How do I calibrate NPT Thread Plug Gages?

[Tim Roberts]

Hello, my Thread plug gage cal tech can do the parallel thread plug gages, but is having difficulty with the NPT thread plug gages.

How would he go about calibrating a Van keuren 1/8-27 NPT-L1 using the following:
Mahr Federal 828CIm Universal measuring machine
Mitutoyo 516-422-22 Square gage block set
Van Keuren 1601-5-80TPI Thread Wire
Nikon V-12 Profile Projector

This was what the previous technician used to calibrate these thread plugs.
Measurements were
E1 Pitch Diamter
L1 Length

Any help would be useful.

 

[Hershal]

Tim, I am sure there are folks here with experience in those plugs. You should get an answer shortly.

 

[harry]

You may want to go through the related threads.

 

[Mr.Happy]

NPT thread plug gages are very hard to calibrate!
I would advise you to send them out to a certified calibration lab, even than I noticed some small differences from the original certificate.
If you don’t know witch lab to choose than ask the lab upfront to provide you with a MSA study over NPT thread plug gages. Or send out a new NPT thread plug gage, that you purchased with an original certificate, to different labs.

 

[Tim Roberts]

The issue is that we are an ISO 9001/17025 certified lab. We have the equipment but the knowledge base left with a tech who moved on.

If someone knows the steps to take, what needs to be measured, that would be extremely helpful.

 

[Hershal]

Tim, you will NOT like my answer, but I want to spare you serious issues later.

You MUST - under ILAC and AB rules, inform the AB when personnel changes affect the quality of measurements. In other words, a tech who does clean-up is differently that one who does onlink.

There must be a distoonder

 

[Jim Wynne]

What is a distoonder?

 

[Hershal]

What is a distoonder?

Huh? What?

 

[Jim Wynne]

Tim, you will NOT like my answer, but I want to spare you serious issues later.

You MUST - under ILAC and AB rules, inform the AB when personnel changes affect the quality of measurements. In other words, a tech who does clean-up is differently that one who does onlink.

There must be a distoonder

What is a distoonder?

Huh? What?

See the bit in bold above.

 

[DietCokeofEvil]

Hello, my Thread plug gage cal tech can do the parallel thread plug gages, but is having difficulty with the NPT thread plug gages.

How would he go about calibrating a Van keuren 1/8-27 NPT-L1 using the following:
Mahr Federal 828CIm Universal measuring machine
Mitutoyo 516-422-22 Square gage block set
Van Keuren 1601-5-80TPI Thread Wire
Nikon V-12 Profile Projector

This was what the previous technician used to calibrate these thread plugs.
Measurements were
E1 Pitch Diamter
L1 Length

Any help would be useful.

To be honest, the only way you could measure notch P.D. with that equipment is to perform a two wire method calibration, which I am not a fan of. If you want the P.D., you need to use a taper sine block or a sine bar, and you also need to know that the taper angle of your gage is in tolerance. I know that the tapered sine block gives you the small end P.D., so you would need to take extra measurements and do some math to get your notch P.D. Small end P.D. is completely useless IMO.