# Slide rule manufacture **URL:** \ **Category:** Factual Questions\ **Created:** [July 27, 2021, 8:56pm UTC](https://boards.straightdope.com/t/slide-rule-manufacture/947454 "2021-07-27T20:56:35Z")\ **Posts on this page:** 8\ **Page:** 4
**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\ **Post date:** [August 1, 2021, 7:52am UTC](https://boards.straightdope.com/t/slide-rule-manufacture/947454/61 "2021-08-01T07:52:29Z")
> [@Monty](#): > > Slight but related hijack: [here](http://www.antiquark.com/sliderule/sim/n909es/virtual-n909-es.html) is the virtual sliderule I use now that I can’t get a real one anywhere for a reasonable cost. That is … really poor. I hope that it’s an artifact of the virtualization: it looks like it’s based on a really really crap ‘demonstration’ slide rule. 3 \* 9 should be 27.0 I’ve got my dad’s 18" slide rule. He lost track of the 30" unit some time after he stopped using it. But even the plastic-fantastic rules we used in high school didn’t have obvious error like that virtual sliderule. ---
**Author:** ![Monty](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/monty/32/47_2.png) [@Monty](https://boards.straightdope.com/u/Monty)\ **Post date:** [August 1, 2021, 9:23am UTC](https://boards.straightdope.com/t/slide-rule-manufacture/947454/62 "2021-08-01T09:23:56Z")
I get 27 for 3\*9 on that site. ---
**Author:** ![Monty](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/monty/32/47_2.png) [@Monty](https://boards.straightdope.com/u/Monty)\ **Post date:** [August 1, 2021, 9:26am UTC](https://boards.straightdope.com/t/slide-rule-manufacture/947454/63 "2021-08-01T09:26:34Z")
Wasn’t the precursor to the Word War II torpedo data computer a circular slide rule, the is-was computer? I can’t find any photos of it. Maybe it’s my poor google ability. ---
**Author:** ![puzzlegal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/puzzlegal/32/3827_2.png) [@puzzlegal](https://boards.straightdope.com/u/puzzlegal)\ **Post date:** [August 1, 2021, 11:43am UTC](https://boards.straightdope.com/t/slide-rule-manufacture/947454/64 "2021-08-01T11:43:35Z")
> [@Dewey\_Finn](#): > > I graduated high school in 1984 and even then, slide rules were obsolete. But my high school physics teacher required us to obtain and learn to use a slide rule. Later we learned the reason was that doing so forces you to read a scale properly, estimate and think about orders of magnitude (is that result 100 or 1000). So kids were running around town asking stationery stores if they sold slide rules and of course almost none did. My brother was two years older and already had physics under the same teacher, so I inherited his. I think I still have it, though I don’t remember how to use it. Hey! I graduated high school in 1980, and until now, I’m the youngest person I’ve ever met who’s was required to use a slide rule in school. My chemistry teacher enforced an already-obsolete rule against calculators in class, and taught us after school to use sliderules. They were still available, then, but more expensive than cheap calculators. (The rationale of the rule was that it was unfair if rich kids could use a gadget not affordable to all.) Mine was a cheap injection-molded plastic thing, but i could usually get three digits of accuracy from it. I acquired a few more sliderules after that, mostly from places that still had stock knocking around. My favorite is a circular one that was given to my mom by the Chubb insurance company for some reason. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [August 1, 2021, 2:44pm UTC](https://boards.straightdope.com/t/slide-rule-manufacture/947454/65 "2021-08-01T14:44:25Z")
> [@Lumpy](#): > > Something fascinating that become obsolete even faster and more completely than slide rules: Edge-notched cards, a way of doing basic sorting and database search functions completely mechanically using index cards. This reminds me of a story one of my bosses told me, though about punch cards. As a grad student she was sorting the cards by a numerical value represented in BCD in several columns on the cards, and they had a machine that would sort the cards according to the height of the hole in a given column. She would set the machine to read the least significant column, the cards would appear in ten different bins, and she’d pull those stacks out in order and assemble them into one stack. Then she’d set the machine to the next column, and repeat. And the next, and the next. Each time, she’d get equal looking stacks in the bin, until she got to the most significant column. At this point, the output bin assembly looked like a bar graph of a Gaussian curve, which she found remarkable and pointed out to the professor, who happened to be there at that moment. He explained to her that that was pretty much the point of what they were doing. ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [August 1, 2021, 3:35pm UTC](https://boards.straightdope.com/t/slide-rule-manufacture/947454/66 "2021-08-01T15:35:25Z")
> [@Monty](#): > > Wasn’t the precursor to the Word War II torpedo data computer a circular slide rule, the is-was computer? I can’t find any photos of it. Maybe it’s my poor google ability. Here you go: [http://rnsubs.co.uk/articles/development/command-systems.html](http://rnsubs.co.uk/articles/development/command-systems.html) [![](http://rnsubs.co.uk/public/images/articles/command/command04.png) ](http://rnsubs.co.uk/public/images/articles/command/command04.png) ---
**Author:** ![JWT\_Kottekoe](https://avatars.discourse-cdn.com/v4/letter/j/3ec8ea/32.png) [@JWT\_Kottekoe](https://boards.straightdope.com/u/JWT_Kottekoe)\ **Post date:** [August 1, 2021, 4:38pm UTC](https://boards.straightdope.com/t/slide-rule-manufacture/947454/67 "2021-08-01T16:38:50Z")
I was once in an orthopedist’s procedure room and the doctor was interrupted about an issue with Mrs. Napier’s bones. I was amused and remarked on the irony of [Napier’s bones](https://en.wikipedia.org/wiki/Napier%27s_bones), but the doctor had no idea what I was talking about. ---
**Author:** ![Monty](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/monty/32/47_2.png) [@Monty](https://boards.straightdope.com/u/Monty)\ **Post date:** [August 1, 2021, 11:50pm UTC](https://boards.straightdope.com/t/slide-rule-manufacture/947454/68 "2021-08-01T23:50:43Z")
Excellent! [Previous page](https://boards.straightdope.com/t/slide-rule-manufacture/947454.md?page=3)