Measurement of nuts and screws

Hi Guys,

we are having trouble with convincing our supplier that our rejections for screws and nuts are valid.

basically we are using calibrated Thread Calipers as our main inspection instrument. However, when the same rejected screws are checked on a calibrated caliper at supplier, they are OK. My questions are as below:

what is the best/most thorough method of measuring screws out of below?
a. External Thread Caliper gauge,
b. Thread Parallels contacts (we currently don’t have thread micrometers),
c. Thread Pitch gauge
d. Go/NoGo Ring Thread gauge

Also for nuts we are using calibrated Go/NoGo plug gauge but even then it is not a valid rejection as per supplier.

How can we justify our inspections and convince supplier that our rejections are valid?

Regards,
Mustafa

 

Hi andy this is COTS M8 screws...Supplier is using the same methodology as we are using ->Thread Calipers and Plug Gauges
We did make a video. It clearly shows that the NOK parts measured on our caliper are OK on supplier's caliper
Both gauges certified to UKAS by the same company.
I am inserting the video here. Blue one is supplier gauge, black one is ours.


Now i don't know how to take this further..should we change our measuring methods?