Standard for pitch diameter measurement

[qaqc1]

I have following questions on measurement of pitch diameter for ASME B1.1 UNC threads.

1)Is there a standard which gives guidelines on how to
determine pitch diameter of threads by 3- wire method.

2)What is the fastest method on measuring pitch diameter
for fasteners. (I am referring to B1.1 UNC)

 

[funnelguy]

1) Machinery's Handbook gives complete information on this subject.

2) It depends. Try talking to a few industrial supply houses.

 

[BillPSU]

Threads are similar to gears as they are made up of mutiple features which interact with each other. The thread form can be inaccurate and the pitch diameter inaccurate yet measurement over wires shows the PD being correct. The best approach to measure a thread is a functional test which is a go/no-go test. Thread ring gage or thread plug gage are the standards. Assuming you have good thread form the quickest way to measure an external thread is a thread snap gage, again this is a go/no-go situation where you do not know the actual diameter. Internal threads are almost always measured with a plug gage.

 

[unclesyd]

Once you have an understanding of this method here is a website that will be of some help. If you don't need any accuracy there are triangular gauge bars that I found easier to work with.

http://www.machinist-calculator.com/Thread-Measure-Eng.html

As posted above by BillPSU nothing beats the proper gages. If you purchase thread gauges please treat that as per the manufactures instructions.
If you are considering this for a production application there are numerous thread measuring stands that do a good job.