Slide rules - Page 1
Forum section: electronics / general

author: Johnboy
author_rank: Regular Contributor
timestamp: October 05, 2019, 05:20:53 pm
content: I'm aware that some of the older forum members look at these threads to offer advice to beginners, so I felt this might be a good place to begin a discussion of this topic. Dave's recent mailbag video addressed a hybrid analog/digital calculator, made by the German company Faber-Castell in the 1970's. Those with an interest in following this thread might take a look at that video first.The slide rule, a mechanical parallel computer, antedated the common use of the handheld electric calculator. Before the advent of the calculator, slide rules were used as a check on mental/pencil/paper calculations.In my self-study of electronics, I started as many have, using the most recent available technology. Modern computer simulations of circuits and inexpensive chipsets in multimeters, as just a couple of examples, have mainly replaced the older tools used by previous generations of engineers to develop their understanding of circuit theory and operation.After a lot of self searching about how I wanted to master the basics, I created a second "caveman" lab, mainly using older, used, analog equipment and supporting texts to try to recreate the electronics learning experience of the early 1970's in the United States. My main tools are an analog VOM, a CRO, a slide rule, compass, protractor, triangles, and prodigious amounts of graph paper to document my understanding as I go.One of the most interesting aspects of the "old way" of learning the basics was the emphasis on estimation of mathematical solutions to real world problems. Before digital technology was everywhere, engineers often "overbuilt" their bridges, buildings and equipment as a result of having to make quick design decisions using approximations of formulae without the precision and accuracy that modern computing has made ubiquitous now. Erring on the side of caution produced thicker walls, safer distances, and larger workable tolerances. The relatively "hamfisted" approach also produced some gargantuan design mistakes, of course, but I'm not mainly interested in the discussion of the obvious, glaring limitations of these tools on their operators.Cleveland Institute of Electronics (among many others) offered electronics courses designed around the use of the slide rule as a computing instrument. As the digital versions of calculators, multimeters, and even oscilloscopes replaced their analog counterparts in the workplace lab and field, the older tools were not-so-gradually phased out of the educational environment as well.My questions to those of you with the background, education, and/or work experience in the use of the slide rule (worldwide, not just in the US) are these:1. Which slide rule (manufacturer, model) did/do you use, and why? Did you select it yourself based on application, or was it chosen/required by the school, academy, or military branch?2. Which texts did you use in concert with this tool during your education?3. What things do you still occasionally use them for, if at all? If you use them regularly, is it merely out of habit or are there certain calculations for which you prefer them to having to punch buttons on a digital calculator?4. What benefits do you feel you may have gained from learning how to use them?Any and all replies would be greatly appreciated, as I'm trying to keep detailed notes on my own progress and would like to hear how others may have fared in similar, although less-self-imposed, surroundings.

author: IanB
author_rank: Super Contributor
timestamp: October 05, 2019, 05:31:04 pm
content: Quote from: Johnboy on October 05, 2019, 05:20:53 pmThis is not quite correct. Before digital calculators were available, slide rules were used to do actual calculations, not just to check results. They were the equivalent of the modern pocket calculator. However, since digital calculators were superior in every way they rendered slide rules totally obsolete. Slide rules today are only a curiosity and have no practical use.Interestingly, digital pocket calculators have since been rendered almost totally obsolete by personal computers. The software available for personal computers is far faster and more capable than anything calculators can do.QuoteThe "not so gradual" bit is rather true. Pocket calculators appeared when I was in high school. They wiped out slide rules overnight. One year slide rules were taught and used, the next year they had vanished.

author: rstofer
author_rank: Super Contributor
timestamp: October 05, 2019, 06:19:35 pm
content: Well, shoot, I made it through undergrad with a slide rule. Probably K&E Log-Log-DeciTrig. I have a different 10" I got from eBay but I still have my original 6" K&E. FWIW, the HP35 came out in my junior year of undergrad. No way could I afford it.We went to the Moon using slide rules. Yes, there were many computers involved but EVERYBODY had a pocket slide rule. When you absolutely, positively, needed an answer right now, you certainly didn't have time to write a Fortran program and submit a batch job.Here's what I learned: I automatically change to E notation with 1 digit to the left of the decimal point. No problem multiplying such numbers in my head but the slide rule brings another digit or two. But the real trick is keeping track of the powers (or decimal point) in your head. I still do that today! RC circuit 10k resistor, 100 nF capacitor: 1.0E+4 * 1.0E-7 so the result is 1.0E(-7+4) or 1.0E-3 so Tau = 1.0 ms. Useful...I provided a brief introduction to slide rules to my grandson, the BSME student. I don't imagine he will use it for any course work but he did get some laughs out of it.If calculators are obsolete, how come I have an HP41 emulation on my laptop/tablet(s) and an HP48GX on my desk. The GX is about as far from my keyboard as is my mouse. It's just over on the left and I use it constantly!And in no way are any of these calculators the equivalent of Octave or MATLAB.We've come a long way since I graduated in '73.

