5 ms·

The Origins of Precision [video]

51 points by gitgud 6y ago

canadian_tired 6y ago
If you prefer a book, take a gander at "The Perfectionists" by Simon Winchester. If you enjoy the pedantry of accuracy vs precision (or wish you did), this book is for you.
- aesthesia 6y ago
  I was disappointed with the book. There was not enough actual technical detail about achieving high levels of precision and too much journalistic fluff.
  - yetihehe 6y ago
    Yes, that book is more about people who made precision, not about technology (I didn't finish it yet, bought it after last article about precision on hn). But I'm not picky, it's nice read.
seiferteric 6y ago
He mentions that all bricks in a building are relative to the first brick... I am not an expert at all, but aren't bricks laid using a leveling line? And the mortar will provide some "wiggle" room to fix small mistakes?
- petertodd 6y ago
  You're absolutely right: https://www.youtube.com/watch?v=lORIZ1shRIM https://www.youtube.com/watch?v=lORIZ1shRIM Given that mortar is semi-solid, there's no way you could ever reliably get the same thickness of mortar without an external reference. Older tall chimneys are often visibly crooked in parts. I'm no chimney builder, but it's easy to imagine it being difficult to get the alignment perfect when you're trying to make an angled structure, high up in the air, using primitive tools. (remember that tall chimneys are narrower at the top than the bottom to save money, so you can't directly compare it to a vertical plumb-bob line: you have to offset each layer slightly from vertical) Equally, once the error builds up to the point where you can see it from the ground, getting the rest of the chimney back to true would be easy: just lay the next layers of bricks slightly offset until it looks right again. Results in an slightly ugly looking chimney. But a lot cheaper and faster than demolishing the crooked bit and starting over.
- dylan604 6y ago
  Also known as the cornerstone. Even though the mortar might wiggle, if the first stone is not correct,the building will not be in the correct spot.
jeffreyrogers 6y ago
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...
mikewarot 6y ago
One of the things he mentions is a chapter in Henry Ford's Book "Moving Forward" about the very practical need to be able to measure to a millionth of an inch... I highly recommend reading that chapter http://gutenberg.net.au/ebooks17/1700321h.html#ch14 http://gutenberg.net.au/ebooks17/1700321h.html#ch14
mauvehaus 6y ago
If you're into this sort of thing and in the Northeast, the American Precision Museum in Windsor, VT is worth a visit. Among other things, they have Bridgeport milking machine number 1. A lot of the original work in precision manufacturing was in the arms industry. Interchangeable parts in rifles were a huge deal when they came about: no longer did you need a skilled gunsmith to individually fettle replacement parts when a gun needed repair, you could swap one worn part for another in less time and closer to the action.
- tejtm 6y ago
  "Bridgeport milking machine" -> Bridgeport milling machine" in case your internal spell check does not fix it for you.

51 points by gitgud 6y ago

If you prefer a book, take a gander at "The Perfectionists" by Simon Winchester. If you enjoy the pedantry of accuracy vs precision (or wish you did), this book is for you.

aesthesia 6y ago
I was disappointed with the book. There was not enough actual technical detail about achieving high levels of precision and too much journalistic fluff.
- yetihehe 6y ago
  Yes, that book is more about people who made precision, not about technology (I didn't finish it yet, bought it after last article about precision on hn). But I'm not picky, it's nice read.

seiferteric 6y ago

He mentions that all bricks in a building are relative to the first brick... I am not an expert at all, but aren't bricks laid using a leveling line? And the mortar will provide some "wiggle" room to fix small mistakes?

petertodd 6y ago
You're absolutely right: https://www.youtube.com/watch?v=lORIZ1shRIM https://www.youtube.com/watch?v=lORIZ1shRIM Given that mortar is semi-solid, there's no way you could ever reliably get the same thickness of mortar without an external reference. Older tall chimneys are often visibly crooked in parts. I'm no chimney builder, but it's easy to imagine it being difficult to get the alignment perfect when you're trying to make an angled structure, high up in the air, using primitive tools. (remember that tall chimneys are narrower at the top than the bottom to save money, so you can't directly compare it to a vertical plumb-bob line: you have to offset each layer slightly from vertical) Equally, once the error builds up to the point where you can see it from the ground, getting the rest of the chimney back to true would be easy: just lay the next layers of bricks slightly offset until it looks right again. Results in an slightly ugly looking chimney. But a lot cheaper and faster than demolishing the crooked bit and starting over.
dylan604 6y ago
Also known as the cornerstone. Even though the mortar might wiggle, if the first stone is not correct,the building will not be in the correct spot.

jeffreyrogers 6y ago

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...

mikewarot 6y ago

One of the things he mentions is a chapter in Henry Ford's Book "Moving Forward" about the very practical need to be able to measure to a millionth of an inch... I highly recommend reading that chapter http://gutenberg.net.au/ebooks17/1700321h.html#ch14 http://gutenberg.net.au/ebooks17/1700321h.html#ch14

mauvehaus 6y ago

If you're into this sort of thing and in the Northeast, the American Precision Museum in Windsor, VT is worth a visit. Among other things, they have Bridgeport milking machine number 1. A lot of the original work in precision manufacturing was in the arms industry. Interchangeable parts in rifles were a huge deal when they came about: no longer did you need a skilled gunsmith to individually fettle replacement parts when a gun needed repair, you could swap one worn part for another in less time and closer to the action.

tejtm 6y ago
"Bridgeport milking machine" -> Bridgeport milling machine" in case your internal spell check does not fix it for you.