Thread Ring Gauge UNJ vs UN

J

Jeenan

#1
Hi every one, I'm back again with a thread issue....

We need to check a .375-24 UNJF MALE thread, so we bought a .375-24 UNJF thread ring gauge.

Here where the problems begin.....

I red somewhere that there is a little difference between a UN & UNJ thread ring (for the GO, the NOGO is the same....)

I also red that on a thread plug, there is no difference between a UN & UNJ......

So when it's time to check the UNJ thread ring, how do we proceed....
How can we check a UNJ ring, if there is no UNJ thread plug master.....

Tell me if I got everything wrong :confused: or if I'm right, what is the solution........:(

Thanks!!!
 
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E

easy-goin

#2
First get a copy fo AS 8879 Aerospace Standard, this covers the specifications for screw threads - UNJ Profile. On an external "J" thread there is a root radius, to check a UNJ thread ring you definately need a UNJ plug master.
 
U

Umang Vidyarthi

#3
Hi every one, I'm back again with a thread issue....

We need to check a .375-24 UNJF MALE thread, so we bought a .375-24 UNJF thread ring gauge.

Here where the problems begin.....

I red somewhere that there is a little difference between a UN & UNJ thread ring (for the GO, the NOGO is the same....)

I also red that on a thread plug, there is no difference between a UN & UNJ......

So when it's time to check the UNJ thread ring, how do we proceed....
How can we check a UNJ ring, if there is no UNJ thread plug master.....

Tell me if I got everything wrong :confused: or if I'm right, what is the solution........:(

Thanks!!!
:bigwave:Welcome back jeenan:bigwave:

The only difference between UNJ 'GO' & UN 'GO' is that UNJ 'GO' ring gauge has enlarged minor dia to clear the large root radius. If UN 'GO' is used to measure UNJ, the gauge will reject the component. But UN 'NOGO' is identical to UNJ 'NOGO'

2.The UN & UNJ thread plug gages are interchangeabe.

3. Your gauge must have come with a calibration certificate, else you may look for an accreditated lab in your area. You also need to determine the calibration cycle for the gauge.

Hope this helps

Umang :D
 
J

Jeenan

#4
Thanks Umang,

we try to keep the calibration INSIDE.....

With the UN thread ring, we have UN master plug.....But what about a UNJ......since it's "split' thread ring, I know we can not check it with 'touch' probe.....

I red that the best way to check a split ring is with master plug & little bit of oil......But what if the plug DOES NOT EXIST.......:confused:

Thanks!!
 
U

Umang Vidyarthi

#5
Thanks Umang,

we try to keep the calibration INSIDE.....

With the UN thread ring, we have UN master plug.....But what about a UNJ......since it's "split' thread ring, I know we can not check it with 'touch' probe.....

I red that the best way to check a split ring is with master plug & little bit of oil......But what if the plug DOES NOT EXIST.......:confused:

Thanks!!
When checking the UNJ threads, standard UN style Work Plug Gages are used ( you already have a UN master plug). If UNJ gages are ordered from a gage maker, the gage maker will supply the standard UN gage members with a handle marked UNJ.

Hope this solves your problem.

Umang :D

THREAD NOMENCLATURE
UN = Basic Unified National thread series
UNJ = Basic Unified National thread series with external thread controlled root radius
UNS = Special Unified National thread series
UNJS = Special Unified National thread series with external thread controlled root radius
UNC = Unified National Coarse thread series
UNJC = Unified National Coarse thread series with external thread controlled root radius
UNF = Unified National Fine thread series
UNJF = Unified National Fine thread series with external thread controlled root radius
UNEF = Unified National Extra Fine thread series
UNJEF = Unified National Extra Fine thread series with external thread controlled root radius
 
J

Jeenan

#6
So that means, If I got it right:lmao:........I check the UNJ THREAD RING GAUGE, with a UN MASTER PLUG.....(exactly like if I was checking a UN THREAD RING).....That means that I can not make the difference between a UN or UNJ when I check it with Master Plug......I have to thrust the seller that say it is a UNJ........:biglaugh::biglaugh:

Thanks!!!!:thanx:
 

Wayne

Gage Crib Worldwide
#8
How can we check a UNJ ring, if there is no UNJ thread plug master.
;)Here is the procedure in outline form:
1.
Use the Set Plug Gage: To calibrate your 3/8”-24 UNJF-3A GO/NOGO Ring Gages you will use 3/8”-24 UNF-3A GO/NOGO Truncated Set Plug Gages. As is common with setting threaded ring gages, the set plug gage sets and checks all features except the minor diameter of the screw thread ring gage.
2.
Use plain pin gages to check the minor diameter: This should be standard procedure for calibration of all screw thread ring gages. The minor diameter is one of the fastest wearing diameters on a screw thread ring gage.

To obtain the gage specifications you can gather that data off the original gage maker’s Long Form Certification or the data can be generated by using one of the commercially available thread engineering software programs, like ThreadTech.
…to check a UNJ thread ring you definitely need a UNJ plug master.
:(Sorry to disagree here. The UNJ ring does not have a radius and does not check the root radius on the product screw thread. The UNJ plug master, which is better referred to as a Truncated Set Plug gage also does not have a root radius. The Truncated Set Plug Gage is identical regardless of how it is marked: UN or UNJ.

1. The only difference between UNJ 'GO' & UN 'GO' is that UNJ 'GO' ring gauge has enlarged minor dia to clear the large root radius. If UN 'GO' is used to measure UNJ, the gauge will reject the component. But UN 'NOGO' is identical to UNJ 'NOGO'. 2. The UN & UNJ thread plug gages are interchangeable.
:agree1:This is a fully accurate statement. I would only add for clarification: The UN & UNJ Work Plug gages are interchangeable. Also the UN & UNJ Set Plug gages are interchangeable. Work Plugs are for checking product and Set Plugs are for checking ring gages.

With the UN thread ring, we have UN master plug...But what about a UNJ....since it's "split' thread ring, I know we cannot check it with 'touch' probe.
:applause:Jeenan, you are so right not to try to calibrate an adjustable ring gage with a touch probe. Please read: Calibration by Direct Measurement for more information.

When checking the UNJ threads, standard UN style Work Plug Gages are used (you already have a UN master plug.
:confused:This topic gets confusing when talking about checking product threads and also checking gage threads. Let me read back to you what I think you said here: When checking the UNJ internal threads, the standard UN Work Plug gages are used. So if you have standard UN work plug gages you can check your UNJ product by using them. If that is what you meant then this is a fully correct statement.

So that means, If I got it right: I check the UNJ THREAD RING GAUGE, with a UN MASTER PLUG.....(exactly like if I was checking a UN THREAD RING).....That means that I cannot make the difference between a UN or UNJ when I check it with Master Plug
:cool:That is true until you look at the minor diameter. The gage maker should have added a value and tolerance for the minor diameter on the Long Form Certification.

Please refer to UN vs. UNJ for more details.

Jeenan; I hope this has been helpful.
 
J

Jeenan

#9
Many thanks again Wayne.....

But just a couple of clarification:

- When you said to 'Use plain pin gages to check the minor diameter', were talking about the plug or the ring.......If you were talking about the ring, excuse me, but I have no clue how we will do that???
- 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 wich instrument should we check it??? (I hope that is clear, if not, let me know, I'll include a drawing....)

Thanks!!!
 

Wayne

Gage Crib Worldwide
#10
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.:bonk:

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.:cool:
 
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