This may only be because I have to translate it to my first language.......But checking the MINOR DIAMETER of the ring, means the 'smallest' diameter.....The one 'at the top of the tooth' of the thread??? With which instrument should we check it?
This does get confusing because the terms do not refer to the same diameters on the male and female threads.
Let’s start with the terms:
Major Diameter: The largest diameter of any thread.
Minor Diameter: The smallest diameter of any thread.
Root: When looking at a thread, regardless of male or female, gage or product, the root is the bottom of the physical thread form. So…
- Root of external product thread = Minor Diameter
- Root of thread plug gage = Minor Diameter
- Root of internal thread = Major Diameter
- Root of ring gage = Major Diameter
Crest: When looking at a thread, regardless of male or female, gage or product, the crest is the top of the physical thread form. So…
- Crest of external product thread = Major Diameter
- Crest of thread plug gage = Major Diameter
- Crest of internal thread = Minor Diameter
- Crest of ring gage = Minor Diameter
When you said to 'Use plain pin gages to check the minor diameter', were talking about the plug or the ring.
When I said to ‘use plain pin gages to check the minor diameter’ I was talking about the ring gage. The ring gage minor diameter is one of the fastest wearing diameters of a ring gage.
If you were talking about the ring, excuse me, but I have no clue how we will do that???
First you set the ring gage to the set plug gage.
Once that is accomplished, use GO/NOGO Plain Plug Gages to check the ring gage minor diameter.
Depending on how accurate you wish to be, you may wish to purchase class X plain plug gages made specifically to check the ring gage minor diameter. You will need one set of gages for the GO ring gage and a different set of gages for the NOGO ring gage. The tolerance on the minor diameter is usually large enough to allow the minor diameter to be checked with class ZZ plain pins out of your pin gage set.
Do not check this diameter on the ring gage with a caliper because you will not get an accurate measurement.
The internal product thread minor diameter should also be checked. After being checked with a working thread plug gage, the minor diameter should be checked. In this case GO/NOGO plug gages could be used or any other measurement tool which is sufficient for the job.
I hope that helps.
