Checking Table Flatness

[JPG]

Let's take a close look.

Using one area of an unknown flatness object to measure flatness of another area while relocating the initial area so as to measure other areas.

I totally agree with Ed.

Come on Dusty you of all people should know better.

This sounds sorta like what one does when using this tool to determine the proper adjustment of the blades on the cutter head of the jointer. The tool rests on one area of the outfeed table while measuring the height of the blade. It is then moved to another location to measure the height of the blade in a different location.

The only real difference, as I see it, is that the integrity of the outfeed table (the reference surface) is assumed.

If the tool is calibrated on the outfeed table of the jointer and then moved to main table, as the tool is moved around the main table in indicates the variances that we all know are there. Those variances are now being quantified.

Key words!!!!

Your original post suggested using the surface being 'measured' as a reference for measuring other areas of that same surface.

The jointer reference?(outfeed table) is a DIFFERENT surface.

Consider measuring the blade with the 'reference end' also sitting upon the blade.

[dusty]

Yes and I still intend to do that. The point that was intended is that the only difference is that the reference surface is known to be flat while the Main Table is known to not be. I expect dips and valleys. I want to quantify those deviations.

[JPG]

Good Luck making sense out of the observations.