Torque Values...
(Torque Value Guide)

What does Torque vs. Tension Really Mean?
 

This guide to calculate torque values should only be considered as a guide.  Valley Forge & Bolt Manufacturing shall not be held accountable to the use of this guide.  For critical joints further development and studies must be conducted prior to attaining a given torque value.  For assistance with Torque Values please contact us at:

(602) 269-5748.

The alternative to critical joint torque requirement is the use of our load indicating fasteners (MaxBolt^TM or SPC4^TM).  This will eliminate the uncertainty of Torque.

The mystery of torque vs. tension has always intrigued the engineers that have tried to apply this method of tightening on fastened assemblies.  The engineers would have to take into consideration the condition of the fastener, are the fasteners rusty, clean or lubricated, will the fastener require lubrication prior to installation?  These are a few of the problems that engineers must be faced with when a critical joint is encountered. 

How does torque relate to tension?  The biggest factor is “K” which is the coefficient of friction of a fastened assembly.  Below are a few examples depicting a rusty, plain and lubricated fastened assembly.  These are calculated values.

 

Mating Parts		K
	Dry; clean with thin film of oil	0.15/0.20
	Additional lubricating coatings of oil, wax, or dissimilar plating or hard washer	0.10/0.15
	Thread and head bearing surfaces covered with high-performance lubricants or with anti-seize compound.	can be as low as 0.05
	Combinations of certain materials such as Austenite stainless steel screw, bolts And parts not lubricated or coated.	can be as high as 0.35

Torque Calculation Formula	Lubed Assembly:	T=(.05 x .75 x 30,000 lbs.) / 12
T=(k x d x P) / 12		T=93.75 ft./lbs.
	Plain & Clean Assembly:	T=(.15 x .75 x 30,000 lbs.) / 12
T=Torque (ft./lbs.)		T=281.25 ft./lbs.
d=nominal dia. (in.)	Rusty Assembly:	T=(.45 x .75 x 30,000 lbs.) / 12
P=Tension (lbs.)		T=843.75 ft./lbs.