Torque wrench using adapters?

[pagrunt]

This thread wants me to yell...

cause of all this science being tossed around

 

[Max Headroom]

EXACTLY!!

This is why an extension can affect the torque. The extension is basically a spring. Stress vs. strain - if you have a couple hundred hours of time to kill, then learn what is occurring in the stress vs. strain relation. The relation explains in detail why a TTY bolt cannot be re-used it you want an accurate clamping force.

On the other hand, if you have an extension that requires more torque to twist than you are applying, then it will provide an accurate torque.

Let's try this another way. Take a spiral wound spring (like in a clock) and mount the center of the spring to a shaft and the outer/tail end of the spring to a ring surrounding but not attached to the shaft. The ring is in a groove that limits motion to a circular path. Say it takes 10 ft/lbs of torque to move the ring in the groove. Say it takes 20 ft/lbs of torque to compress the spring to coil bind. If you put a torque wrench on the end of the shaft and turn the wrench to make the outer ring move in the groove, how many ft/lbs of torque will you have to apply before the ring starts to move??

Remember, it will take a constant 20 ft/lbs of torque to get and keep the spring compressed. What will the torque wrench read when the ring starts moving? The wrench should actually click at 10 ft/lbs before the spring is fully compressed. So no movement of the ring.

If there is no flex in the shaft extension (as in the Snap On video), the full force is transferred to the bolt head. If there is flex occurring in the shaft (i.e. the shaft is acting like a spring) at a force less than the torque value then some of the force is taken up flexing the shaft and while the wrench will click at the applied torque setting, not all of that force is applied to the bolt.

Mom said!!