You can check both pitch diameter and taper on a rotary shouldered connection with the same gage. After using a PD-8000-RSC gage to inspect PD, zero the gage on the part. Then, just like using a taper gage, move one inch down the thread and inspect taper. Before moving to the next inspection, be sure to reset the gage on a setting standard.

When comparing a Functional Diameter measurement to a Pitch Diameter measurement, the difference between the two readings should not exceed 40% of the allowable ANSI Pitch Diameter tolerance. If greater than 40%, inspect further by measuring lead and/or viewing a cast of the thread form on an optical comparator.

When inspecting 2⅜” and 2⅞” tubing with an MRP-1000 or MRP-2000, save time by quickly checking the PD at only one location.  Because ovality isn't a concern for small diameter tubing, an average of high and low readings is not necessary

When using an MRP to inspect a coupling's Pitch Diameter, mark the location of the MRP on the face of the 1^st machined part, and record the gage reading.  Leave this 1^st machined part nearby to verify between each additional machined coupling that the gage is still set properly.

Thread Profiles not only help check for the correct thread form, proper flank engagement and possible lead error, but you can inspect for burrs by sweeping the profile around the thread cone.

The notches on lead standards are precisely machined to compensate for the error of measuring on a tapered cone, as opposed to measuring on the axis of the threads.

Avoid incorrect pitch diameter measurement by always verifying the appropriate ball contact points.  A quick check with a caliper or an OD mic will prevent this mistake.  It also helps to regularly inventory your contact points and have multiples of your most commonly used sizes.

When setting functional roll gages to zero, it’s smart practice to record the revolution count as seen on the small dial of the indicator.  Place a small piece of masking tape on the metal plate beneath the indicator, and record the rev count. This ensures you don’t machine your part one or more rev counts off nominal.

Thread inspection using thread rolls make a lot of sense when you have a better understanding of how it all works.

Both the PG-6000 and RG-7000 gages use 2 thread rolls that are precision ground to seat into the thread form and contact the thread at the pitch line.The gages are preset and zeroed to a calculated dimension for the particular thread being inspected.  The indicator on the gage reveals how the thread deviates from nominal size. This inspection is also known as a functional size inspection.  The thread rolls see variations in form, lead, taper, and height all at the same time just as a ring or plug gage does.

This is just another NOK (Nugget of Knowledge) from Jim Douglas.

To pick up machine tool errors on Rotary Shouldered Connections, it is extremely important to properly measure the thread lead.

Most of the time measuring in the middle of a connector's thread length will show an acceptable tolerance.

Our location method will pick up machine back lash (worn lead screws on manual lathes) and CNC “X” or “Z” axis servo drive errors.

Locate where the thread starts on the 45° chamfer (first scratch) and then move back one thread.  Do not exceed 360° of rotation from where the thread starts.  Then, simply place the fixed ball contact on the lead gage into the first full thread groove to take your first measurement.  After your first measurement, move the fixed ball contact up the thread axis one more thread on the same radial plane to take your second measurement. The third measurement is taken on the last inch of thread on the same axial plane.