fastener torque control

[dzy6l7]

I'm tasked with understanding the best methods for achieving fastener torque control and would welcome any inputs. I have a few control processes that have been considered:
1st. Marking the screw head & the use of a dial wrench. 2nd. Basic error proofing verifiers that connect directly to the torque driver.
3rd. Inline transducer connected to a torque analyzer

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[Drazen]

Measuring the lenght of tightened fastener is classic method of quality control. Calculation for lenght vs. specific torque can be found i.e. in Machinery Handbook

 

[plasgears]

Start with lubed fasteners to minimize variation. It could be wax, oil, moly, zinc, black oxide, etc.

Now, when you turn the nut or bolt head, determine how much turn translates to limit stress in the bolt before elastic deformation. Using a torque wrench you can see when stress is entering the plastic region; the torque wrench moves without proportional increase in torque. Run a sample lot, and determine some lower torque level that remains just below the plastic region.

 

[dvd]

Look into getting one of these:

http://www.skidmore-wilhelm.com/products/m_110_2.asp

 

[jsummerfield]

Are you familiar with hydraulic bolt tensioning?

John