Request a Mentor on ANPT

[Cervantis]

I am a new member to this site. As a Quality Control Receiving Inspector, I have been provided a set of six step plug and ring gages for checks on NPT threads. I realize that standards do not require ANPT gages for NPT, but we have had issues with leaks and parts that do not match. Where can I find information on how to use a Six Step Gage for these checks. Training or instructions were not provided to me.

Thanks,
John

[Forestgnome]

Is there a manufacturer's name on the gages? They're usually the best source for info on how to use.

[landm1]

Hello,

I do not have their number on me here at home but it seems I used Greenfeild in the past. Talk to a sales house like Rutland or MSC and they can set you up with the factory tech. I am not sure how much luck you would have on your own.
One note, do not forget to ask about the taper gages, if you are doing incomeing inspection you are going to have a problem, you have to use them prior to cutting the thread. I think some of our gages are 6 step, ring and plug.
If you are dealing with molded plastic parts, which we do not, I think that is a real can of worms. more than likely in that application you are going to need a optical compairitor. For all of you plastic experts out there, I think the greater the mass the more the material will cantract as it cools. So near the top of your seal area, more mass, the greater the thermal distortion, trashing your taper and a gage, ring or plug , will never find it.

Check for proper truncation, crest and root. If you are dealing with male N.P.T. on metal ask your vendor if they are using "full form" inserts. If they are making female N.P.T. ask if they are using the proper N.P.T. ream.

### Do not try to use ring or plug taper gages on the finished product, you can easily damage the gage and the reading is incorrect.

Oh yea, do not forget about "dry seal" as well.

If you want to be a real cool inspector never spin the ring gage onto the part
you screw the part into the gage. I can't really explain why the is but we had a consultant school us about that.

Good luck, your machinist handbook is also a great referance, they identify all of the issues I brought up and a ton more. I would spend a half and hour reading it before you call for help, the techs always like working with those who are doing their best. These guys at Greenfeild are top notch!

Hope this helps!

LandM-1

[Forrest Addy]

Hard core gaging and adherance to standards seldom accomplishes leak proof tapered thread connections particularly in materials long on strength and corrosion resistance and short on ductility.

One essential seldom mentioned in association with pipe threads is that one member of a pipe threaded connection has to be deformable somewhat to seal correctly. You can never get so-called "dryseal" and taper pie threads to mate perfectly root with mating crest. Aint gonna happen. You have to mash the metal a little. Usually where iron pipe is used with cast iron fittings the malleable pipe will extrude in the fitting a trifle making the seal and the goo or tape sealants merely take up the tiny voids in the potential leakage paths.

That's why reconnected joints often leak and why expedients like lutes and cements are necessary where common pipe dope or teflon tape is prohibited.

Where high temperatures are a factor, plating the female thread with a softer metal compatible with the metallurgy, galvanic series, working fluid, and level of cleanliness is one possibility - gold or silver for example.

[landm1]

Wow,

I never thought about deformation, cool, makes a lot of sence. We do not do a lot of N.P.T. stuff but every time we do I always seem to learn a little more.

Thank you for the input!

LandM-1

[PixMan]

Originally Posted by landm1

Check for proper truncation, crest and root. If you are dealing with male N.P.T. on metal ask your vendor if they are using "full form" inserts. If they are making female N.P.T. ask if they are using the proper N.P.T. ream.

This part of what you've written is something that I question. It seems to me that the job of the inspector is to determine if the part meets the specifications of the print. Asking a vendor how they made something isn't part of inspection unless divulging a process was part of the original P.O. agreement.

Either the parts meet the spec or they don't. It's up to the inspector to know the difference. Ask the vendor and they'll fish for what the "right answer" would be, and that's what you'll get so the parts pass.

BTW, I found this site that seems to have a good explanation of how the different gages for ANPT threads work.

http://www.pmclonestar.com/piped/tapgage.asp


Oh, and if that Greenfield company you're referring to is the same one that was just sold to the Chinese, you may not have the same working relationship now or soon into the future.

[landm1]

Hello,

Greenfeild is now a Chinese company, bumber, yea, I gess that tec support is toast.
My stuff comes from the vendor side, we are a job shop, we tuned our game up making high pressure sensor housings for Bourns in Riverside ca. They closed that up years ago, we were one of the last shops in there. There q.c. lab and their staff was all old school, all 20 year plus guys. I guess I never even saw the application of what we made but we did make it to spec., with their support. I was so impressed that I had a couple of them come to my shop and do a little consulting when they shut it down.
There was a woman who was the director of manufactuing for the unit, same deal, 20 years +. Bourns is a large company, this unit was small but very intense. I found out she had no degree but she had been running the place for a long time. They would bring a new young collage grad, they would take one look around and figured there were easier ways to bring good news to the board room and would ask here to keep an eye on things until they could find an easier route through the company.
I guess after a few years of that they figured out what was going on and put her in charge. I wounder what happend to the guys at Greeenfield, you can probably get great thread support at Wallmart in the Greenfield area!

Oh well, just more rant,

LandM-1

[Cervantis]

Wow,

I am not worthy to have such a fantanstic responce. I appreciated the mashing of the threads/deforming comment as this was exactly what I told one of our engineers who is trying to stop leaks from his skill level. The gages came from GLASTONBURY SOUTHERN, and I have their phone number and will give them a call. Thank you for the link also. For my 1st visit, this was a valuable experience and greatly appreciated. I hope I will be able to return the favor some day.


Best,

JOHN

[Eric M]

Here's a website I stumbled upon one day, and I found it very useful: http://www.thegagestore.com/docs/How...read_Gages.htm

[Cervantis]

Thanks ERIC M. This was a good site for some good information. Now this raises a question for clarity. My background is medical devices and supplies, so I am in a new territory with these threads from my education and experience. Would this be a true statement? Can a thread be described as "going from the bottom of the root going up the flank to the crest and back down the flank on the opposite side to the bottom of the next root, and back up the flank to the top of the crest". The illustration for the L-1 on this website shows exactly this by the indication lines marked in RED.

[Eric M]

If I understand your question correctly, I think my answer would be "Yes, sort of".
To me, "one thread" could be considered from the peak of one thread, to the peak of the next thread. This "peak-to-peak" distance is also known as the "pitch".
I'm sure there are others in this forum who may be able to give you a better or more complete explanation than I have, so check back often.