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Thread: Remind me again....

  1. #1
    Join Date
    Feb 2012
    St. Catharines, Ontario, Canada

    Remind me again....

    I know I've read or heard this somewhere, but what is the reason the chuck jaws must match the number on the chuck to the number on the jaws? Surely the jaws are made on the same assembly line, and since they can be bought separately it cannot be a matter of being matched to a specific chuck. So what is it?

    The other member of Mensa, but not the NRA

    Everyone is a self-made person.

    "The thing about quotes on the internet is that you cannot confirm their veracity" -Abraham Lincoln

  2. #2
    Join Date
    Oct 2009
    Harrisburg, NC
    I pondered the same thing a few years ago. The only thing I could come up with is that the jaw profile is turned from the billet then sliced apart.
    If it is off a tad when slicing it does not matter as long as they stay in the same order.

    Consider a crosscut on your radial arm saw. It should be 90* but if it is off 2* (one side 88* and the other 92*) it does not matter if you were mating the two ends, it would be amplified if the pieces were not kept in order.

    Keeping the jaws in order keeps it in a true circle even if the cut is a little off. The initial turning is to fit any chuck.

    Just my hypothesis.

    I assume you are talking about buying different jaws set, not an individual jaw (such as a new #4 jaw for 35mm spigots).
    All tyranny needs to gain a foothold is for people of good conscience to remain silent. Thomas Jefferson

  3. #3
    Join Date
    Dec 2006
    Independence, Kentucky
    It's not the Jaws, it's the pieces that the jaws bolt onto that have to be in the properly numbered location, this is so the threads work to move the jaws in and out evenly. Think sort of like cross threading a nut Well, that's not exactly right but hope you get the idea. If you remove the pieces that the jaws bolt on to you will see that the threads are in different locations on the back of them, and it will be pretty self explanatory why they have to be in order, Hope this helps.
    I'm supposed to respect my elders, but its getting harder and harder for me to find one now.

  4. #4
    Join Date
    Oct 2009
    Harrisburg, NC
    Charles is correct. The jaw slides do have to be in the proper order. On Novas (at least older chucks) there is a set screw to limit the amount of expansion and it must match particular jaws which engage it.

    I do think the jaw numbers are still important, at least with Nova. I purchased a Supernova (not a SN2) on the bay that only one other person even bid on because the seller stated it had too much run-out. Resetting the insert properly and placing the jaws in the proper place (every one was in the wrong place) it fell in Novas specs of .005 or less run-out.
    Last edited by Mike Mills; 08-23-2015 at 11:06 AM.
    All tyranny needs to gain a foothold is for people of good conscience to remain silent. Thomas Jefferson

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