Proper torque on lathe chuck jaws
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    Default Proper torque on lathe chuck jaws

    Our 12" Bison has no documentation but it's a Kitagawa-interchangeable model, so I looked at the Kitagawa B212 manual. It says the M16 jaw bolts require 185 ft-lbs (250 N-m technically). It felt like it took 500 ft-lbs to break them free . After adjusting them, I retightened with a 1/2" breaker bar and one or two grunts, so probably in the 100 ft lb range. This is on a brand new lathe, new chuck, new jaws, etc. What's reasonable for tightening them back? Mfr spec or something a bit more reasonable.

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    I've taken to using a torque wrench tightening chuck jaws and mount bolts. The M12 get 84 LB-FT on my lathe. Other than piece of mind it does seem to increase consistency when remounting soft jaws.

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    Quote Originally Posted by ARB View Post
    I've taken to using a torque wrench tightening chuck jaws and mount bolts. The M12 get 84 LB-FT on my lathe. Other than piece of mind it does seem to increase consistency when remounting soft jaws.
    Having seen a chuck jaw come loose - because it was never tightened properly, at high RPM and throwing a large part in the process, (which only just missed a very young and green Sami ) I have always been very very careful over such procedures??


    As for the OP's 185 ft lbs, IMO is not over tight for an M16 Allen Bolt

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    Quote Originally Posted by Limy Sami View Post
    Having seen a chuck jaw come loose - because it was never tightened properly, at high RPM and throwing a large part in the process, (which only just missed a very young and green Sami ) I have always been very very careful over such procedures??


    As for the OP's 185 ft lbs, IMO is not over tight for an M16 Allen Bolt
    Over tight wasn't the question necessarily, but necessarily tight.

    I'll get a 1/2" torque wrench and go to work.

    Sent from my SM-G960U using Tapatalk

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    I torque my jaws using a 80lb torque stick on an air impact.

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    Quote Originally Posted by Jay Fleming View Post
    Over tight wasn't the question necessarily, but necessarily tight.

    I'll get a 1/2" torque wrench and go to work.

    Sent from my SM-G960U using Tapatalk
    I think something may have got bit lost in the translation Jay, ….to us Brits if somethings ''not over'' - it's about right.

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    In situations like this, my advice is "tight as you can get it, then two full turns more".

    Tom

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    https://www.holo-krome.com/uploads/7...edatachart.pdf

    These guys who make bolts say M12 should be about 120ft-lb and M16 should be 300ft-lb

    Torque Information : Fuller Fasteners

    These other guys who make bolts give figures about 20% lower for high grade hardware.

    http://www.kitagawa.com/en/mtools/in...00_v107_en.pdf

    And finally, kitagawa gives 79 ft-lb for M12 and 184ft-lb for M16.

    So it sounds like it's up to you, but kitagawa's numbers are probably safe enough and holo-krome is probably pushing the limits. Throw another ugga-dugga on it and call it good enough, just stand out of the plane of rotation!


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