So to start off with, no I am not a machinist, mechanical/materials engineer, etc. Just someone who loves understanding the solutions to problems.
So I first found out about surface plates about a year ago after going on the "how do you make a precise part without a more precise part" quest.
Read up on surfaces plates and how they're made. Awesome, really clever, love it...
but.......
Last week I found some of the original videos I had watched on surface plates again, and at one point asked myself, "how do they know"?
I understand how the 3 plate method is able to produce a flat plane, but if someone was to just had you an arbitrary surface plate, how would you
determine it's flatness?
So this led me onto a new quest looking into the various ways surface plates are measured and graded, but frankly it seems like I'm right back at square one,
where all the parts used to calibrate a surface plate seem to require a part already just as precise if not more. It's almost like someone figured out how to
measure one independently, then everyone promptly forgot about it since they had a surface plate they knew was good.
So my question is, how do the devices which measure surface plates work without being calibrated against a surface plate of a known flatness,
or by being made out of parts which themselves had to have been calibrated against a surface plate at some point during their construction?
How did Maudslay & Whitworth do it? (I did search for this but wasn't able to find an answer).
To anyone who's just going to bark out "lasers/digital sensors", as far as I'm aware those do suffer from the same problem (if I'm wrong about that then please let me know).
Appreciate any answers/insight anyone can provide!
P.S. Just in case the tone of my post comes across the way I didn't intend it, I think this stuff is really amazing and fascinating, and I'm just frustrated that what seems
to be such a huge linchpin doesn't seem to get discussed that much.
So I first found out about surface plates about a year ago after going on the "how do you make a precise part without a more precise part" quest.
Read up on surfaces plates and how they're made. Awesome, really clever, love it...
but.......
Last week I found some of the original videos I had watched on surface plates again, and at one point asked myself, "how do they know"?
I understand how the 3 plate method is able to produce a flat plane, but if someone was to just had you an arbitrary surface plate, how would you
determine it's flatness?
So this led me onto a new quest looking into the various ways surface plates are measured and graded, but frankly it seems like I'm right back at square one,
where all the parts used to calibrate a surface plate seem to require a part already just as precise if not more. It's almost like someone figured out how to
measure one independently, then everyone promptly forgot about it since they had a surface plate they knew was good.
So my question is, how do the devices which measure surface plates work without being calibrated against a surface plate of a known flatness,
or by being made out of parts which themselves had to have been calibrated against a surface plate at some point during their construction?
How did Maudslay & Whitworth do it? (I did search for this but wasn't able to find an answer).
To anyone who's just going to bark out "lasers/digital sensors", as far as I'm aware those do suffer from the same problem (if I'm wrong about that then please let me know).
Appreciate any answers/insight anyone can provide!
P.S. Just in case the tone of my post comes across the way I didn't intend it, I think this stuff is really amazing and fascinating, and I'm just frustrated that what seems
to be such a huge linchpin doesn't seem to get discussed that much.