author: MarkF
author_rank: Super Contributor
timestamp: October 05, 2019, 06:20:54 pm
content: None of that back-and-forth crap.Round and round we go.We got these in high school chemistry class, 1970s (teacher choose them).

author: HighVoltage
author_rank: Super Contributor
timestamp: October 05, 2019, 06:54:37 pm
content: I grew up in Germany and went to the University in the 80s and everyone was using calculators and of course me as well. But I had always mby mini pocket slide rule with me, because it was much faster than any calculator, to get a good idea of the results.I am still using it these days from time to time, just for fun.Faber-Castell was most likely Germans best known brand for slide rules but they were large and they did not have a mini one at the time, when I was looking. So, a friend introduced me to the very well made USA slide rule in the pictures below.

author: ArthurDent
author_rank: Super Contributor
timestamp: October 05, 2019, 07:05:32 pm
content: Johnboy - "3. What things do you still occasionally use them for, if at all?"My Pickett slide rule still makes one hell of a back scratcher.

author: Gyro
author_rank: Super Contributor
timestamp: October 05, 2019, 07:10:30 pm
content: I remember when we were allowed to take slide rules into exams but not calculators. I didn't bother - I was so inept at using the things, it wouldn't have done me any favours!P.S. I bought my maths graduating nephew an early '30s Japanese Sun Hemi Model 1 slide rule as a gift a while back. They had the unique feature of using the dimensional stability of Bamboo ply (what else). It had a really smooth action and zero play, even after all these years. A thing of mathematical beauty.https://www.sliderulemuseum.com/Hemmi.htm

author: rstofer
author_rank: Super Contributor
timestamp: October 05, 2019, 07:37:11 pm
content: There should be a "National Slide Rule Week" where participants agree to leave their computers and calculators dark and use only slide rules. It would be fun! If it ever becomes real, I'm all in!Of course, I would need to learn how to use most of the scales all over again. I remember C & D but I'd have to think about the others.

author: Gregg
author_rank: Super Contributor
timestamp: October 05, 2019, 07:42:28 pm
content: From my experience, a slide rule was a solid representation of how the rules of math related to one another. The emphasis on math estimation and the actual significant numbers necessary was a true revelation of real world uses for math. The linear layout of logarithms helps give a mental image of how logs work. The fact that a slide rule user has to mentally keep track of the decimal point placement certainly helped with learning how a calculation works. An early revelation was a high school physics teacher that stated “You don’t have to memorize things verbatim if you know how to derive them”; a lesson I have found useful my entire 70+ year life.1. Kuffel & Esser Deci-lon 5 was and still is my favorite slide rule. It has expanded log scales if more significate numbers are needed. The sliding scale folded at pi is very handy. I also have a 10 inch version, but found it unnecessarily bulky for the little bit better resolution; besides only the truly nerdy carried around 10 inch or longer slide rules. The 10 inch did come with a nice hardbound instruction book, however.There were many manufacturers of slide rules in the 60’s. Post made a bamboo rule that many students bought on recommendations of instructors. I don’t know if humidity changes affected the accuracy, but they certainly affected the sliding smoothness. Pickett made aluminum ones that tended to gall on the sliding joints. I preferred the slide action and adjustability of the K&E.2. I don’t remember the text books at all. I was financially strapped as a student and tried to share texts, buy used and sell at the end of the semester.3. I confess, I really only use my slide rule(s) to keep a little bit in practice and to show them off to younger people. It helps to know how to use one if you really want to impress someone.4. I feel I gained a better understanding of math from slide rules as stated above.It is like the difference between an analog volt meter and a high impedance digital volt meter. The digital will tell you that there is an AC voltage on a wire that runs parallel with powered wires when the analog will read zero; the voltage is there but it isn’t significant.

