I love to use the slide rule, personally, but I get why most people have moved on to electronic calculators.
...except in one place: the kitchen. So much of kitchen work is about scaling proportions up and down. With a slide rule, this is literal child's play -- I have taught children to do it for me. You just set it once based on the key ingredient ratio and then you can immediately read off all other amounts without touching it again.
It is much easier than with any other calculation device -- as evidenced by the number of recipes I find where people hand-scrawl equivalent proportions onto them. They do that because they don't have a convenient way to scale up and down on the fly, so it's easier to make the huge effort (with an electronic calculator) once and then cache the result. (Only to have to do it again when you want to scale by a different amount.)
I honestly don't understand why a simple C/D scale slide rule with conversions on the back is standard kitchen equipment.
There used to be all sorts of cardboard "slide rules" that basically used slide rule-like principles to do calculations specific to some particular industry or function. I saw a bunch of them when I was in the oil business.
Kitchen can be a little harder with Imperial because you're often switching between units like fractions of cups to tablespoons etc. Must say I've never thought of using a slide rule of which I have a number--and I do usually use grams for weight.
> There used to be all sorts of cardboard "slide rules" that basically used slide rule-like principles to do calculations specific to some particular industry or function
You mean not just Europeans, but more than 95% of the planet's population?
(Also, I'm not sure I quite understand the semantics of "convert" used here)
Recipe is based on e.g. 5 eggs, but I want a smaller output so I want to use only 3 eggs[1]. I set the slide rule so that 3 is lined up under 5.
Then for any other ingredient in the recipe, say 7 tablespoons of milk, I look up 7 on the upper scale and read off 4.2 on the lower scale.
It doesn't matter which scale is upper or lower, and you don't have to keep track of whether you're multiplying or dividing, you just pick one to mean "recipe amount" and one to mean "actual amount". You anchor them against each other based on the critical ingredient, and then read off all other amounts. That's part of what makes it so easy to use even for children.
[1]: Or maybe I'm cooking to use up an ingredient about to expire, so I want to use all of my seven eggs, and so on.
Oh, that actually sounds really convenient. Next time I'm scaling a recipe by a factor other than 2, I'll get out the slide rule and enjoy the incredulous looks from everybody nearby. I can hardly wait!
I wish recipe sites just did that; enter a base for some product, get the rest based off percentages, rounded up to unit ingredients as best as possible
Most Pickett rules (once popular with secondary schools and still in abundance) are aluminum. Remove the slide, wash under warm water, lube with the nearest oil or fat, reassemble. Takes under a minute.
Usually I'd use Vaseline or a silicone lubricant, but expedient lubricants are fine if you'll wash it frequently and aren't trying to make multiple slide moves per minute.
The cursor requires a screwdriver if you really gunk it up (I'd be surprised), but it's still pretty easy. You don't need the cursor if you're just using the rule as a single-proportion lookup table, so you could take it off and put it away if it's a problem.
My only experience with a slide rule is a Hughes-Owens Versatrig, which is made from some bamboo-like material.
Knowing that metal slide rules were widely used makes me think that IKEA might come up with this “revolutionary” kitchen gadget in the next decade or two.
Also, unit price calculation when shopping — I did this for a while some years ago when I was actively collecting slide rules. And currency conversion — set to the current exchange rate it becomes a temporarily-fixed table.
I was talking with someone recently about computer floating point and now wonder to what extent the common use of slide rules and log tables influenced its development. I've read a lot of the early computing papers and only recall seeing discussion around whether or not the exponent (or characteristic) should be handled directly (i.e. floating point) or separately/implicitly (fixed point).
(And sliding back to rules, the A/B scales are analogous to one bit of float denormalization, although their primary purpose was extracting square roots.)
I think the most convenient way is the metric system. You had 1.5 desiliters of milk and 4 desiliters of sugar, but want to a half batch instead? Must be 0.75dl and 2 dl then
Metric or imperial doesn't really make a difference here.
Say the recipe is for five things and you want to make twelve.
