Thread Gage Calibration / Verification Instruction needed

[Dale D. Barnes]

Re: Thread Gage Calibration/Verification "NEEDED"

Hey Coury,

Here is some information on threads. This is somewhat generic but will give you a starting point. There is alot more detailed information but I do not have it on electronic file. I have also attached information on ring gages.

Good Luck
Dale

 

[sarasheed]

Re: Thread Gage Calibration/Verification "NEEDED"

Please open the link" https://www.swansongage.com/images/Page-19-Swanson-Catalog.pdf"

The pitch diameter of any thread has to be measured over a set of three standard wires depending on the pitch of the thread.These standard wires are available in the market.( for the pitch 1.25 mm the cost of the three wires is $57 as indicated in the price list in the above link.)

Measuring sketch and normal constant to added to the pitch diameter to get the over wire diameter are also given in the above link.Measurements can be taken with a 0-25 mm Digital out-side micrometer of least count 1 micron.

For your example of M8X1.25,Go over wire diameter=7.188+1.0825=8.2705 and No Go over wire diameter=7.348+1.0825=8.4205mm.The accepting norms for these diameters have to be caculated and applied.These are called "Wear Limits"

Sarasheed

 

[Grizz1345]

Re: Thread Gage Calibration/Verification "NEEDED"

Below are the simple work instructions I use for calibrating thread plug gages.

1. The initial calibration is to be done by the manufacturer. The calibration certificate from the manufacturer is to become part of the permanent record.
2. Clean all surfaces to remove oil and foreign material.
3. Examine the thread plug gage for any damage or other obvious signs of wear or abuse that may affect the accuracy or function.
4. Upon re-calibration only the pitch and major diameter will be measured.
5. Set the anvil pressure on the super-micrometer to the required thread specifications.
6. Set the super-micrometer with gage block at the appropriate range (ref: .500” for ½ thread gage)
7. Select the measure-over wires that meet the Best Wire Size (BWS) required specs.
8. Measure the major diameter, 2 readings (front, back). Record readings in calibration record.
9. Measure, over wires, the pitch diameter in 3 places (front, middle, back). Subtract the constant given for the wires and record results in calibration record.

Acceptance Limits
The major diameter and pitch diameter of thread plug elements will meet the required specification tolerance for the size and pitch of the gage being checked as shown on the cert.

In the case of thread ring gages I return them to the manufacturer for calibration. I find that by returning them to the maker I get less rejections or rework.

I am sure that other people have more elaborate instructions. I have tried to keep mine simple and to the point.

Hope this all helps.
Have a great day.

 

[skappesser]

Re: Thread Gage Calibration/Verification "NEEDED"

Hello folks,
I am looking for a simple instruction on how a thread gage should be calibrated and or verified on a biannual basis. Example being a thread gage manufactured by Grenfield a M8 x 1. 25-6H – Go PD 7.188 NoGo PD 7. 348. Hope someone can help!
Thanks,
TC

Are you absitively sure you should be doing it bi-annually? How did you arrive at the 6 mo. requirement? Is the gage used a lot? Several times a day/week/month? If it were my thread gage I would calibrate it according to usage, not time. Usage wears it down, time is pretty benign to a thread gage. Keep score every time it is used, and establish a conservative threshold that triggers the calibration. Depending upon the hardness of the threads tested (I.E. steel vs. aluminum), you may have to cal it more or less often. Other variables include clean/dirty environment, finesse of the user(s), and reject rate.

 

[sarasheed]

Re: Thread Gage Calibration/Verification "NEEDED"

Please open the link : https://www.swansongage.com/images/Page-19-Swanson-Catalog.pdf

The pitch diameter of any thread has to be measured over a set of three standard wires depending on the pitch of the thread.These standard wires are available in the market.( for the pitch 1.25 mm the cost of the three wires is $57 as indicated in the price list in the above link.)

Measuring sketch and normal constant to added to the pitch diameter to get the over wire diameter are also given in the above link.Measurements can be taken with a 0-25 mm Digital out-side micrometer of least count 1 micron.

For your example of M8X1.25,Go over wire diameter=7.188+1.0825=8.2705 and No Go over wire diameter=7.348+1.0825=8.4205mm.The accepting norms for these diameters have to be caculated and applied.These are called "Wear Limits"

sarasheed

 

[jpolley21]

Re: Thread Gage Calibration/Verification "NEEDED"

Dont know of this has been added yet but here goes........
Typically verifying a threaded ring gage consists of having the Master Set Plug to go with it. In my company I send out my Plug Gages to a outside calibration company for verification. Then using the Set Plug can calibrate the ring gage itself. A good source to use for tightness of the gage and calibration techniques is on Hemcogages.com. Also there is a Military Standard that defines Ring Gage Calibration as well. I actually wrote my company procedure on Ring Calibration using these two as reference. I will try to post the Military Standard at a later date....maybe monday.
Hope this helps............

 

[calibrationd]

Re: Thread Gage Calibration/Verification "NEEDED"

It may be to late, there are many things that go in to the calibration of thread plugs, the force at which you measure, the best thread wire to use, the calculation of the constant, temperature, and the correct measuring equipment. I work for a calibration lab, and it takes all of these aspects in order to get repeating measurements. Most companies find it cheaper to send them out to be calibrated. If you want more information on either sending them out, or calibration procedures on thread plugs, I will be happy to go into either one in more detail. It will take more than just a thread though. Send me an email at dave at rmsqualityservices dot com and I will reply with more information.

 

[MichelleKay]

We are a calibration lab and use NA17-20MD-141 to calibrate thread plug gages. It is listed on GIDEP just search for the document number. We only measure pitch diameter. This is done using three 60 degree thread wires and a SuperMic.

Hope that helps!
Michelle

 

[TIMMYS - 2010]

Outsource calibration is an option. However, I caution you on the frequency of the calibration. (Bi-Annual). Thread gages can wear very quickly depending on useage, materials, environment, etc. I would suggest that you determine if you have the proper frequency before outsourcing. You may have to calibrate more frequently which would cost much more $$$.

 

[CalRich]

Hello folks,
I am looking for a simple instruction on how a thread gage should be calibrated and or verified on a biannual basis. Example being a thread gage manufactured by Grenfield a M8 x 1. 25-6H – Go PD 7.188 NoGo PD 7. 348. Hope someone can help!
Thanks,
TC

A lot of people have responded, but some tangents have been taken (e.g. talking about calibration of adjustable thread rings, which is totally different.)
calibrationd is correct in that there are many factors that come into measuring threads, and simply having a procedure isn't going to allow you to calibrate them immediately. Generally, threaded plugs are measured using the three-wire method. A measurement is taken with three thread wires seated into the threads. The thread wires are tangent to the pitch diameter inside the thread. A simple calculation can be made to determine the pitch diameter once the measurement over wires is made. Van Keuren illustrates it very well here. Of course, measuring threaded plugs can get very complicated when getting into threads of various angles and types (ACME, Buttress, Helical...)
The trick is having all of the correct equipment and lab environment to get the right readings. That's why you should take the advice of many here and get it calibrated by an accredited outside source.