Home shop metrology..

[Dan_the_Chemist]

I have a 9" x 9" x 9" granite angle plate I got off Ebay still in the felt lined box for $60 a few years ago.

I'll give you $75 ... that's a 25% profit !!!

[The Artful Bodger]

Vacuum tubes, I used to keep them but now when the motor goes to the landfill I just throw the tubes and hose in after it!

[Mcgyver]

Comparing the indicator reading on the face of the parallels to the back of the parallels, a proxy for the actual angle plate surface, you can again read any deviation from square. A zero change in the indicator reading "proves" the angle plate is square. And even if you can't contrive accurate parallels, you may be able to check the angle plate face against the opposite surface of a flat plate to get the same reading.

nice post.

The last check is what one does to create original squareness without multiple squares. You grind a 'master cube' instead of angle ( if scraping the angle plate works) you can make it to a tenth or so over six inches with the just the grinder, plate and indicator - ie no right angle fixture required. I don't think that can be done with an angle plate, except by scraping (that is without using multiple squares).

[dian]

putting two squares on the plate and checking with feeler gauges tells you nothing relevant to squareness. once you have established two parallel surfaces or the same diameter on a cylinder the surface gauge test is easy. i like to rotate the gauge and find the maximum (minimum?). i also smile every time i hear "a good machinist square". go and check on the tolerances. even a din 00 is horrible. i kike to buy things in pairs. my two din 00 squares produce a nice gap on the plate. making something square is difficult. my two din 00 beveled straight edges are just perfect, no trace of violet even with a strong light.

how do you measure lambda/10?