"primary point does not lie on secondary axis, tertiary not allowed"

I had a similar thing happen the other day. PC-DMIS seems to be sensitive about have a line defined as the secondary datum. For it to work reliably you need to go that extra step, as you discovered, and explicitly define the plane, perpendicular to A, that the line is being used to establish. A datum reference frame is 3 mutually perpendicular planes. While it is sufficient to only measure a plane, line, and point to have enough information to define these 3 planes it is still necessary to define the three planes for Xactmeasure to calculate the DRF reliably.

I discovered this the other day when I did the following:

- Established alignment with measured plane, line, and point.
- Measured an angled face that was at 28 deg. YZ rotation from datum A.
- Defined this new face as datum D
- Measured a hole normal to datum D.
- Tried to report this hole out to D|B|C
- Because datum B was a line and not a plane it would not allow me to do this and gave the error message you mention above.
- Changing datum B to a plane, or constructing a new line perpendicular to datum D and calling that datum B solved the problem. So the problem is that Xactmeasure looks at the vector of the line defined as datum B, this vector is not perpendicular to the primary datum, so it errors out.

I had a similar thing happen the other day. PC-DMIS seems to be sensitive about have a line defined as the secondary datum. For it to work reliably you need to go that extra step, as you discovered, and explicitly define the plane, perpendicular to A, that the line is being used to establish. A datum reference frame is 3 mutually perpendicular planes. While it is sufficient to only measure a plane, line, and point to have enough information to define these 3 planes it is still necessary to define the three planes for Xactmeasure to calculate the DRF reliably.

I discovered this the other day when I did the following:

- Established alignment with measured plane, line, and point.
- Measured an angled face that was at 28 deg. YZ rotation from datum A.
- Defined this new face as datum D
- Measured a hole normal to datum D.
- Tried to report this hole out to D|B|C
- Because datum B was a line and not a plane it would not allow me to do this and gave the error message you mention above.
- Changing datum B to a plane, or constructing a new line perpendicular to datum D and calling that datum B solved the problem. So the problem is that Xactmeasure looks at the vector of the line defined as datum B, this vector is not perpendicular to the primary datum, so it errors out.