Loply you don't need an indicator. An adjustable hard point will do. You just need contact both ways.
Besides, do you have an indicator that measures the 10 microns which is your goal?
The real question that has been missed all along, is not how to measure or get an angle, which you can do with many methods discussed and others as well, but how to rub and scrape it to that angle using contact methods, rather than measurement methods, which are the inevitable step in any mathematical determination of angle.
Sure, everyone knows Pythgoras theorem and owns a calculator, but once you've done the math how do you translate that without measuring? Sine bars and machined holes and pins are all measured somewhere along the production process -- whethere it is of the mill table calibration, mill tool size, mill movement, etc, and NONE of those are to my knowledge done to a 10 micron tolerance.
The whole essential of traditional hand scraping is a method which does not depend on measurement, but upon indicators of contact. We use math to do approximate work, and discard math in favor of contact and a contact indicator (blueing) to do extremely precise work.
I've already given a contact method which will, with a contact indictor, allow a person interested in a practical method, to scrape, and see non-contact areas. It will work as is.
I'm sure it could be improved upon (as most things can) with slight modifications to get work done more efficiently, though not necessarily more accurately. But most of what I'm reading here ignores the tolerance stated and the methods necessary to reach it. No system of measurement with a lower tolerance anywhere along the line of production will guarantee the tolerance required by the OP.