author: basinstreetdesign
author_rank: Frequent Contributor
timestamp: October 06, 2019, 12:29:03 am
content: I have had mine handy ever since I bought it in 1970 even though I never use it anymore. It got me through the first two years at Waterloo. I could be seen legging it across the campus with it swinging from my belt in its scabbard and build-in belt loop. It was one certain way to tell an engineering student from all of the others. It is a Dietzgen Cat # B-1734 and although it sounds German it has "MADE IN JAPAN" stamped on it.Even it still works perfectly and even though I regard it with fondness I always rely on one silicon-based calculating instrument or the other to do the actual work. I admit that I have gotten lazy about keeping track of the decimal point.I have mentioned it a couple of times in one Reddit forum or the other to those just discovering electronics and it has never been met with insults but always with admiration.

author: don.r
author_rank: Frequent Contributor
timestamp: October 06, 2019, 01:31:28 am
content: My father worked for Keuffel and Esser in Montreal and gave me my first slide rule when I was 10. My math skill wasn't up to scratch to use it properly until I was about 15 and by then (1979) calculators started to become mainstream.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: October 06, 2019, 03:36:48 am
content: 1. My favorite slide rule was my K&E log log dupli trig rule. I had won a cheap plastic slide rule in middle school, chose this one among the styles available at the college bookstore my freshman year. Reasons for selection. Smooth action and wide range of functions.2. The slide rule was and remains faster than a pocket calculator for the things it can do. The HP-35 came out when I was a senior in college and I couldn't afford one. After a masters degree and entering employment I regularly had races with HP equipped colleagues. They could only win by going for more significant figures than the data contained. The speed occurs because digit entry is essentially serial on a calculator, but is largely parallel on the slide rule.3. Remember that for all the things that slide rules can do, the one thing they can't do meaningfully is add and subtract (few if any slide rules come with two linear scales.). This is one of the reasons that calculators took over. Another is bulk. The pocket calculator is easier to carry around than a slide rule large enough for engineering precision. Still another is the mystique. I can't count the number of times in a group discussion that I ended an argument by holding up a calculator with a number on the screen. In some cases I had merely typed the number in after doing the rough calculations in my head.4. I do agree about how rapidly the slide rule disappeared. It was a little slow at first because HP's price tags were significant even on an engineers salary, but when TI came out with the TI-59 the game was over within a year.5. Slide rules hung on for a while longer in specialty applications. I was still using my GE Infrared Slide Rule when I bought the programmable HP-65, my third scientific calculator. But it wasn't long before I had the 65 programmed to do the job of the IR rule, but better. I understand that other fields, perhaps including aviation navigation, had similar experiences.

author: Tom45
author_rank: Frequent Contributor
timestamp: October 06, 2019, 03:59:38 am
content: I was in college in the 60's and only used slide rules. Calculators didn't start to appear until several years after I graduated from college.1. Which slide rule (manufacturer, model) did/do you use, and why? Did you select it yourself based on application, or was it chosen/required by the school, academy, or military branch?I used K&E slide rules all through engineering school. Started with Log Log DeciTrig and then later the DeciLon came out and I switched to it. My father was a civil engineer and I had his old K&E Log Log Duplex slide rule when I was in high school. So I grew up with K&E and stuck with what I was used to using. I don't remember any guidance from the school on what slide rule to use. But that was over a half century ago, so they might of said something and I just don't remember.I think K&E slide rules were in the majority at school, but second place was the metal Pickett slide rules.2. Which texts did you use in concert with this tool during your education?No texts. Engineering Fundamentals class my freshman year might have covered slide rule usage, but I don't remember. Same excuse, that was over a half century ago. In any case, I was fluent in slide rule usage before entering university. All self taught.3. What things do you still occasionally use them for, if at all? If you use them regularly, is it merely out of habit or are there certain calculations for which you prefer them to having to punch buttons on a digital calculator?Since the arrival of eBay I've acquired a considerable collection of slide rules from around the world. Back in the slide rule era, I really only knew about K&E, Pickett, and Post.I don't use them now other than for the enjoyment of trying out different models from my collection now and then.Using a slide rule to look at proportions is still hard to beat with any other method.4. What benefits do you feel you may have gained from learning how to use them?Before you do a calculation with a slide rule you need to understand the calculation well enough that you can predict the answer to better than an order of magnitude. The slide rule gives an answer to a few places but the user has to supply the actual placement of the decimal point and exponent. That was a big deal in engineering classes that was drilled into us. We should have a good feeling for the likely result before picking up the slide rule.Besides knowing about what to expect for the answer, we also were expected to know how many significant digits made sense in the result. A calculator can give a result to 12 places of a calculation that had measurements to 2 or 3 places for the inputs to the calculation.My senior year in EE I attended a one term seminar course where the class designed a digital calculator. We didn't actually build anything, just did the logic design. It wasn't too many years later that the first pocket calculators arrived.

