Non calibrated thread gauge rejection

[mkpash]

Hello gents,

We have recently rejected a part where internal thread M20x2.5-6H Left Hand thread is not acceptable.
When gauged using thread No-Go gauge, it enters as far as gauge will go (enters 6 turns).

Our Thread gauge is not calibrated, but effective diameters on gauge (18.367mm(Go) & 18.600mm(NoGo)) - when checked with calibrated thread parallels & micrometer seem OK.

My question here is will this be considered as a valid rejection?
Is it the correct way to check with external instruments the effective dia and make sure non calibrated gauge is OK to use?
In our case where we don't have a calibrated gauge, what other options do we have? - one that does come to mind is to borrow the suppliers calibrated gauge..

Regards,
Mustafa

 

[Gordon B. Clarke]

Hello gents,

We have recently rejected a part where internal thread M20x2.5-6H Left Hand thread is not acceptable.
When gauged using thread No-Go gauge, it enters as far as gauge will go (enters 6 turns).

Our Thread gauge is not calibrated, but effective diameters on gauge (18.367mm(Go) & 18.600mm(NoGo)) - when checked with calibrated thread parallels & micrometer seem OK.

My question here is will this be considered as a valid rejection?
Is it the correct way to check with external instruments the effective dia and make sure non calibrated gauge is OK to use?
In our case where we don't have a calibrated gauge, what other options do we have? - one that does come to mind is to borrow the suppliers calibrated gauge..

Regards,
Mustafa

"Seems OK" isn't OK. Start measuring your threads, especially if you have customers within the nuclear industry.

The correct "Go" dimension is 18.376 - not 18.367. That makes the pitch diameter tolerance 0.224mm. The NoGo thread on a gauge is never full profile so takes more care to measure than the "Go".

Get someone local with thread knowledge and get them to help and teach you. The "you" is plural.

If I was your customer and read your threads and posts I'd be looking for another supplier.

If your customer want documentation why don't you ask your supplier to supply it together with what you buy? That's what I'd call a no brainer.

 

[mkpash]

Blimey!
You're going through the mill with your suppliers...

When you've measured your NoGo, how near the (18.6000) size do you make it (you say "seems OK")?
Obviously you have to allow for your uncertainty of measurement and parallels inaccuracy and micrometer inaccuracy...

But no, if your sizes are good (accurate) i wouldn't say your rejection is invalid.
I would ask your supplier to visit with their gauge, and to check the parts with you and you could also measure their gauge as a check too.

But i would do all this BEFORE writing out a reject note!
As Bob said, it's a whole lot easier working with suppliers than against...

Thank you, your suggestions have been very positive. Was thinking along the same lines.

 

[Larry Dickman]

Seriously, how hard is it to send one thread gage out to be calibrated? If it comes back good, you can stick it in their face. If it comes back bad, your an idiot for having tried to use it.

 

[triumph406]

Hello gents,

We have recently rejected a part where internal thread M20x2.5-6H Left Hand thread is not acceptable.
When gauged using thread No-Go gauge, it enters as far as gauge will go (enters 6 turns).

Our Thread gauge is not calibrated, but effective diameters on gauge (18.367mm(Go) & 18.600mm(NoGo)) - when checked with calibrated thread parallels & micrometer seem OK.

My question here is will this be considered as a valid rejection?
Is it the correct way to check with external instruments the effective dia and make sure non calibrated gauge is OK to use?
In our case where we don't have a calibrated gauge, what other options do we have? - one that does come to mind is to borrow the suppliers calibrated gauge..

Regards,
Mustafa

You mustafa be joking

You rejected a part using an uncalibrated gage!! I'm amazed you'd ask whether that's acceptable or not.

It's not that hard to get your inspection equipment calibrated.


I'm assuming your facility has no certifications like ISO etc etc? An uncalibrated gage would be a serious non-compliance.

I had to invest in calibrated NPT pipe thread gages to prove that the pipe threads I tap are correct. I was getting pissed off when the customer would tell me the threads were either too deep, or not deep enough when putting in cheap Chinese fittings.

 

[triumph406]

Depends upon how you have written your QA manual...

There's probably zero chance you'd pass an ISO etc audit or qualification if your manual said it was acceptable to use un-calibrated inspection equipment in any situation.

It's safe to assume if a customer see's you have an ISO etc qualification that among other things you use calibrated inspection tools. I would at least.

Everywhere I've worked required the shop and inspection to have calibrated equipment as part of qualification. Now I did work for one place that did hide all the uncalibrated mics etc the shop guys were using during an audit.

 

[triumph406]

I know of at least 3x AS9100 shops where all SPGs are "reference only".
QUOTE]

Now I think about it, shop tools (mics,calipers,dti's) that weren't calibrated would get a "reference only" sticker in at least one place I worked.

That place could calibrate mics,calipers, dti's, but I would imagine thread gages, 3 point id mics were sent out for calibration.

They had a calibrated Mits CMM, nobody in inspection could use it, it was one of the programmers who did all the CMM inspection.

 

[Larry Dickman]

uncalibrated tools can be marked "Reference Only" and be used out in the shop. However, they CANNOT EVER be used for final inspection. (which is the case here)
Also, any uncalibrated gage that is not marked reference only, if found by an auditor, is grounds for an NCR.

 

[Delw]

I know of at least 3x AS9100 shops where all SPGs are "reference only".
QUOTE]

Now I think about it, shop tools (mics,calipers,dti's) that weren't calibrated would get a "reference only" sticker in at least one place I worked.

That place could calibrate mics,calipers, dti's, but I would imagine thread gages, 3 point id mics were sent out for calibration.

They had a calibrated Mits CMM, nobody in inspection could use it, it was one of the programmers who did all the CMM inspection.

uncalibrated tools can be marked "Reference Only" and be used out in the shop. However, they CANNOT EVER be used for final inspection. (which is the case here)
Also, any uncalibrated gage that is not marked reference only, if found by an auditor, is grounds for an NCR.

we just had an inspection at our place. The ONLY thing that is OK that is not calibrated are Gage pins and set up jo blocks marked as "for reference only". Any mics or caliper depth mic indicators drop indicators all have to be calibrated. They cant be on the floor period even if they are marked "for reference only"

 

[Gordon B. Clarke]

Mustafa, you give your occupation as quality engineer, your company supplies to a nuclear facility so you must be certified.

Given the above I'm at a loss as to why you are asking the questions you are.

I once experienced someone from a customer making an audit at a place where I worked. The questions he asked were similar to yours so I asked him what his profession was. "Engineer" he replied. I asked more and it turned out his engineering degree was for construction and not manufacturing. He'd never worked in a machine shop.