You've got the same scaling problem no matter how you measure. You don't get "metric eggs", so solving "it needs two eggs for five so how many eggs for twelve" is the same.
Between 1963 and 1965, I had a good paper route (i.e. a set of customers to which I delivered newspapers each morning before school). I found myself flush with cash. I can’t remember exactly, but I think I was paid around $7 per week.
I bought four things with this fortune: a bike, a tennis racket, swim fins, and a fancy Pickett slide rule. I sill have the slide rule with its belt holster, it sits in my office next to my desk, a memento of my early interest in math and science.
I used the bright yellow slide rule along with my abacus a couple years later as a prop in a public speaking class to explain the difference between analog and digital computers. In high school, we are expected to use slide rules for chemistry and physics classes.
My trusty yellow slip stick also accompanied me to MIT where everyone used them. They were ubiquitous. I even had friends that owned circular slide rules. In that time, when only institutions could afford electronic computer, there were even cylindrical slide rules; their helical scales being long enough to obtain a fourth digit of precision.
I needed the slide rule one more time around 1988: it was for a popular Halloween party regularly hosted by a coworker at IBM. My costume was a taped together pair of heavy framed glasses, a shirt buttoned to the top, high water pants, pocket protector full of colored pens, and my well worn slide rule holster hanging from my belt. I saw L.L., an IBM Fellow, there and he said, “Hi Todd, didn’t you realize this is a costume party.”
I wonder how many niches still use slide rules today. I'm currently training for my private pilot license, and many of the calculations for flight planning are still done using what is essentially a circular slide rule [1]. Having grown up in an entirely digital era it took me a good long while to get used to it, but there's a level of elegance baked into this multi-purpose device that it's hard not to like it.
You're allowed to use an electronic E6B for the written test but IRL I think one's better off with the analog computer because it's harder to make a mistake with it like punching in a wrong number, and also because there's no battery to die.
I took one to a physics exam in college circa 1989, when intelligence had emerged that another class would come and spray us with buckets of water and there was no way I'd expose my previous HP-15C to that kind of risk. The professor looked at me funny but I went through without any issues.
I'd purchased it at the Ito-Ya stationery store in Ginza where they still sold Hemmi slide rules well into 1985 and I still have it, as well as my dad's and a couple of Concise circular slide rules from the MIT Museum.
>The pocket protector has been re-placed by a cell phone holster.
I thought there’s no way cell phone holsters were common as recently as the 2006 publish date of this article… but then I looked up a photo of me at work in 2006, and there I am, with my trusty blackberry holstered at my side.
I have an HP-35 (previous owner bought it new) mentioned in the article as "the death knell for the slide rule". The rechargeable batteries are long since gone and one of these days I'll get motived and try to replace them. It has very satisfying buttons, kind of like how old IBM PC keyboards feel.
It came with a metal case with lock and key. You would bolt the case to your desk and lock it. At $395 in 1972, I can understand why.
Calculators were considered too expensive to be required or allowed on exams since only few college students could afford them at the time.
So it was still slide rules only for me until about 1974 when the entry level TI's dropped below $100 and became permitted.
Slide rule use dropped like a rock.
When I started, students calculating during exams were doing the same mathematical tasks using the same physical tools they had been doing in those halls since the 1920's, a few years later they started doing about the same things they have been doing electronically ever since.
I wonder if anything else will come along after calculators, it seems like we've reached peak performance for that use case since there's sort of a cap to how much your tool can even be allowed to help given it's used during a test of your knowledge, not the tool's.
I grew up reading a lot of Heinlein. I always really got a kick out of reading about people flying around the solar system (and beyond) in nuclear powered ships, using slide rules to do the math for plotting their course.
I am old enough to have one and know how to use it. My dad gave me one when I was in high school and said I wanted to be an Engineer. When I went off to college in 1975, he gave me an HP-25, I still have it and it still works. But there is something special about a slide rule, the way it's made with such precision. I still have that one my dad gave me.
While some posit about going back in time with a crate of AK-47s, I always muddle about what might happen if you go back in time with a crate of solar powered scientific calculators. It may not have any impact whatsoever, but it's a curiosity of how much older engineering, finance, and/or economics may have been hampered by the speed, and precision, of calculation.
