This sort of orientation is usually best served by the use of a tooling ball, if there's no provision or possibility of using one then I'd suggest you construct a simple gauge/fixture to help yourself. Use of a known diameter rolled up against the angled surface yields the Z distance as well as the distance in the other axis (X or Y, whichever you have in the drawing). The critical thing here is how close you need to work to. You've stated that you need to work to microns, that means you need to have a diameter that can be well within (1/10) of your tolerance range.
As for using a mechanical edge finder (as opposed to an electronic one), there's the possibility of it digging into the surface as it slams into the surface with every rotation, mars the surface/unreliable numbers. Mechanical edge finders and wigglers should not be used when working closer than .127mm IMO as they just shouldn't be trusted. Work that close calls for the use of an indicator. If working to 10 microns (.0003937) a standard "tenths" indicator should be fine. If less than 10 microns you have many more factors to consider (temp, machine condition, set up accuracy, instrument accuracy, etc.). Since I don't know the workpiece, machine, or operation I can't suggest much more. I will state that if you've got 50 pieces of rework that are close tolerance you should obtain/make some close tolerance gauge/fixture to help yourself with. I hope this was of some help.  |