Measuring a recessed diameter

[[Do...]]

Hi everyone, I am relatively new to programming on Calypso and i'm looking for some advice. I have a part with a large thread, 2.5 NPT. There is a callout for the diameter under the threads that I would like to measure on the CMM. What would be the best way to go about this? I've attached a pdf to show exactly what i'm working with. My machine is a Contura with a RDS-CAA head. Part is currently measured with a 1mmx40 probe.

Ref.pdf

[[Cl...]]

Either a disc probe, or an "L" shaped probe. If you have an XXT, the disc probe option won't
be easy, as this sensor type does not (technically) support the disc. However, it can be done.

[[Ri...]]

It looks like you are trying to measure an undercut. As long as you can get a normal spherical stylus it shouldn't be too big of a deal.

I have no idea how you have this part orientated, but for the sake of this discussion, let's assume the thread is pointing to the +Z. I would create an L probe that has a stylus small enough to hit the cylinder of that recessed diameter. You will need to create a minimum of 4 indexes with the RDS - in this example let's say +Y, +X, -Y, -X with your L probe. Once you have those qualified, you can create a circle (or a cylinder, but it looks too short to get a stable reading) that has 4 individual circle paths each path using the respective tip to measure short arcs. Depending on how much clearance you have will dictate how much of an arc you can measure with each tip. It might only be 30 degrees, it could be as low as 10 degrees. Either way, you would do this for all tips. An important tip to remember is that the RDS is offset from the Z axis, so most likely you won't be able to rotate while inside of the ID of this part (I assume it's an ID). You will have to create either clearance or position points to get you in and out of the ID.

I hope this helps. Thanks.