It's also interesting to think about that scene in Apollo 13 where half of Mission Control are working Lovells/Hanks math (on slide rules) and muse about how we managed to get to the moon (and back) with likely just 4 to 6 significant figures. Slide rules are most definitely limited in that way.
Slide rules are good for only around 3 significant digits, just a little more than most people’s mental math for multiplication. However, slide rules include scales for squares, cubes, trig, exponential, log functions and others.
All of these are inscribed as positions on logarithmic scales. In this manner, two scales can positioned to calculate products and quotients.
The scales, being logarithmic, are very compressed on one end, between 9 and 10 is only 5% of the scale while the interval between 1 and 2 occupies 30% of the scale (log 2 == 0.30, log 9 == 0.95).
If you can estimate measurements to a half millimeter on a precise ruler, on a one foot slide rule that corresponds to 508 divisions. Three significant digits requires 1000. With some careful interpolation while reading a slide rule it is sometimes possible to get 3 significant digits, especially in the range 1 to 2. It’s not possible to get 3 significant digits between 9 and 10.
Another limitation of slide rules is that there are no provisions for addition or subtraction. For this there were mechanical adding machines.
Notice too that all calculations are done with numbers in scientific notation. The scales start at 1 and end at 10. When calculating something like 447.8 * 1276, the slide rule is only able to calculate 4.48 * 1.28 for the user, and it gives a result like 5.73. The powers of ten have to be handled in one’s head. Furthermore, one has to understand trig well enough that having the sin only from 0 to 90 is good enough.
Because slide rules don’t give very precise answers, tables of logarithms were used for calculations requiring 4,5, or 6 digits of significance.
From what I recall that scene was mostly adding/subtracting numbers -- which you can't do on a slide rule. So the slide rules were artistic license in the movie. This also leads into the fact that they did have plenty of computers that helped get to the moon, although slide rules were used for a lot of quick calculations and estimation by the engineers. And my favorite slide rule, the Pickett N-600, was carried on several moon missions as a backup calculation device. (Here's a picture of it on a Gemini mission: https://commons.wikimedia.org/wiki/File:Buzz_and_his_pipe.jp...)
IIRC he figured out how far away the hacker was by putting an o-scope on the rs232 line and measuring the kermit protocol ack packet delay and that was a pretty amazing story.
It's been years since I've read it but recall it as a good read. He has another couple books as well but he admits he was wrong about various things in Silicon Snake Oil and the other book is sort of an ed-tech ant (about which he really wasn't wrong but not sure it brought a lot of new ideas.
Periodically on some of the slide rule discussion lists (there used to be one on Yahoo but now is on Groups.io), there is a discussion on the possibility of making new slide rules with modern processes. The discussions typically come down to several points.
First, there are a large number of vintage slide rules available for fairly cheap, and they clean up / restore fairly well. Typically the case (if it has one) will have someone's name written on it, which some don't like. On the other hand others like that it adds a bit of individuality and history to the piece.
Second, there was a run from Think Geek, but they were a bit less fun to use. I have one, the scales were printed on clear film sheets that got glued to a plastic body and the edges that slide aren't that crisp and a bit sticky. And there are a number of scales and arrangements for different purposes back in the day that this one doesn't have.
Third, their are new-old-stock rules available, but they command a premium price ($150 - $500 in many cases). And it is a dwindling supply. Plus, if you spend that much on it, chances are you won't want to use it as that would devalue it back to $20 - $30 territory because it won't be new in box anymore.
What I'd like to see is a build of the KeLon slide rule -- this was the last slide rule designed by K&E, but never got out of the prototype stage. There is one blurry photo of it, most of the scales are from other K&E rules but there is a unique "Constants" scale at the top that gives common gauge points (pi, sqrt(pi), HP/KW, etc). You can't make out the labeling but from the relative position you can figure out most of them. That would probably be the one that I'd copy if I try to hand make any.