author: vk6zgo
author_rank: Super Contributor
timestamp: October 06, 2019, 04:50:13 am
content: Quote from: IanB on October 05, 2019, 05:31:04 pmThey are also huge, compared to a pocket calculator, & take time to set up for a quick calculation.A pocket calculator "is ready to go" & you have the answer whilst your colleague is still finding the calculator "app"!QuotePS, I had a slide rule, but never became competent in its use---I used Log Tables most of the time, instead.

author: AG6QR
author_rank: Frequent Contributor
timestamp: October 06, 2019, 05:49:16 am
content: I used a slide rule in high school, but basically because I was curious about how they worked and wanted to learn on my own. I was in high school when the TI-30 scientific calculator was first introduced, and it, along with similar models from other manufacturers, pretty much made slide rules obsolete. But there was still a huge slide rule, probably 8 feet long, on top of the blackboard in my chemistry/physics classroom. It wasn't part of our curriculum, but the teacher demoed it once or twice, and that was enough to spark my curiosity and learn how to use one on my own.In the early 1990s, I took flying lessons, and the most popular navigation computers in common use by pilots were still variations on the E6B circular slide rule. in fact, you can still buy them.https://www.sportys.com/pilotshop/full-size-e6b-flight-computer.htmlUsing one of these made navigation and fuel consumption calculations easy. And there are no batteries to wear out.For a while, I wore a watch with a miniature version of the E6B circular slide rule around the bezel. At the time, I was no longer flying, but it was still handy for calculating gas mileage or ETA during car trips, along with any general type of ratio problems.When you only need two digits of precision, a slide rule is generally quicker to manipulate than a calculator or smartphone.I have it on good authority that the E6B style circular slide rules will still be in widespread use in the 23rd century.

author: WA1ICI
author_rank: Contributor
timestamp: October 06, 2019, 04:46:35 pm
content: The HP-45 calculator came out when I was a junior in engineering school. It appeared to be a magical device at the time! I'm still hooked on RPN.Before the calculator, I used an aluminum Pickett slide rule. Since you had to manually figure out the exponent, you had to reallythinkabout the calculation, which, although slowing you down, keeps you focussed on what's going on. With a calculator, it is garbage-in, garbage-out.No one has mentioned log tables yet.- John Atwood

author: CatalinaWOW
author_rank: Super Contributor
timestamp: October 06, 2019, 04:58:17 pm
content: Log tables and trig tables. I spent many hours in my early days interpolating five digit log and trig tables and doing the associated arithmetic on a desktop mechanical adding machine. It was how the calculations that mattered were performed. Slide rules were for the quick and dirty answers, preliminary designs and the like. Thinking back on it I probably solved ten times as many problems using a slide rule, but spent ten times as much time on those relatively few occasions when precision was needed.Scientific calculators were slower for the quick problems, but not by much, only percentages difference and took the same time for as much precision as anyone could use. That comment about log tables triggered that memory and is surely the real reason calculators took over so quickly.

author: HighVoltage
author_rank: Super Contributor
timestamp: October 06, 2019, 05:47:27 pm
content: Quote from: CatalinaWOW on October 06, 2019, 03:36:48 amFor that we used theSumax Addimult.One side for addition and the back side for subtraction.Made out of brass with a brass pen and worked very well before calculators.The simplest mechanical calculator I own.

