true position errors?

[WINDRIDER]

what is best practice on TP? perp to center? and how do I use only 2 axis?

3.7 MR3

thanks

[Cryptonym]

When you dimension True Position under Axes the Auto box is checked by default (this will result in all 3 axis being displayed). Just check the two axis you wish to use. Or just dimension it with Auto checked and delete the one axis you don't want (highlight the line with the axis you wish to remove and hit delete).

As far as Pep to center goes I would say it depends upon what you are trying to check. Personally I don't use it. Here's what DMIS says:

"Deviation Perpendicular to Centerline
The Deviation Perpto Centerline check box determines whether PC-DMIS calculates the deviation perpendicular to the feature's theoretical centerline or if the deviation is calculated perpendicular to the direct X, Y, and Z values.

If selected, PC-DMIS calculates the deviation perpendicular to the feature's theoretical centerline, ignoring any deviation in the direction of the centerline.
If deselected, PC-DMIS calculates the deviation perpendicular to the X, Y, and Z values.
This check box is especially useful with sheetmetal points which may have approach vectors not oriented along the X, Y, or Z axis. This check box will allow the deviation to be found perpendicular to the approach vector."

[Matthew D. Hoedeman]

Think of it this way, PERP TO CL will give you the asme result AS IF YOU WERE CHECKING IT with a stab-pin in a fixture.