7 ms·

There is a really great book called "Foundations of Mechanical Accuracy" that shows in detail (and with a lot of very good photographs/technical illustrations)

There is a really great book called "Foundations of Mechanical Accuracy" that shows in detail (and with a lot of very good photographs/technical illustrations) how extremely precise measuring tools can be built up from a simple flat plate. One of the most interesting things I've read recently.

mvidal01 6y ago
It's on Archive.org - https://archive.org/details/FoundationsOfMechanicalAccuracy https://archive.org/details/FoundationsOfMechanicalAccuracy
- CamperBob2 6y ago
  Archive.org is so weird. Henry Ford died in 1947, so Moving Forward is out of copyright (and consequently available on Project Gutenberg, as another post points out). Yet on archive.org I can only "borrow" an encrypted copy. Meanwhile, Foundations of Mechanical Accuracy was published in 1970 by Wayne R. Moore, who was presumably still alive at the time, so its copyright status is still very much in force... but archive.org says "Here, have a nicely-OCR'ed .PDF." I hope they're able to survive their present legal difficulties, but I'll be darned if I can see how.
petertodd 6y ago
While that's an excellent book, one of the things that I find fascinating about it is what it doesn't cover all that well: how do you make an accurate screw thread? The usual way you make a screw thread is by cutting it on a lathe. But the heart of a lathe is an accurate screw thread... How to making flat plates from scratch with the 3 plate method is relatively easy to understand. But screw threads have a much more complex geometry, with no obvious way of making one from scratch. They also have many more parameters to consider, including relative pitch accuracy, and absolute accuracy. As far as I can tell achieving accurate screw threads it something that took a huge amount of work by many different people effectively working together to get successively better and better threads, using each others' screw threads made using multiple techniques to average out errors. But I've never actually seen anyone describe from start to finish out to go from nothing to an accurate screw thread. It's not even clear to me that it's possible to do alone in a reasonable amount of time. Relevant: https://freechaptersinbooks.wordpress.com/2012/09/18/screw-thread-cutting-by-the-master-screw-method-since-1480/ https://freechaptersinbooks.wordpress.com/2012/09/18/screw-t...
- jeffreyrogers 6y ago
  Haha, I wondered the exact same thing when reading it. Same thing about the spindle. It talked about how you could measure how accurate a spindle was but not how one was constructed.
- aaronblohowiak 6y ago
  I imagine you can do this through gear reduction -- reducing the ratio of your leadscrew to the tool movement essentially reduces the inaccuracy of your leadscrew, iiuc. the percent error is the same, but you care more about absolute error than percent.
  - petertodd 6y ago
    That's a good idea. But I don't think it actually works, at least with the obvious way to do it. Suppose you have a lathe whose screw thread has errors in pitch such that the position of the middle thread is incorrect. With the right gears, you can use that lathe to cut a second thread with a different pitch. But regardless of what pitch you choose, the middle of that second thread will have the exact same absolute error in that position as the original thread. So you haven't actually improved anything. The best I can think of to improve the accuracy of a thread is to measure the thread against multiple length standards, and grind/lap away material by hand to bring the actual position along the thread length as close as possible to your length standards. However, as the number of length standards you can practically measure against is limited, you'll need to already be at a point where relative pitch error is small. Averaging out errors with a long follower nut is probably one way to do that.
    - aaronblohowiak 6y ago
      Why would the error the same in absolute sense instead of relative to the gear ratio?
      - aaronblohowiak 6y ago
        I will write up my idea later today.
thechao 6y ago
Currently priced at 2349.56$ with 3.99$ in shipping, on Amazon.
- SAI_Peregrinus 6y ago
  Or $150 from Moore. http://mooretool.com/publications.html http://mooretool.com/publications.html

mvidal01 6y ago

It's on Archive.org - https://archive.org/details/FoundationsOfMechanicalAccuracy https://archive.org/details/FoundationsOfMechanicalAccuracy

CamperBob2 6y ago
Archive.org is so weird. Henry Ford died in 1947, so Moving Forward is out of copyright (and consequently available on Project Gutenberg, as another post points out). Yet on archive.org I can only "borrow" an encrypted copy. Meanwhile, Foundations of Mechanical Accuracy was published in 1970 by Wayne R. Moore, who was presumably still alive at the time, so its copyright status is still very much in force... but archive.org says "Here, have a nicely-OCR'ed .PDF." I hope they're able to survive their present legal difficulties, but I'll be darned if I can see how.

petertodd 6y ago

While that's an excellent book, one of the things that I find fascinating about it is what it doesn't cover all that well: how do you make an accurate screw thread? The usual way you make a screw thread is by cutting it on a lathe. But the heart of a lathe is an accurate screw thread... How to making flat plates from scratch with the 3 plate method is relatively easy to understand. But screw threads have a much more complex geometry, with no obvious way of making one from scratch. They also have many more parameters to consider, including relative pitch accuracy, and absolute accuracy. As far as I can tell achieving accurate screw threads it something that took a huge amount of work by many different people effectively working together to get successively better and better threads, using each others' screw threads made using multiple techniques to average out errors. But I've never actually seen anyone describe from start to finish out to go from nothing to an accurate screw thread. It's not even clear to me that it's possible to do alone in a reasonable amount of time. Relevant: https://freechaptersinbooks.wordpress.com/2012/09/18/screw-thread-cutting-by-the-master-screw-method-since-1480/ https://freechaptersinbooks.wordpress.com/2012/09/18/screw-t...

jeffreyrogers 6y ago
Haha, I wondered the exact same thing when reading it. Same thing about the spindle. It talked about how you could measure how accurate a spindle was but not how one was constructed.
aaronblohowiak 6y ago
I imagine you can do this through gear reduction -- reducing the ratio of your leadscrew to the tool movement essentially reduces the inaccuracy of your leadscrew, iiuc. the percent error is the same, but you care more about absolute error than percent.
- petertodd 6y ago
  That's a good idea. But I don't think it actually works, at least with the obvious way to do it. Suppose you have a lathe whose screw thread has errors in pitch such that the position of the middle thread is incorrect. With the right gears, you can use that lathe to cut a second thread with a different pitch. But regardless of what pitch you choose, the middle of that second thread will have the exact same absolute error in that position as the original thread. So you haven't actually improved anything. The best I can think of to improve the accuracy of a thread is to measure the thread against multiple length standards, and grind/lap away material by hand to bring the actual position along the thread length as close as possible to your length standards. However, as the number of length standards you can practically measure against is limited, you'll need to already be at a point where relative pitch error is small. Averaging out errors with a long follower nut is probably one way to do that.
  - aaronblohowiak 6y ago
    Why would the error the same in absolute sense instead of relative to the gear ratio?
    - aaronblohowiak 6y ago
      I will write up my idea later today.

thechao 6y ago

Currently priced at 2349.56$ with 3.99$ in shipping, on Amazon.

SAI_Peregrinus 6y ago
Or $150 from Moore. http://mooretool.com/publications.html http://mooretool.com/publications.html