I have a giant slide rule meant for teaching in my garage. The scales are off a bit, which I was surprised by. You'd think they'd be perfect, but no. 2x3 <> 6
I keep one on my desk at all time, I use it when we plan grocery runs, to guess how individual items cost when presented as "6 for 4.50", or when we do woodworking and my hands are covered in paint. A retired teacher gave me a bunch of those a while back, I never thought I'd use it so often. I really like the little Hemmi Bamboo ones.
I was taught slide rule basics in 8th grade. The teacher had one of those giant slide rules that was mounted above the blackboards. Then in freshman year of high school I got my first calculator (a Bowmar "Brain"). Every now and then I grab one my old slide rules and do some calculations, just for the fun of it.
Slide rules seem really cool! I'd like to acquire one for my desk. Anyone have recommendations for particular models or features? And where I can buy one? I'm hoping to get one in good condition, easy to use, and not to expensive. Bonus points if there is some cultural significance like the Pickett that the Apollo program used.
Depends on what you consider too expensive, really, whether you have any particular desired features, condition, whether or not you are likely to use it, your patience, and where you are (as different companies served different markets).
The common plastic high-school slide rules still turn up in thrift shops for a few dollars, priced by people who have no idea what they are, or in grab bags with dried-up pens and bent scissors. (The Acu-math on the cover page of the linked article is an example in this class.) On the other hand, particularly ‘collectible’ models like the Pickett N600-ES now sell for comfortably over $100 in any condition.
Personally I'd suggest one of the post-war Japanese-made engineering rules, since they have generally held up well. In the US the Post Versalog is the canonical example, but you can find many similar models under various names (in Canada, Hughes-Owens or Geotec) as well as the manufacturer's (Hemmi).
If you're at all interested in a circular slide rule, they are still available new from the last remaining manufacturer, Concise.
Too late to edit (sigh, HN), but although they haven't made slide rules for decades, “Hemmi Slide Rule Co., Ltd.” still retain the name! https://hemmi-inc.co.jp/english/
I was in a small town in North Carolina and stopped off at an antique store. There, I saw two slide rulers for sale, each for $15. I immediately bought both of them, and one of them was a Pickett N600-ES (of the four slide rulers I have [1], it's my favorite despite being the smallest).
[1] Three were bought at antique stores and one at a HAM fest.
I really recommend circular slide rules! Search "Concise circular ruler" on Amazon for a great quality but affordable slide rule. There's a couple of different ones so pick the one that has the functions you'll want.
Also, there's a bunch of watches with slide rules in the bezel. I have a citizen promaster on my wrist that is super handy for stuff like this.
I haven't looked in years. Mint condition good ones (K&E etc.) are going to be fairly expensive on eBay in all probability. If you just want a plastic slide rule that's perfectly functional though, they can be gotten for very little. You can read up on all the scales but most people just used C & D and maybe some trig.
Hemmi or Faber-Castell for linear slide rules, Concise for circular ones. The latter are still available on Amazon US or JP, I'd suggest the 300 or 270N.
I was in high school when calculators arrived on the scene. I still have several slide rules (one was circular so it would be more accurate :-) ). In the space of one year, slide rules completely disappeared. I stopped trying to show my kids how to use one when they kept looking at me like I was a caveman......
In about the mid-70s, electronic calculators went from something that was $100 for a very basic maybe 5 function calculator (and hundreds of dollars for an RPN HP) to maybe $100 for a functional TI scientific calculator in about a year. And that's mid-70s dollars. I got a discontinued HP maybe a couple years later for about the same amount of money.
>one was circular so it would be more accurate :-)
I have never used a slide rule, and I am missing the joke. Is that true? My assumption would be that humans are better manipulating a linear device than angles.
The longer a slide rule the more precise it is - you get mode decimal places. But it also become less convenient to use. That's where the circular slide rule comes in: a 4 inch diameter circular slide rule has the scales on its rim, which are 4 * 3.14 = 12.56 inches long, so it's equivalent to a 12.5 inch linear slide rule but more compact. That's how a Breitling wristwatch can include a usable slide rule - it's equivalent to a 6 inch linear slide rule on your wrist.
