I'm just throwing this out for discussion... I have my answers from a great source and am proceeding as I feel comfortable to... but I thought the forum may be interested in hearing this...

I'm setting up some a hands-on gage training for new employees at my company (part of new employee orientation). This training will begin with a PowerPoint presentation including the do's and don'ts as well as a visual introduction to the gages... then proceeding to hands on practice.

While I was preparing my material on attribute gages, I remembered we have (what I thought was) a strange rule in our work instruction for thread gages.
The No-Go end is allowed to enter the part up to 1.5 turns.

In questioning the appropriate people at my company about this, I was informed that industry standards actually allow up to 3 full turns of the No-Go end and the dimension is still considered good.

Since the person I spoke with could not remember where they obtained this information, I decided to do some digging to verify the validity of the statement.

I have spoken with two people at Glastonbury Southern Gage (including one of their top engineers) who informed me that it's actually a 3 turn rule for unified (English) threads and for metric, it's 2 turns.
Thus, on an English thread plug, the no-go end MAY enter the part up to 3 turns and on a metric thread plug, the no-go end MAY enter the part up to 2 turns.
He did advise, however, to stay away from using this rule as common practice as to eliminate "gray" areas, but said that it is indeed an industry standard.

Everything I have read on forum posts states that the No-Go end cannot go at all... Feel free to comment.

I have spoken with two people at Glastonbury Southern Gage (including one of their top engineers) who informed me that it's actually a 3 turn rule for unified (English) threads and for metric, it's 2 turns.
Thus, on an English thread plug, the no-go end MAY enter the part up to 3 turns and on a metric thread plug, the no-go end MAY enter the part up to 2 turns.
He did advise, however, to stay away from using this rule as common practice as to eliminate "gray" areas, but said that it is indeed an industry standard.

Everything I have read on forum posts states that the No-Go end cannot go at all... Feel free to comment.

Hi jane_ackerman,

The information you have received is correct, except for one thing - sheet metal has a different requirement - it is 1.54 turns of the no-go gage.

Thanks for that update Carol.
It's another great day for learning : )

This is a really fuzzy area, and I've always contended that "industry standards" that aren't officially codified and controlled, (A) can't be referenced on a drawing and (B) are generally useless. What's important is that customer and supplier both understand the requirements, wherever they come from. It's helpful to know that some suppliers might be working under the assumption that the "industry standard" will prevail, so as to guard against misunderstandings, but what really matters is making sure the specifications correctly communicate design requirements. There could be instances where x turns of engagement of the no-go member will be unacceptable, and others, such as relatively deep threads, where several turns might be OK.

In our org as well we had the practice of accepting 1.5turns across as this was acceptable by all thread standards(English & Metric) I too had never come across the sheet metal. Thats the learning for the day. If I am not wrong (as per the info I have got) they are specified in the IS standard...

I assume these a straight threads since NPT gauges are step gauges?

I have attached a photo of the type of thread gage that I was speaking of.
I am not familiar with what an NPT step gage is.
Sorry.

I have attached a photo of the type of thread gage that I was speaking of.
I am not familiar with what an NPT step gage is.
Sorry.

"NPT" stands for National Pipe Thread (http://en.wikipedia.org/wiki/National_pipe_thread). The threads are conically tapered to provide better sealing joints.

our practice for straight threads is 3 turns.
All our parts are SI units.

Who changed my thread subject name?
I didn't include the last part that states "No-Go end is allowed to enter the part up to 1.5 turns"
I'd appreciate that being removed, as it is not a true statement and I didn't include it in my original post.
Thank you in advance.

Who changed my thread subject name?
I didn't include the last part that states "No-Go end is allowed to enter the part up to 1.5 turns"
I'd appreciate that being removed, as it is not a true statement and I didn't include it in my original post.
Thank you in advance.

mods tend to do that to give as much info as possible in the title.
Don't take it personally, but don't be afraid to question authority either :)

Who changed my thread subject name?
I didn't include the last part that states "No-Go end is allowed to enter the part up to 1.5 turns"
I'd appreciate that being removed, as it is not a true statement and I didn't include it in my original post.
Thank you in advance.

Jane,

We frequently rename thread titles to aid in the search function. If a user comes in looking for no-go gaging on threads and 1.5 turns , they will be directed to this excellent thread.

My appologies if you were offended.

I do thank you for an excellent thread. A lot of great information in your original post.

Jane,

We frequently rename thread titles to aid in the search function. If a user comes in looking for no-go gaging on threads and 1.5 turns , they will be directed to this excellent thread.


But if such a search would still find this thread, even if the title hadn't been changed, no?

Perhaps it could be changed to reflect that the "no-go end may enter based on the thread type"?
Just a thought... to make it more of a true statement.
Thanks.

Perhaps it could be changed to reflect that the "no-go end may enter based thread type"?
Just a thought... to make it more of a true statement.
Thanks.

I think perhaps a question mark at the end might clear it up.

Get me a consensus of what you want the thread title to be and I will change it to reflect the consensus opinion.

How about "ANSI Unified thread plug gage - How many turns allowed for no-go end?" (Confirm we refer to ANSI Unified thread?) There is a Standard ANSI B 1.2.

