Point vectors

[[Cl...]]

I have a 3 fluted drill. I need to get the inner web diameter. I'm trying two options. One using a 45° mirror with a Keyence. The second is with an O-inspect (w/rotary). 

For the CMM method I'm probing three points 120° apart and constructing a circle. However, I'm not sure exactly which type of point to use and how to calculate the

correct vectors. FYI, I will be using the Dotscan for these points. Any input would be greatly appreciated.

[[Ma...]]

I would trust that measurement.

Can you scan that as plane plane cylinder? Maybe circle instead of cylinder, close to edges.

[[Cl...]]

Not sure what you mean by plane plane cylinder? I'm using the arrowhead shaped plane on the upper right for rotation in space Z. This clocks the part.

The shaft OD is the primary datum. Tip is tertiary. I know the points have to be 120° apart, but I don't know which type of point to use or the correct vector

for those points (does it really matter)? Normally we use what's called a Mohawk. That not as reliable as we'd like. The vector should be 1, but relative to which rotation (angel) of the part. Remember I'm using DotScan and the rotary for this. I have to rotate the part three times to measure each point. Or am I over-thinking this?

Edited March 4

[[Cl...]]

For a little clarification this is what I'm after.

[[Cl...]]

Wrong picture really. I'm not after the ID diameter of a core drill, but rather the OD diameter of the web.

I was just going to delete it, but I don't know how to delete a post in this new forum?

Edited March 4

[[Ma...]]

I was thinking about this - I've understanded your needs