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  1. #21
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    Using levels, test indicators, test bars etc. are good as they can show you exactly where a problem lies. But, the nice thing about the 2 collar test is that it can get your lathe back to work despite those problems, because it gives you the dimensions while the machine is in use.

    I have some well used lathe beds and can get them to turn within .001" over a 12" area. In an extreme case, I could see a bed being so worn that it won't twist back into level cutting, but I'd imagine the wear would be very visible by that point. We also have a Taiwan made engine lathe that I'm constantly having to readjust because the ways are so flimsy, but even there, I can get it cutting straight for a day or two.

    Regrinding the bed and realigning everything is the ultimate fix to make a lathe work how it did on day one, but IMO it shouldn't be absolutely necessary in order to get satisfactory work.

  2. #22
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    Quote Originally Posted by colinag View Post
    When I do the two collar test on a piece of 1 inch 12L14 held in 5C collet using fine feed and a light cut it turns .002 smaller at the head stock than it does 3 inches out.
    Have you found the bed adjustment screw behind the plate at the tailstock end of the bed yet.

  3. #23
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    Again thanks to all. Jim, yes I have loosened the 4 hold down bolts used a long bar held in the chuck stationary with dial indicator at tail stock end, tightened hold down bolts and adjusted both tailstock bed set screws to give 0 deflection. I agree the bed does not have to be level (as aboard ship) just not twisted .I chucked a piece 1.250 bar and did a 2 collar test 8 inches from chuck jaws and got the same 002thou difference over 3 inch length as before with a collet. Just out of frustration I loosened then tweaked the headstock by hand then retightened,When took another cut and found 001 LARGER at headstock this time. Although I can see and feel a ridge just below the top of the veeway perhaps this doesn't matter. When time permits I'll have another try and report results

  4. #24
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    Hello all. After a marathon session of adjust ,cut , measure and tweak I have found that at the headstock with collet I get 002 thou smaller at head end doing a 2 collar test. After loosen -,retighten headstock on bed I get 0-0 on a two collar test 10 inches out from chuck over the same 3 inch spacing between collars. this tells me that the bed is worn to the point that the carriage falls into a hole at the headstock and needs to be reground. Is it worth doing?

  5. #25
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    Are you using the tail Stock?

    A pic of your set up might clear things up.

  6. #26
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    Quote Originally Posted by colinag View Post
    Hello all. After a marathon session of adjust ,cut , measure and tweak I have found that at the headstock with collet I get 002 thou smaller at head end doing a 2 collar test. After loosen -,retighten headstock on bed I get 0-0 on a two collar test 10 inches out from chuck over the same 3 inch spacing between collars. this tells me that the bed is worn to the point that the carriage falls into a hole at the headstock and needs to be reground. Is it worth doing?
    I think you have to answer that question for yourself. What kind of parts do you do? What percentage of them have longish sections with tighter than .002" tolerances on diameter? Do you mind working around a machine tool's shortcomings or will the fact that the lathe is imperfect keep you up at night?

    I don't say this to be snide but only you can determine if an improvement is worth the time and money it will take. If it were me and I had the time and inclination to learn scraping, I'd do it myself. What I wouldn't do is pay someone else to do it as the improvement wouldn't be worth the money to me.

    Teryk

    Sent from my XT1710-02 using Tapatalk

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  8. #27
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    "adjusted both tailstock bed set screws to give 0 deflection."

    That's not how those work. You use those two screws (front and back, this *is* a cabinet model 10L, right?) in opposition
    to make the two collars be the same size. Doing this is a LOT cheaper than finding somebody to wave the magic
    wand over your lathe.

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  10. #28
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    O.K. Jim ,I'll try that . Makes sense. I don't make many longish parts but have trouble boring straight cylinder barrels and small valves and soon I'll need 18 and 36 . I hope. Thanks


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