In-House Thread Wire Calibration

4

4 Quality

Hello,
I am wondering if I can calibrate thread measuring wires in house?
I have several sets that no one has used for a couple of years, if ever.
The condition looks brand new. I checked with our calibration house but they want 350.00. We are a small company and need to watch $$$.
It would not be as easy as calibrating a micrometer with NIST traceable carbide gage pins and then use that mic,would it? What about a pressure mic?
I would appreciate any advice.
I would like to say that I really missed this forum while it was gone.
I have learned so much and really appreciate all those who are willing to share their knowledge. Thank you,
4Quality
 
M

Michael_M

Trusted Information Resource
Re: Thread wire calibration

Several options:

1. since you do not use them, put them away and don't use them.
2. mark them as "verify prior to use". This would require you to use an instrument that is accurate enough to verify the size but you only do it prior to actually using the pins.
3. calibrate them when you need them.

I have pulled several thread gages and placed them in a bond cabinet after having no record of use for 2+ years. I added to our procedure what to do if we need the gages. We maintain the ability to use the gage but must send for calibration when finished. After 30 or so years, I have about 200 gages that are not used anymore (that are still good).
 
4

4 Quality

Hi there,
Thank you for your response.
My apologies, I left out an important part.
I want to use the Thread wires,but would like to calibrate in house if possible.
 
N

notadog

4 Quality: My answer is No! It's not as easy as you think.

Please obtain the latest version of: ASME B89.1.17-2001 and ANSI/ASME B1.16M-1984.

Temperature, Tolerance, weight, resolution, and experience are you're main problems!

Temperature: Without a stabile environment at 68°F you'll get one result and at 80 you'll get another. So you need a stabile environment.

The Tolerances on the wires are so tight that with the variation in temp you'll never know if you're result is in or out of tolerance.
Find the Nominal Diameter - the Average Diameter of the wires = ±0.000020".
Find the Max - Min wire diameters = ±0.000005" from each other.
They have to be measured using a Cylindrical Pin of 0.125, .5, and .75.
A certain amount of weight has to be applied for the applicable TPI.
Determine the Thread Wire Constant.
Measure Over the Wires - the Constant = the Pitch Diameter. That is for Metric and Inch Straight. If they are NPT Threads then the Angle must be compensated for also.

There are so many different kinds and sizes of threads that I only do the threads I've mentioned. I was told along time ago that threads are evil and after 28 years, he was right.

If you're making parts that have threads and you're not replacing the gages then take that $300/set and buy you some replacement threads. You don't need another headache than the one you've already got!

I hope this helped!
 
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