Finding Nominals for SPC Ports without CAD

I don't recognize what an SPC port is.

I googled it, and it brings up a grip of USB (and other) "Special Port Connections"... Since those special formats vary super widely from flat pins to USB to Mitutoyo proprietary and other brand-specific ports... There's not much i can say to help you, aside from suggesting you find whatever specification drawing for that component and do it the "old fashioned way".

That is: to define the nominals of your hits, using coordinate values based on the paper-drawing nominals for that port.

The only other alternative is to source the cad yourself and stick it in the model.  Here's some machining catalog for tooling SPC ports, which links the cad models of those ports on the site as an example: SPC Port Connectors On SUPERLOK USA (superloknorthamerica.com)

I am referring to the bushings where you would use a digital indicator to measure critical characteristics of a part. In my scenario it is a trim edge, but the indicator comes in slightly angled to the trim edge so a 50mm offset will not work for me. I appreciate the feedback.

Yup, still clueless, sorry.  SPC is an acronym for what? 
-Statistical Process Control?
-A physical connector with proprietary dimensional controls?
-Something else? You say a bushing?  Is this some kind of Probe stylus connection?

-Could you share a link, picture, napkin sketch, other detail to clarify what you are asking?

I never use FIXTURE CAD to verify a fixture.  By doing so, you are ASSUMING they designed the fixture correctly, and I've seen it many times where the fixture is either NOT made correctly, or made to the wrong revision of master product data.  I only use master product data. 

To do the SPC port, measure it as a cylinder and a plane (cylinder inside or on gage pins and the plane on the face). Intersect the cylinder and the plane for the first point.

Then create but do NOT measure a plane (using DCC features) on the part close to where the cylinder would intersect it.  Then intersect the cylinder and that plane for the 2nd point. 

Now, take the XYZ values for the 2nd point and using VECTOR point (DCC features), click on the part data where the point is, TYPE in the XYZ from the 2nd point and FIND that on the model.  Create that point WITHOUT measuring, then 3D distance the vector point and the 1st point to get the distance.  I did this all the time when "CMM DOESN'T MATCH THE FIXTURE" garbage to prove my numbers were correct and the fixture had issues.

I also only use master part data for checking anything else on the fixture, same reasons apply, master part data is master, not what someone did to make the fixture, simply use stock thickness to generate the points for the fixture check.

Thanks so much for your detailed answer Matthew. I will try this. I normally always use Part CAD to verify fixtures as I don't like to rely on the Fixture CAD. Occasionally I will get by using a master set pin and taking a vector point but I am required to measure the SPC Port bushing in this scenario. Thanks again for your help.

I would love to know as well. It's really hard to tell what acronyms mean what these days without it being previously defined first like "as known as", AKA

SPC ports are nothing more than a hunk of metal on the fixture, with a bushing in it, with the face of the bushing to be a set distance from a perfect part (for some strange reason, this distance is 31mm almost all of the time) that you stick an indicator in that presses up to the face of the bushing, and the tip touches the part to give you a deviation of the part.

SPC = STATISTICAL PROCESS CONTROL.

looks something like this: