Thread Go-No Go Gages

[freudianfloyd]

Could somebody tell me how they calibrate thread gages, or how they go out of tolerance for that matter? I recently pulled these out of the scrap bin at work, and after looking them over the threads all look perfect. I know these things are not cheap, and they look cool, so I saved them.

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I'm just curious why a quality department would ever get rid of these. Thoughts?

 

[WWheeler]

Here's an example of one machine set up specifically to calibrate thread gauge (pardon the cheesy music):

I believe our Quality lab would do similar but a lot slower with a CMM taking one measurement at a time.

Could it be that the gauges are no longer needed, perhaps for a discontinued part or assembly?

 

[helterskelter]

Never seen anyone attempt to calibrate them in-house. Maybe at huge companies. Typically they're sent out to a calibration lab. They were most likely discarded as part of a defunct product line. They're so specialized there's no point keeping them if you no longer make the parts. And if you set up a new product line you'd buy new gages.

 

[freudianfloyd]

Here's an example of one machine set up specifically to calibrate thread gauge (pardon the cheesy music):

I believe our Quality lab would do similar but a lot slower with a CMM taking one measurement at a time.

Could it be that the gauges are no longer needed, perhaps for a discontinued part or assembly?

It's possible they are no longer used, but some of them are pretty common sizes, like 5/16-18.

 

[freudianfloyd]

Never seen anyone attempt to calibrate them in-house. Maybe at huge companies. Typically they're sent out to a calibration lab. They were most likely discarded as part of a defunct product line. They're so specialized there's no point keeping them if you no longer make the parts. And if you set up a new product line you'd buy new gages.

They probably aren't worth much to anybody, I just thought they were cool.

 

[helterskelter]

You might get a little bit on ebay. But they're used gages. When I set up a new process something like thread gages I'd always buy new. Not worth dinking around with used gages and getting them calibrated. New ones come with a NIST cert.

edit: I looked real quick and a 5/16-18 is ~80$ from Mcmaster. So might be worth selling.

 

[freudianfloyd]

You might get a little bit on ebay. But they're used gages. When I set up a new process something like thread gages I'd always buy new. Not worth dinking around with used gages and getting them calibrated. New ones come with a NIST cert.

edit: I looked real quick and a 5/16-18 is ~80$ from Mcmaster. So might be worth selling.

That 6"-8 NPT gage sells for over $900 new too.

 

[LennyTheLizard]

They can get damaged if an operator drops them. I guess you could probably visually see a dent or dinged thread on there though. At our plant, we do have to replace them occasionally due to "out of calibration".

 

[helterskelter]

That 6"-8 NPT gage sells for over $900 new too.

Anyone that needs a 6"-8 NPT is most likely going to buy new. The common sizes may sell. But highly unlikely you'll find buyers for the odd ones.

 

[MShaw]

If they are used in production they will wear beyond gage tolerances and still look good visually. Especially on aluminum. The 5/16-18 gage has a tolerance of .0003" on the pitch diameter.