Measuring Solid Thread Ring Gages

Calibration Kid

Starting to get Involved
#1
I need a thread expert!

Please correct me if anything I say is incorrect. I am a younger guy trying to learn.

I have a customer who needs their solid thread ring gages calibrated. More specifically, ACME rings. I know the easiest way and industry standard is to purchase wear check plugs. This is too costly for us because these ring gages are sizes that don't come around often.

My boss is convinced that I should be able to measure them. Manufacturers measure them so why cant we? We have excellent equipment. A Pratt & Whitney Labmaster with an internal probe for switching out the correct sized ball probes. There is a procedure in the manual for calibrating internal threads, so the machine was designed to measure them.

Why are there no other calibration labs that will calibrate solid thread rings? Even the manufacturers like PMC Lone Star wont calibrate them.

The measurement I struggle with is Pitch Diameter. I have had an expert tell me that measuring pitch diameter on a ring cannot be done with any kind of accuracy.

The formula I am using is CONSTANT = [1.93335 X (1/PITCH)] - [2.9939 X BALL/WIRE SIZE]

My pitch diameter is -0.005" or more from the manufacturers pitch diameter. Gage has not been used.

Any help will be greatly appreciated! Or if anyone knows of thread measuring training? That would be great too.
 
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Jen Kirley

Quality and Auditing Expert
Staff member
Admin
#2
The question is, can you measure with discrimination that adequately exceeds that of the thread gage? To what class is the gage expected to operate?

Most people find the cost exceeds the value, and just replace the thread gage.

P.S. there may be some more insights in the related threads linked at the bottom of this page.
 

Calibration Kid

Starting to get Involved
#3
Thanks for the response.

Class 2G

These are some medium sized ACME rings so if I can just figure out what is wrong with my setup, it will definitely be worth while as these ring gages are too costly to replace often.

I follow the instructions given by Pratt & Whitney and don't get what the manufacturer gets.

P.S. no luck with the links at the bottom of the page. I have been trying to find info about solid ring gage calibration online for a long time now. :deadhorse:


I guess I need to talk to someone who manufactures thread gages?
 

Calibration Kid

Starting to get Involved
#4
I need a thread expert!

Please correct me if anything I say is incorrect. I am a younger guy trying to learn.

I have a customer who needs their solid thread ring gages calibrated. More specifically, ACME rings. I know the easiest way and industry standard is to purchase wear check plugs. This is too costly for us because these ring gages are sizes that don't come around often.

My boss is convinced that I should be able to measure them. Manufacturers measure them so why cant we? We have excellent equipment. A Pratt & Whitney Labmaster with an internal probe for switching out the correct sized ball probes. There is a procedure in the manual for calibrating internal threads, so the machine was designed to measure them.

Why are there no other calibration labs that will calibrate solid thread rings? Even the manufacturers like PMC Lone Star wont calibrate them.

The measurement I struggle with is Pitch Diameter. I have had an expert tell me that measuring pitch diameter on a ring cannot be done with any kind of accuracy.

The formula I am using is CONSTANT = [1.93335 X (1/PITCH)] - [2.9939 X BALL/WIRE SIZE]

My pitch diameter is -0.005" or more from the manufacturers pitch diameter. Gage has not been used.

Any help will be greatly appreciated! Or if anyone knows of thread measuring training? That would be great too.
 

Michael_M

Trusted Information Resource
#5
I don't know if this helps or not, but I believe most thread rings are calibrated using a set master 'plug'. This is for the rings that are adjustable so I don't know if there is a difference between 'solid' and this type. I have more trust to devices that can give me actual measurements instead of "accept/not accept" criteria.

Do you have to calibrate your tools to a specific standard? If you do it in-house you may not be able to calibrate to this standard.

Can the device you want to use be tested to verify. Can you measure an OD thread that you check with a pitch micrometer and compare the two readings?
 

dwperron

Trusted Information Resource
#6
Hey Calibration Kid,

It's good to see a technician who is trying to do the job right. You sound like you have the right equipment for the job. What I have discovered is that these measurements require a lot of practice to get the technique down so that you minimize errors, but you can get good and repeatable readings.

I'm going to drop a name on you:

Andrew Sylvain
860-286-8181 x230
[email protected]

He has been very helpful to us in getting information on making thread measurements on the LabMaster. Contact him, state your problem, and I believe he will be able to get the right person working with you to help.
 

Calibration Kid

Starting to get Involved
#7
Thanks for the reply. And yes, my understanding is that most thread ring gages here in the U.S. are adjustable. There is a difference, solid rings cannot be set to a set plug because they cannot be adjusted. I am looking for assistance in measuring these solid rings because some people say its not possible.

When you ask about calibrating my tools are you talking about my Labmaster? We have Pratt & Whitney come out. Our equipment is calibrated to 17025 requirements. We are a calibration lab.

The device has been verified. I only have problems when trying to calibrate internal threads. Thank you for the suggestions though!
 

Calibration Kid

Starting to get Involved
#9
Hey dwperron,

Thanks for the reply and yes, I just want to understand and know I am doing it right.

The thing that sucks is I can repeat but my measurements differ from the manufacturers measurements way too much.

And hey, thank you very much for the name drop. I really appreciate it. I have actually been in contact with them him already though. He refered me to Pete VanWhy who is their thread expert. He gave me some tips but nothing has changed. He says he doesnt know anything about ACME threads though:(
 

Calibration Kid

Starting to get Involved
#10
dwperron,

It isn't a typo, that is the formula I am using. It is definitely possible that there is a mistake. I got this formula from a thread gage manufacturer and maybe they gave it to me with a typo.

I look at the link you sent me and I don't see any formulas for calculating constant. Is it right in front of me and I am missing it haha?
 
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