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[How do I?] Measuring Lathe way wear

Discussion in 'QUESTIONS & ANSWERS (Get Help Fast Here!)' started by lindse34, Oct 30, 2012.

  1. lindse34

    lindse34 Active User Active Member

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    Greetings Everyone,

    I recently picked up a 17" Leblond lathe of mid 50's vintage. From what I can tell so far its an OK machine. I am wanting to measure the wear on the ways and from searching around it sounds like a somewhat difficult task without good instrumentation. I am hoping to do a little better than a straightedge and using the optical comparator I was born with. So my question is if I chucked a ground drive shaft (45mm) and held it with the tail stock, would running an indicator across it tell me anything useful?

    Thanks,

    Matt

    PS,

    This seems like quite the nice group on here.
     
  2. Chazz

    Chazz Active User Active Member

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  3. 4gsr

    4gsr Global Moderator Staff Member Supporter Active Member Director

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    The simplest and easyist check for wear is to chuck up a piece of bar or heavy wall tube about 3" OD with about 6-8" sticking out of the chuck. I suggest using a 4-jaw chuck so you can get a good "grip" on the bar. Sprung jaws on a 3-jaw could give you a false sense of measurement. Take a decent cut to get a good fresh OD exposed. The take a .010" depth of cut with a positive rake tool, perferrable high speed steel with a honed sharp edge to the cutting tool. Take mic measurments at different locations on the length of the bar. Record measurements. Rotate the chuck 90 deg. again take measurments and record.
    Compare measurements for any taper or out of round in the turned bar.
     
  4. 4gsr

    4gsr Global Moderator Staff Member Supporter Active Member Director

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    The later LeBlond lathes built with the funky ways on it are notorious for wearing on the front short height almost vertical way.

    LeBlond's theory behind this design was the cutting forces are directed to the wide almost flat front way and the short height almost vertical way was the one that guided the carriage up and down the bed. I think their engineers missed calculated the vector forces involved.
     
  5. lindse34

    lindse34 Active User Active Member

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    I see what you mean about the odd front way. Thanks for the tip. I'll be digging through the cut off pile and see if I can find a 3"ish bar stock.
     
  6. Chazz

    Chazz Active User Active Member

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    @ 4GSR, not to start an argument, but IMHO, I thought your method will check the axial relationship between the headstock & the ways, not actual way wear?

    I'll try to find the thread that some chap posted to show how he check the ways and it was quite a lot more involved.

    Cheers,
    Chazz
     
  7. lindse34

    lindse34 Active User Active Member

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    I may be wrong, but if the center line the work piece is rotating about is not axial to the ways there should be taper that is consistent along the workpiece. If the taper is not linear that would indicate some amount of wear on the ways. Now sorting out the difference between the two may be very difficult or impossible? I will be ordering the machine tool reconditioning book I think.
     
  8. 4gsr

    4gsr Global Moderator Staff Member Supporter Active Member Director

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    Chazz,

    My basic method will detect some wear. It's not a proper method to use, but more of a "quick and dirty" way of determining that wear does exists.

    I can go into great detail of other ways to use to detect wear, but I would be here for a few days writing.

    Connelys book has a couple of good ways to check for wear, but when it really comes down to it. Put the lathe bed up on a planer align up and probably get the closet measurments than any other method out there provided the planer is accuract.
     
  9. 4gsr

    4gsr Global Moderator Staff Member Supporter Active Member Director

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    Lindse, you are on the right track. Basically putting a piece of material between centers and turning the OD from end to end and checking for taper. Sometimes you can do this and adjust some of the taper out by setting over the tailstock by a matter of a few thousands. The variation in the OD that will not adjust out would be a indication of wear in the bed. Still won't know how much.
     
  10. Chazz

    Chazz Active User Active Member

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    I'm just thinking that I may get a false positive because of tool deflection on my little guy.

    Actually, your "optical comparator" and "straight edge" arn't such a bad idea (I think:thinking:) If you have removed the bed before, or are comfortable doing it, along with the tail stock. Blue it up, get a 18"~24"+ Precision ground straight edge, give it a rub and use your comparator.

    Cheers,
    Chazz
     

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