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 spindle which is probed with  the CMM.

Precision JO-PLUGS®  provide positive  results with repeatability and reproducibility  to satisfied customers in the most discerning Quality Labs in the world. Used in conjunction with a CMM or Laser Tracker,  basic position and orientation are quickly and accurately  established.

There are  other methods of determining true position  which  do not reference the pitch cylinder in accordance to ANSI Y14.5 - 2009.

JO-PLUGS®  eliminate the time-consuming task of  probing an internal thread major diameter,  which creates a cone, but does not reference the pitch cylinder.   Probing the  coaxial JO-PLUG® spindle will not damage a stylus  on sharp edges as is the case with internal thread major diameter probing.

Hole location gauges with flexible threads are calibrated before the threads are split. These threads are made to expand  and rest on the thread flanks.  This style is subject to material fatigue,  v-shape, breakage  and  tends to collect chips . 



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 counter bores,  tapered pitch diameter for irregular surfaces, and other particular customer requirements.

 Three easy ways to order:

  • Shop online now using our secure site 
  • Call (586) 758-3800 to order by phone 
  • Call or e-mail to set up an account

- C of C  traceable to ISO/IEC 17025:2005 at no charge with every order

- Fast delivery: Unified, Metric and Heli-Coil®  series threads

-Quick turn-around on custom JO-PLUGS®


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. 

Contact us or Request a Quotation

Spence Industries, Inc.

23888 Dequindre - Warren, MI 48091-1823

(586) 758-3800