Tool Testing – Skidmore-Wilhelm

Tool Testing

Refers to measuring the performance of fastener installation tools and can be broken down into two different realms.

Direct Torque Measurement

Model W

The Model W was designed to directly measure the torque output of manual torque wrenches within 1% accuracy.  

We cannot recommend using the Model W family for impact tool or pulse tool testing applications. 

The Model W does not require electrical power to operate, instead it is a hydraulic design that uses a lever arm to compress a piston against a column of oil.

The hydraulic pressure is measured using a pressure gage and the gage dial has been calibrated to read in units of TORQUE (N-m or lb-ft). The torque calculation for the gage dial is as follows:

Torque = Hydraulic Pressure x Piston Area x Effective Lever Arm Length

Model T

The Model T is used mainly for impact gun repair shops.

The Model T was designed as a “hard Joint” to directly measure the torque output of impact guns and manual torque wrenches within 1% accuracy. It requires 110/220 V power to operate. It measures torque using a strain gaged torsion beam whose signal is processed and output to a digital readout in units of N-m or lb-ft.

Keep in mind this is measuring the “peak” output torque of the impact gun. It does not take account for any inertial load lost to the mass of the socket and if the socket is loose fitting over the nut. Unlike a torque wrench, which is a static method transferring all the force needed directly to the nut, an impact gun needs to build an inertial load.  

 

We cannot recommend using the Model T for pulse tool testing applications.  You can read more about the reasons for this on our Tool Testing FAQ page.

Approximate Torque/Relative Performance Measurement

Model H

Model J

Model K

Model RL

Model S

These models are designed to directly measure bolt TENSION within 1% accuracy. They do not require electrical power to operate and they can be used with any tightening tools.

These units can be used with our special Test Bolt Assemblies and lubricant to determine torque values Indirectly. These units will NOT measure torque directly.

To do so requires dividing the indicated bolt tension by the “K” factor of the test bolt assembly. 

There is an inherent variation in “K” factor so the accuracy of this computation is a moving target under the best conditions.  We can not recommend calibrating torque wrenches with these tools.We measure the tension that these installation tools are able to generate in the Test Bolts and then divide the Tension by an appropriate "Torque Factor" to arrive at an "approximate" torque number.  

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