Hello Forum.

I hope I posted in the correct area.

I have been lurking for a while now, and have found this site to be VERY infomative.

But now I must ask for some assistance.
We have been recieving some taps manufactured specificly for us. We have had some issues with the measurment of the "hook angles"

We do have a video inspection machine that is more than adequet for this task. However, there seems to be some disagreement as to the correct method for measuring the hook angles.
We think we are doing this correctly, but the numbers the we get do NOT agree with what the manufacturer insists that they are.
We have provided inspection reports to the supplier, but they say when they populate their "program" with the values that we recorded, that the hooks angles documented on our inspection report are "impossible"
Apperently, they have some kind of computor/CAD program or spreedsheet. They have sent us their reports, and they are very different from ours(as far as the hook is concerned)


So, I am here to ask if anyone has ANY illustrations/pictures for the correct method of inspection for these hook angles. or point me to a website that may provide additional clarity to this matter.

Our inspection machine can be a comparitor/video camera/CMM
It is very sophisticated, and I think the supplier is measuring by mechanical means.

I hope this was informative enough that you all get the idea.

Thanks in advance for any information you all may provide.
Cheers,

Kevin

Hello Forum.

I hope I posted in the correct area.

I have been lurking for a while now, and have found this site to be VERY infomative.

But now I must ask for some assistance.
We have been recieving some taps manufactured specificly for us. We have had some issues with the measurment of the "hook angles"

We do have a video inspection machine that is more than adequet for this task. However, there seems to be some disagreement as to the correct method for measuring the hook angles.
We think we are doing this correctly, but the numbers the we get do NOT agree with what the manufacturer insists that they are.
We have provided inspection reports to the supplier, but they say when they populate their "program" with the values that we recorded, that the hooks angles documented on our inspection report are "impossible"
Apperently, they have some kind of computor/CAD program or spreedsheet. They have sent us their reports, and they are very different from ours(as far as the hook is concerned)


So, I am here to ask if anyone has ANY illustrations/pictures for the correct method of inspection for these hook angles. or point me to a website that may provide additional clarity to this matter.

Our inspection machine can be a comparitor/video camera/CMM
It is very sophisticated, and I think the supplier is measuring by mechanical means.

I hope this was informative enough that you all get the idea.

Thanks in advance for any information you all may provide.
Cheers,

KevinThe following may or may not be helpful.

When I was in the high-tech machining business, we sometimes had customers provide specifications THEY were unable to inspect/confirm simply because they did not have the proper inspection instruments or because their personnel were untrained.

Conversely, we also had some customers with even more sophisticated equipment and inspectors than we had.

Our solution was to collaborate with customers on the method and instrumentation available to us both so we could each replicate the other's results IF, and only if, any question arose about nonconformity.

On at least one occasion, we and our customer sent representatives and the suspect parts to a third party who would inspect them and make a judgment call, providing a feedback report on how to resolve the discrepancy between our inspection systems. I want to stress that the parts in question were usually compatible with form, fit, and function of mating parts, merely that the different inspection systems and techniques were at variance.

In defense, we implemented a policy of making agreement on inspection methodology and instrumentation an important part of contract review.

Hook angles are tricky to measure - I often had difficulty deciding if the hook was positive or negative, let alone the actual angle of the hook.

For folks not familiar with the hook angle on the tap, here is a definition and I have added a pdf file with a drawing.
HOOK ANGLE
The inclination of a concave cutting face, usually specified
either as Chordal Hook or Tangential Hook.
Chordal Hook Angle: The angle between the chord
passing through the root and crest of a thread form at the
cutting face, and a radial line through the crest at the
cutting edge.
Tangential Hook Angle: The angle between a line tangent
to a hook cutting face at the cutting edge and a radial line
to the same point.Complicated, huh?

I never had the task of actually measuring a hook angle, other than to make a determination of positive or negative. I'd be interested in seeing a step-by-step description of the instruments and techniques which both customer and supplier use.

Thanks for the reply Wes as well as the attachment.

We have already made the determination that the inspection proceedure for this feature needs to be performed the same. Whether its our supplier adopting our technique or us adopting their technique.
We have pulled some screen shots from our video inspection machine and are forwarding them to our supplier, along with the proccess/technique steps used inhouse for inspection of this feature.

I hope this will be resolved soon, its making my head hurt.

Thanks again.

Kevin