Proper torque on lathe chuck jaws

Jay Fleming · Jan 11, 2019

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 :icon_bs:

. 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.

ARB · Jan 11, 2019

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.

Limy Sami · Jan 11, 2019

ARB said:
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 :eek:

) 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

Jay Fleming · Jan 11, 2019

Limy Sami said:
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

Bluejeep · Jan 11, 2019

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

Limy Sami · Jan 11, 2019

Jay Fleming said:
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.

TDegenhart · Jan 11, 2019

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

Tom

npolanosky · Jan 11, 2019

https://www.holo-krome.com/uploads/7/2/7/5/72754089/hk_torquedatachart.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/inc/data/PDF/manu_B-200_BT200_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! :eek:

Zamfir · Oct 2, 2022

This was handy! 80ft lbs it is..That is what I just used on the M12 for the rear adapter plate on the old Howa 10". Now I need to try and thread that bastard back onto the draw tube. OMG. That will be fun even with a ratchet strap holding the chuck up close. Damn things are heavy. No money right now for a new chuck so I cleaned this sloppy sucker up and stoned everything off and its going back in.

Garwood · Oct 2, 2022

Zamfir said:
This was handy! 80ft lbs it is..That is what I just used on the M12 for the rear adapter plate on the old Howa 10". Now I need to try and thread that bastard back onto the draw tube. OMG. That will be fun even with a ratchet strap holding the chuck up close. Damn things are heavy. No money right now for a new chuck so I cleaned this sloppy sucker up and stoned everything off and its going back in.

Did you disassemble it and clean the innards? It sure looks nasty inside. They get real nasty inside, but I've never had one that didn't look respectable after a good disassemble and douche.

Zamfir · Oct 2, 2022

Ohh God yes. It was a mess. I probably need to replace it but can't afford it right now. At least it is clean and greased and ready to attempt to put it back on.

Zamfir · Oct 2, 2022

I did not take the Dratube threaded section off the center but everything else. https://www.practicalmachinist.com/...s-what-to-replace-it-with.406482/post-3981732

doug925 · Oct 5, 2022

ARB said:
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.

Okay, mine is technically set for 86ft/lb for my M12's
lol
But I ALWAYS use a torque wrench and 2" adjustable wrench to hold the jaw when tightening.

Doug.

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Proper torque on lathe chuck jaws

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Bluejeep

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TDegenhart

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Garwood

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