How strong is a 10 mm Hex Key ?

[awemawson]

Today I re-aligned the tool disk on the turret of my CNC lathe, which involved unscrewing eight  10 mm socket cap screws with a 10 mm hex key.

They were so tight, it wasn't until I added a four foot long tube as a 'torque amplifier' and my not inconsiderable mass that things started to move.

I must have been very close to the shear strength of the key. it was a good quality 'Unbrako' one, but what sort of torque will they take before bits go flying and knuckles get bruised ?

[awemawson]

quick correction - those cap screw were 12 MM !!!!!

[TomG]

Good question Andrew. There are torque ratings for the cap screws themselves around 160 foot pounds for a 1/2" screw, but not much on the key itself, and those ratings are for the working strength, not ultimate strength. I suspect the screw itself would fail before the hex key.

Tom