What is the Common Centerline? 

Georgia State University says this about torque:   "Note that the torque is maximum when the angle is 90 degrees. A practical way to calculate the magnitude of the torque is to first determine the lever arm and then multiply it by the applied force. The lever arm is the perpendicular distance from the axis of rotation to the line of action of the force."

Apply the same force to a different length lever arm and the torque output changes. The length of the lever arm includes the area on the head up to the center of the fastener. 

Common Centerline for interchangeable heads on industrial assembly tools

The common centerline is measured from the center of the fastener to the top of the dovetail. 

Why Is Common Centerline Important?

Due to physical size constraints, Sturtevant Richmont interchangeable heads have two common centerlines. Typically for sizes 32 mm and below the common centerline is 36.5 mm. Sizes larger than 33 mm the common centerline extends to 98.4 mm.

If your application requires a preset wrench with a 60 mm open-end head, it can be difficult to attach the head of the wrench to your tester. Our 3/4 ratchet and solid square drive have the same common centerline as our 60 mm open end. By switching to the 3/4 drive, calibration is now possible.

Our CCM micrometer adjustable wrenches are calibrated with either the 36.5 mm common centerline or the 98.4 mm common centerline. 

Be sure that the interchangeable heads you buy are accurate, reliable, and durable.  

Go To Interchangeable Heads.


Sturtevant Richmont tools are made in America

Sturtevant Richmont tools are proudly made in Carol Stream, Illinois by highly capable and hard-working hands.