My 23rd edition of Machinery's Handbook says (p1642) "NOT GO (H1) Thread Plug Gages. NOT GO (H1) thread plug gages when applied to the product thread may engage only the end threads (which may not be representative of the complete thread.) [deleted for space] . . . acceptable when the NOT GO (H1) thread plug gage applied to the product internal thread does not enter more than three complete turns. The gage should not be forced. Special requirements such as exceptionally thin or ductile material, small number of threads, etc., may necessitate modification of this practice."

We make precision parts in our plant. Some of our parts have threads only 1-3 turns long. The 'Nogo' must not go in at all. I would think that it is all a matter of common sense, w/ the max of 3 turns on larger parts.

... I've always contended that "industry standards" that aren't officially codified and controlled, (A) can't be referenced on a drawing and (B) are generally useless. ...Jim, I assume that when you speak of “industry standards” not being officially codified and controlled, you are speaking of the unofficial rule-of-thumb, not the ANSI/ASME/ISO/SAE standards. These are codified, can be controlled and are referenced on drawings.

Jim, I assume that when you speak of “industry standards” not being officially codified and controlled, you are speaking of the unofficial rule-of-thumb, not the ANSI/ASME/ISO/SAE standards. These are codified, can be controlled and are referenced on drawings.

I understand, hence the scare quotes (http://www.cogs.susx.ac.uk/doc/punctuation/node31.html) around "industry standards."

Get me a consensus of what you want the thread title to be... How about "ANSI Unified thread plug gage - How many turns allowed for no-go end?" (Confirm we refer to ANSI Unified thread?) There is a Standard ANSI B 1.2. My 23rd edition of Machinery's Handbook says...The current edition of the Machinery’s Handbook is the 27th. How old is that 23rd edition?

As for the standard being discussed, yes, one gaging requirement for the Unified Thread is specified in ANSI B1.2, but the gaging requirement is also specified in BS 919; JIS B 0255; JIS B 0256; SAA AS 3635; and an ISO standard that I can not identify at the moment. Then there is a similar list of requirements for NPT, NPTF, ANPT, BSPP, BSPT, ACME, Buttress, Metric, Whitworth, Trapezoidal and other threads.

Use requirements for thread gages vary based on the standard that defines them. When a part is designed, the standard requirements for the threads should be stated on the print. Gray areas in the standard, if critical, need to be further defined on the print. I believe that, if you check the wording in the ANSI B1.2, for example, you will find wording defining the use of the NOGO gage which states something to the effect of: Shall not enter the part not more than 1-1/2 to 3 turns, unless otherwise specified by the customer. This wording covers short parts or long parts or specific product requirements not obvious to the maker of the component part, as long as engineers fully define the component requirements, and quality professionals review the standards for their specific idiosyncrasies.

The current edition of the Machinery’s Handbook is the 27th. How old is that 23rd edition?

As for the standard being discussed, yes, one gaging requirement for the Unified Thread is specified in ANSI B1.2, but the gaging requirement is also specified in BS 919; JIS B 0255; JIS B 0256; SAA AS 3635; and an ISO standard that I can not identify at the moment. Then there is a similar list of requirements for NPT, NPTF, ANPT, BSPP, BSPT, ACME, Buttress, Metric, Whitworth, Trapezoidal and other threads.

Use requirements for thread gages vary based on the standard that defines them. When a part is designed, the standard requirements for the threads should be stated on the print. Gray areas in the standard, if critical, need to be further defined on the print. I believe that, if you check the wording in the ANSI B1.2, for example, you will find wording defining the use of the NOGO gage which states something to the effect of: Shall not enter the part not more than 1-1/2 to 3 turns, unless otherwise specified by the customer. This wording covers short parts or long parts or specific product requirements not obvious to the maker of the component part, as long as engineers fully define the component requirements, and quality professionals review the standards for  their specific idiosyncrasy.
Absolutely, Wayne! I'm old, semi-retired and rarely have need for a more recent version when many things are available via internet. I think I may have some editions in boxes in the garage which go back to the 60's and 70's! Hence my mention of WHICH edition!

The operative phrasing throughout the years has always been some version of "use common sense! If you have only 2 threads in a thin sheet metal panel, reference to three threads is invalid."

Jim & Wes,
What are you guys doing up so late. I thought it would be hours before you caught my remarks.:D You guys are fast!:applause: I don't intend to offend, I just have never learned how to be socially appropriate.:o

WOW! This has turned into an awesome discussion!!!
Thanks so much to all of you who have done some research and provided the quotes and sources.

Wes,
Since there are various standards based on thread type, how about simply:
"Thread Gages - How many turns allowed for no-go end?"

Again, a huge thanks to all who have provide input.
Jane

I looked this up in my copy of the ANSI/ASME B1.2-1983 std. It appears that Wes's quote from the Machinery Handbook of several days ago is a direct quote of section 4.2.1 (page 13) of B1.2-1983. The wording is identical.

WOW! This has turned into an awesome discussion!!!
Thanks so much to all of you who have done some research and provided the quotes and sources.

