QUICK, EASY AND AFFORDABLE MEASUREMENT OF EXTERNAL AND INTERNAL
THREAD PITCH DIAMETER – ALSO AT THE MACHINE
Thread Pitch Diameter Measurement
d2 & D2
Click on the relevant thread for more information on the thread type.
To see more on many thread types go to Thread Manual
Video: Thread Pitch Diameter Measurement External & Internal
FMS caliper and thread inserts
Inserts 22B for P 2-4mm 13-6 TPI
Inserts 21B for P 2-4mm 13-6 TPI
When asking for information or requesting a quote
the 3 most important facts are:
External and/or internal thread
THREAD INSPECTION OR MEASUREMENT?
By ”inspection” means checking threads with solid gauges and preferably with both Go and No-Go thread plug and ring gauges. This applies in most cases, to smaller diameter standard threads cut with taps or dies. Gauges for smaller standard threads are usually reasonably priced although, if gauges are for non standard threads or to be calibrated regularly, cost increases.
Measuring threads is common sense especially when setting up the machine. Making a mistake in expensive items is costly and certainly cause for concern if it is a customer that finds a fault. When measuring always measure d or D1 and preferably pitch diameter. If the pitch diameter is close to the middle of the tolerance then inspection probably doesn’t need to be as often and with mass production SPC will show how much variation there in fact is within the tolerance by the process. There will almost certainly be much less wear on solid gauges by staying away from tolerance limits.
The major diameter (d) of an external thread must not be less than the minimum of the tolerance and the minor (bore) diameter (D1) of an internal thread must not be more than the maximum of the tolerance. Both these measurements are very easy to do and a stripped (weakened) thread could be a disaster.