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Novel way to center work in a 4jaw chuck.

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  • eKretz
    replied
    Yes, sorry, didn't get the first notification. The diameter needs to be true in terms of cylindrical and not cone shaped (tapered) or turned (or spidered) such that it's running true at the steady location. For example if you had a perfectly straight test piece and placed it in the lathe, with the steady set so the rollers were on center for the diameter of the test piece and the chuck end was offset with a 4-jaw such that it was running eccentric by .250" and the tailstock center was in the other end, the part of the shaft aligned with the steady rollers would be way out of whack and would need to be either turned straight there or a spider would need to be placed on the shaft and set to run true.

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  • dian
    replied
    Originally posted by eKretz View Post

    No it won't necessarily. You can have the stock running out as much as you want at the chuck while the other end is in a steady with zero consequence to the part coming out. The important bit is that the steady is set correctly on center or slightly above, and that the diameter the rest is running on is true to the axis of rotation - that can be accomplished by cutting a spot or running a spider.
    are you there?

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  • dian
    replied
    can you explain that a bit more? diameter true to z-axis?

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  • eKretz
    replied
    Originally posted by BtoVin83 View Post
    Just a 13x40 lathe. Used a steady rest on the tail stock end. When using stock in the steady rest if it is not running purty true the stock will work it's way out of the chuck
    No it won't necessarily. You can have the stock running out as much as you want at the chuck while the other end is in a steady with zero consequence to the part coming out. The important bit is that the steady is set correctly on center or slightly above, and that the diameter the rest is running on is true to the axis of rotation - that can be accomplished by cutting a spot or running a spider.

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  • BtoVin83
    replied
    Just a 13x40 lathe. Used a steady rest on the tail stock end. When using stock in the steady rest if it is not running purty true the stock will work it's way out of the chuck

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  • brian Rupnow
    replied
    My thoughts exactly. Stock doesn't have to be centered to be faced.--Although with doing 2" square tube, the center bore of the spindle must be enormous if I am thinking correctly of your set-up.---Brian

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  • rogee07
    replied


    It seems like a lathe big enough to hold a 36" bar at the head stock, and not need to support the end in the tail stock, would be much bigger than most home shop machinists would have. If you are holding the far end in the tail stock then it doesn't seem like such a big deal. I still find your fathers idea on adjusting a 4 jaw interesting.

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  • oxford
    replied
    If facing off square or rectangular tube, does it really matter if it is in center or not?

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  • BtoVin83
    replied
    Brian it sounds like you are pretty much set on your method but how do you handle square stock or rectangular stock, especially tubing. I had to face to length some 36" long 2" square tubes. Using the method of marking the jaw screws I didn't even bother to dial indicate the chuck end as usually it will be under .010" TIR. Clue me in as I'm open to a better way.

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  • Bented
    replied
    Give it time.

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  • old mart
    replied
    Theres something wrong with this thread, most of the replies are connected with the original theme.

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  • Bented
    replied
    Do it everyday for years on end and it becomes fast, simple and utterly boring (no pun intended).



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  • rogee07
    replied
    As soon as we have a warm day in my garage, I want measure how far a jaw will advance or retard With one turn of the adjustment screw. If the jaw movement is in even numbers, you could move to any size, from a fixed starting possition by calculating the number of turns to get the measurement you want.

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  • BtoVin83
    replied
    It's like follow the dots once you get used to it.

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  • rogee07
    replied
    Now, something different, from a new member. I'll bet this idea could lead to other ways of adjusting a 4 jaw, that most of us never thought about. Since this idea came from Btovin83 father, this could have been a popular way of getting the job done in the past.

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