Also, in a linear slide rule you have to move the center scale left or right: to multiply 2 * 4 you move the slide to the right, but to multiply 3 * 4 you need to move it to the left (it "overflows"). With a circular slide rule you don't have that problem.
To build on the other answer. Precision is the word you want, not accuracy. My mother had an extra-long slide rule which sadly disappeared in some cleaning/move. But a circular slide rule can mimic linear length to some degree while staying fairly compact.
I have not used either but I assume it is possible due to it being easier to manufacture a pivot point with tight tolerances so there isn’t much play in the slide.
It's not really an accuracy problem AFAIK. But the precision (i.e. number of significant digits) is limited by the effective length of the scale (whether linear or circular) even if the manufacturing accuracy is perfect.
I bought a newer K&E probably 10 years ago. I brought it to college and even took it as a calculator backup to a few exams. It’s still on my desk in the office.
But I find it mostly stays on my desk. Operating a slide rule requires intentionality, and most of the time I really only want a quick answer. An RPN calculator is probably a permanent fixture on my desk.
I should get more use of my slide rule, though, just to practice that intentionality: sharpening the estimation skills needed to get the order of magnitude right, and the planning skills of what scales to use, what order, etc. so that the calculation is quick and the result is accurate. These skills are still quite useful in the present day, and few times do they come up as well as when using a slide rule.
I was taught to use a slide rule as a teenager when I used to help my father on weekends with his work, I'd get pocket money for my efforts.
My father, a mechanical engineer, used to bring home large plans (blueprints/diazo whiteprints) of new powerstations he was working on. The drawings were so big that the only place they could be fully opened and spread out was on the lounge room carpet. I'd lie down on my stomach spread out across the drawing with pencil, paper and slide rule in hand and cost the I-beams and RSJs against tables of steel types and prices (cost/ft).
The tool of choice back then had to be the slide rule as calculators weren't commonly available. In hindsight, for this job, the slide rule would still have been the better tool had I also had a calculator. For after checking the cost of a RSJ with a specific CSA (cross section), I did not have to move the rule's slide for every different length of same—all that was necessary was for me to look along the scale and note the cost for any given length. Pushing multiple buttons on a calculator in that circumstance would have been much more awkward.
It's a shame the slide rule has slipped from fashion because it has several significant advantages over a digital calculator, the first is that for repeated calculations where a variable changes each time, one doesn't have to enter a new value as all results are already calculated and displayed—one only has to read the result at the appropriate point on the scale.
The other is that slide rules use mostly log or exponential-type scales, they present instant graph-like visualizations of one's calculations. I've always thought that kids ought to be taught how to use slide rules for this reason.
With the demise of the slide rule I reckon we've lost that instant visualization. Electronic calculators provide much greater accuracy but lacking the visual/graphical-like representation their results are sterile (and in some situations less informative). We also see the same issue arising with the differences between analog/moving-coil and digital multimeters.
I reckon that both of these analog tools illustrate the virtue of approaching things from an analog perspective. No, I'm not resorting to Luddite mode and rejecting digital but rather we should take the best from both approaches. I think we were too eager to ditch analog technology and my view seems to be supported with the recent rekindling of interest in analog computers (as they're more appropriate in some applications due to their simplicity and that they require less power).
Incidentally, I still have my father's Faber-Castell 2/83N slide rule and my Hemmi Darmstadt that I used to do those calculations—both of which I still use.
...except in one place: the kitchen. So much of kitchen work is about scaling proportions up and down. With a slide rule, this is literal child's play -- I have taught children to do it for me. You just set it once based on the key ingredient ratio and then you can immediately read off all other amounts without touching it again.
It is much easier than with any other calculation device -- as evidenced by the number of recipes I find where people hand-scrawl equivalent proportions onto them. They do that because they don't have a convenient way to scale up and down on the fly, so it's easier to make the huge effort (with an electronic calculator) once and then cache the result. (Only to have to do it again when you want to scale by a different amount.)
I honestly don't understand why a simple C/D scale slide rule with conversions on the back is standard kitchen equipment.