Distance from hole to hole

[[Ja...]]

First of all, there is no datums indicated on this print. I added side A and side B. If you had a drawing like the one attached (this is not the actual drawing), would you measure distance A perpendicular to side A and distance B perpendicular to side B because that's the side the dimension lines come from? What I use for an alignment will have an effect on the distance from hole to hole because these parts are far from perfect. It would make sense to just ask the customer what they want but unfortunately I can't ever seem to do that. I will propose the question to my supervisor and see where it goes since the customer is complaining about them being out of spec.

Dist_HoleToHole.pdf

[[Ma...]]

Hi,

first of all - consider posting inline image instead of downloadable pdf.

Next - are you measuring circle or cylinder?
Circles - in those cases I stick to Caliper distance.
Cylinders - trying to recall one of circular path into circle and then measuring their distance

[[Ja...]]

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This was meant to be more of a GD&T question than a Calypso question. Think of it as 2D. What side do you align your distance with when it is making a difference. Is there a general rule that would apply here or ask for more clarification?

[[Ma...]]

That highly depends on drawing

[[Da...]]

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One option would be to scan 2 cylinders and put them into Position - Bore Pattern Best Fit, then show additional information with the 2 distances.

[[Da...]]

When I stumble across something like that, I make a Bestfit of the holes with the tightest tolerances or the holes that I know are most important. That will minimize the positional error of those. If the other holes match their tolerances, everything is fine. Nominals must be known for this approach.

[[DW...]]

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In this instance, sometimes you have to tell the customer the challenges you are having based on their provided samples. Maybe side A and Side B have no importance to the part and they don't care about the perpendicularity of the sides to each other but perhaps mentioning it on a zoom call or email could get one of their engineers to add in some GD&T call outs solely for inspection purposes. Hopefully, you can explain to their engineers that you cannot find stable features for an alignment, and it is affecting (no repeatability) your results. I definitely get the hesitation to bring this up to a customer, because they may wonder if you know what you are doing. But if you can articulate to them the issues at hand, most of the time they will work with you because they need accurate, repeatable data. Best of luck.