. Side to side offset has a huge effect mind.
     
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  13. fizzy Member

    Messages:
    6,357
    uk
    I suspect I am expecting a bit too much from a 55 year old lathe.
    All this thousands of an inch nonsense I expect it to be bang on :laughing:
     
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  14. graffian

    graffian Seer unto the end of his beard

    Messages:
    3,007
    Location:
    gatwick
    If you want to know where the tailstock bore is in relation to the spindle,
    stick a dial gauge in the chuck and rotate it in the tailstock bore.
     
  15. Steveblade

    Steveblade Member

    Messages:
    133
    Location:
    West midlands
    Yeah thats the correct method as Graffian said, thats how you dial in the turret on a cnc lathe. Error in the tail stock is error makes no difference if its centre hight error or left right its an error. The longer a drill is , mounted in the tail stock, the further it will be off centre. Why do you think you keep your drills (and tools short) in general ?

    Good question though I could use the answer to for a Harrison lathe, Id guess the tail stock and ways are knackered to be fair.
     
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  16. pressbrake1

    pressbrake1 Forum Supporter

    Messages:
    2,522
    essex england
    Shim it. The front of the tailstock sled / base wears.
    It’s not a bodge it’s a non invasive way of sorting it and opening a can of worms.

    Put a clock reading to of quill and slide tailstock with quill fully extended to measure droop

    If you look underneath the tailstock base where in runs on the bed wear will be visible. The bed certainly doesn’t wear worse than the tailstock
     
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  17. pressbrake1

    pressbrake1 Forum Supporter

    Messages:
    2,522
    essex england
    As Pete says for general work being slightly low isn’t a problem unless you want a reamer to cut to size
     
  18. Pete.

    Pete. Member

    Messages:
    9,407
    Location:
    Kent, UK

    You have to be very careful doing this. If you mount the dial gauge on a rod and rotate the chuck the rod will bend under the weight of the gauge (and itself) and mess up your readings,

    Put a mag base on a small surface plate, zero the gauge then turn the plate over, you'll see the gauge has moved 5-10 thou probably.
     
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  19. graffian

    graffian Seer unto the end of his beard

    Messages:
    3,007
    Location:
    gatwick
    I use a dial indicator bolted to a bit of bar. It seems to work OK.

    tailstock-centre1.jpg
     
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  20. Pete.

    Pete. Member

    Messages:
    9,407
    Location:
    Kent, UK
    It would do, but you'll never know how much the bar bends under it's own weight using that setup. Won't be much with a bar that chunky but it WILL be bending.
     
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