dynamic torque spec and residual torque spec 1

[clampload]

can anyone please explain me the perfect difference between these two.for example if an automobile plant engineer had changed the dynamic torque spec from 3(min)-4(target)-5(max) NM to 5-6-7 NM saying that torque range is too tight. what does that mean. how will he calculate the min and max dynamic torque spec.

 

[CoryPad]

Dynamic torque spec. would be the actual measured torque during initial assembly of the joint.

Residual torque spec. would be the measured torque during an audit of a joint that has already been assembled. At the automobile manunufacturer where I used to work, it was defined as the torque to move a at-rest, previously tightened fastener in the tightening direction less than 5 degrees.

Regards,

Cory

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

 

[Screwman]

Be careful of how much 'trust' you put into that static torque number. Depending on the circumstances of the joint and the fastener design that number may be higher, lower or in rare cases, the same as the dymanic torque number. One thing that is almost always true is that the scatter on the static torque audit results is about 200% of the scatter in the actual applied dynamic torque.
My advice is to use the dynamic torque value, make sure that you drive tools are 'in control' and forget about applying any kind of torque audit to the parts. Trust your process if it is in control.

Dick