Wes,
Since there are various standards based on thread type, how about simply:
"Thread Gages - How many turns allowed for no-go end?"

Again, a huge thanks to all who have provide input.
Jane
How about
"Thread gages - using the no-go end correctly"?

That works for me.
Thanks

Just to add to the confusion.....

I recall being taught that all the stress in a thread is handled by the first 3 pitches, hence allowing this to go oversize one would imagine would weaken the strength of the fastener ??

Maybe ??

New to this forum...My company just got me a Pratt & Whitney Super Mic to bring our calibration back in house. I have procedures for just about every thing I need except NPTF plugs. I know I have to measure pitch diameter at the gaging notch, and major at the small end. I have a 3/4 TPF master and flat tapered probes. Is there anything fundamentally wrong with what I have so far? What is the Measure Over Wire formula? What else is needed to be able to certify this gage? I already have the pipe thread standards. I would greatly appreciate the help with this.

New to this forum...My company just got me a Pratt & Whitney Super Mic to bring our calibration back in house. I have procedures for just about every thing I need except NPTF plugs. I know I have to measure pitch diameter at the gaging notch, and major at the small end. I have a 3/4 TPF master and flat tapered probes. Is there anything fundamentally wrong with what I have so far? What is the Measure Over Wire formula? What else is needed to be able to certify this gage? I already have the pipe thread standards. I would greatly appreciate the help with this.

Hello Jeremy! Welcome to The Cove Forums. :bigwave: :bigwave:

It is weekend and I am sure that the Metrology/Calibration experts here at The Cove will respond next week.

Look at this thread: "How to properly check (British Standard) threads?" (http://elsmar.com/Forums/showthread.php?t=26456)

This thread has some good posts and other links to topics that may be of interest to you.

I hope this helps you to get started.

Stijloor.

How about
"Thread gages - using the no-go end correctly"?Wes, I see that the name of this thread has not been changed. :agree1:Your suggestion: "Thread gages -using the NOGO end correctly." is good for the preceding discussion; however; the discussion of pipe gage calibration really needs its own thread.

What is the Measure Over Wire formula?Being that the NPTF thread is a 60 degree thread, the formula remains the same as that for a UN-Series, 60-degree, straight thread. Same best-wire size and same constant.

New to this forum...My company just got me a Pratt & Whitney Super Mic to bring our calibration back in house. I have procedures for just about every thing I need except NPTF plugs. I know I have to measure pitch diameter at the gaging notch, and major at the small end. I have a 3/4 TPF master and flat tapered probes. Is there anything fundamentally wrong with what I have so far? ... What else is needed to be able to certify this gage? ... I would greatly appreciate the help with this.My suggestion for self-calibrating taper pipe gages is to purchase masters. Have the masters calibrated at a gage maker, not a calibration laboratory.

NPT, NPTF, ANPT, and BSPT are all difficult to calibrate by direct measurement. I know of several calibration laboratories, which are well know for their skill at measuring thread gages, who do not calibrate taper pipe gages properly. Please do not make me go into the details of my investigation on this topic. We sell calibration services and it is now our practice to send all taper pipe to a gage maker.

Something interesting about taper pipe gages: NPT Taper Pipe gages have a broad tolerance. A part could be checked with two gages. One gage made to one end of the allowable gage tolerance may find the part good. The other gage made to the opposite end of the gage tolerance could find the part bad. Both gages are within calibration and are considered good. They even may have been made on the same day by the same gage maker. Consistency from gage to gage is very difficult to achieve.

Some of my customers have come to me with this type of gage irregularity. The solution to this problem, and to homogenize multiple taper pipe gages, is to purchase a master. When the master is used, the working gages are marked with a gage point which is then consistent for all gages set with that master. If your customer is checking the product upon receipt, calibrating their gage to your master will also help avoid disputes.

Something interesting about gage disputes: By industrial standard, if a part is measured by two gages which are both in calibration, and either gage passes the part, the part is to be considered good, even if the other gage fails the part. First comment is that most disputants that I have talked to believe that if either gage fails the part, the part is bad. Second, when it comes to taper pipe gages, I would only consider them calibrated is they were checked with a master.

Wes, I see that the name of this thread has not been changed. :agree1:Your suggestion: "Thread gages -using the NOGO end correctly." is good for the preceding discussion; however; the discussion of pipe gage calibration really needs its own thread.I have changed the thread title, primarily as an aid for folks using search engines to find reference material on the topic.

gage calibration
I agree with you the gage calibration discussion merits its own thread, but I am reluctant to split off posts from this thread to do so. I have a counter proposal:
Please start a completely new thread with a post about your views on calibrating/certifying pipe thread gages (plug, ring, straight, tapered, using masters, air gages, measuring over wires, etc.)

As a former manufacturer who continually struggled with gaging disputes about tapered threads, I am pretty sure many folks would be interested in such a thread. There were certainly a lot of gaging "myths" floating around, even among so-called experts.

As part of that thread, it might be very useful to post a list of the thread Standards and where they might be obtained.

Another part of that discussion thread (or a companion thread) might address the comparative value of using air gages, snap gages, step gages, wires, thread mikes, rings, plugs, optical, etc. methods of gaging and measuring.