ANSI Y14.5 – 2009, Dimensioning and Tolerancing, Section 2.9, states that “each tolerance of orientation and datum reference for a screw thread applies to the axis of the thread derived from the pitch cylinder."  The Positional Tolerance Method (Section states that the pitch cylinder is the default condition. The JO-PLUG® solid thread form provides a calibrated pitch diameter, coaxial and concentric to the stem. Compared to other methods, which do not reference the pitch cylinder, Precision JO-PLUGS® are preferred  by blue-chip Quality professionals. 

Precision JO-PLUGS®  provide positive Quality results with repeatability and reproducibility  to  our satisfied customers in a wide range of industries. Used in conjunction with a CMM or Laser Tracker, basic position and orientation are established quickly and accurately. Projected tolerance zones and perpendicularity are also measured.


In addition to off-the-shelf Precision JO-PLUGS®, Spence Industries, Inc. specializes in the manufacture of custom gages for unique applications:   extended projected tolerance zones, tapped holes below counterbores,  tapered pitch diameter threads, and other particular customer requests.

- Certificate of Compliance at no charge with every order

Fast delivery 


Precision JO-PLUG® pitch diameters are calibrated using a Pratt & Whitney Super Mic utilizing  the universal "three wire method."


Precision JO-PLUG®  "lead and trail" thread angles are verified using a J&L Metrology Optical Comparator. 

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Spence Industries, Inc.

23888 Dequindre - Warren, MI 48091-1823

(586) 758-3800