Measuring Screw torque

[J2tech]

Can someone please explain the best way to measure torque of a screw. How much does torque driver speed influence/ vary screw torque resulting from use of higher vs. lower speed(from torque driver power source) where torque driver is set to 6lb/in^2 (as example)? If margin error is 5% for a torque driver, is it possible to measure 3-5x the margin error?

 

[CoryPad]

The best way to measure the torque applied to a screw is with an inline rotary torque transducer, such as this one:

http://www.rstechltd.com/rotary_torque_sensors.htm

However, this type of product is more for research work.

For daily measurement, it is best to use a power tool with an integral torque transducer, such as those provided by power tool suppliers like Bosch, Aimco, and Atlas Copco.

Power tool rotation speed influences applied torque only because of variation in the shutoff mechanism (stall, clutch, electric shutoff).

Your units are incorrect - lb/in² is a stress, while lb[·]in is a torque.

I would contact one of the power tool suppliers and have them provide you with a product to meet your needs. This is standard equipment that won't require anything new.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[J2tech]

How accurate will measurement be if torque is measured by measuring break torque (CCW direction) vs measuring displacement of screw by carefully turning torque gage in Clockwise direction? For manufacturing quality purpose which one is repeatable and acccurate? I am thinking of purchasing mark-10 BGI torque gage, any comment on this tools or recommendations. Torque range to be measured is between 2.5 in-lbs to 50 in-lbs.

 

[CoryPad]

Loosening torque is different than tightening torque because the thread pitch torque is not bi-directional. Usually, torque is measured in the tightening direction. This tool appears acceptable. Good luck.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.