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 06, 2019, 07:09:51 pm
content: https://en.wikipedia.org/wiki/Pascal%27s_calculator

author: ferdieCX
author_rank: Regular Contributor
timestamp: October 06, 2019, 11:22:59 pm
content: I learned to use the slide rule when I was 15, and attended the basic level of technical High School. I used an introductory book that was written by the technical University.One year later, I got this Aristo Studiolog 0969 that I used up to 1982. The obtainable precision was enough for the then usual 5% tolerance components.

author: Canis Dirus Leidy
author_rank: Regular Contributor
timestamp: October 07, 2019, 11:51:02 pm
content: Quote from: Johnboy on October 05, 2019, 05:20:53 pmNot really. The slide rule was used for calculations where speed was important, with moderate accuracy requirements (the “standard” 25-cm ruler provides the accuracy of the result up to 3 digits). The"Iron Felix"was much more accurate, but it could only perform four basic arithmetic operations (no trigonometric functions, no logarithms, no arbitrary powers, etc.). As for electronic pocket calculators... The slide rule cost around 4 rubles. For comparison: the simplest (basic arithmetic only, some models have memory and few additional operations like square root and 1/x) calculators cost (in the mid eighties) 20-40 rubles (comparable to a hungry student scholarship), scientific calculators cost 50-70 rubles and price of programmable calculators was 80 and more rubles (almost the entire monthly pay of a freshly graduated engineer at first job).P.S. Grandfather's slide rules:I used them for a while (in Nineties), but it was mostly a show off.

author: Circlotron
author_rank: Super Contributor
timestamp: October 08, 2019, 12:29:51 am
content: As well as general purpose slide rules there are probably many specialist ones. Here is one used by the drag race crowd for estimating vehicle performance.https://www.hotrod.com/articles/speed-rpm-gear-ratio-tire-size-formula/#moroso-analog-slide-rule-style-calculator-detail1

author: edy
author_rank: Super Contributor
timestamp: October 08, 2019, 04:39:58 pm
content: I have a rotary slide rule on my Seiko watch... I actually use it sometimes. The bezel rotates. Besides having the normal multiplication capability, there are labels for certain ratios for conversions of units (KM/mile, liters/Gallons, Lb/Kg, etc):To be honest, I'd love to get my hands on an old slide rule if anyone is planning to dump theirs. I think it is an art and skill that has been lost but still very interesting to learn and keeps your mind sharp, making sure you are keeping track of the order of magnitude/places when you are multiplying or dividing.

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: October 08, 2019, 11:57:02 pm
content: Quote from: edy on October 08, 2019, 04:39:58 pmHello edy, I may have at least 1 and up to 3 standard slide rules. They would be in boxes stored at my parents house and it will take a few days to check, as I am visiting them tomorrow. I will PM you if I still have them. I think I still have 2 cheap plastic ones from 1976, about 200mm long which have slides that I've waxed so they run slick! They were intended for the edu-market so nothing special but are very functional.The story behind those is that in grade 10 and 11 I had a chem teacher who bemoaned the introduction of calculators, saying that students were losing the ability to self check and recognize when a result was in the ballpark correct magnitude. So he forced all his students to get slide rules. In my other science classes and math I could use my first calculator, a TI SR-50,. I loved that thing, it started my interest in computers even though I could see my chem teachers point. He was an excellent instructor with a real degree in science, not education/teachers college. I may also have a third smaller pocket sized wooden core one my father used in his job (electrical engineer) he gifted me around the same time.

author: thermistor-guy
author_rank: Frequent Contributor
timestamp: October 09, 2019, 01:09:55 am
content: Log and trig tables. There were a few kids in my high school with slide rules, but most of us couldn't afford them. My Dad had one, but in his mind it was for adult use only.Quote from: chickenHeadKnob on October 08, 2019, 11:57:02 pmBecause my EE exams always had time pressure, I used to calculate answers twice: once with a calculator, and once in my head to check that the calculation was reasonable. That would pick up large errors caused by wrong key-presses. I'd estimate the answer, then estimate a correction to the first estimate - sounds involved, but after a while it became routine.I still do that now when I help my kids with their Math homework. So now I pick up their keying mistakes.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: October 09, 2019, 05:28:31 am
content: Here is a slide rule for everyone, right on screen. And to cover the operations a slide rule can't do, an abacus is thrown in.

author: bsfeechannel
author_rank: Super Contributor
timestamp: October 09, 2019, 06:20:38 am
content: 1.It was a Faber-Castell 52/82. Required by the school.2.I can't remember. But we had classes on how to use it.3. I never used a slide rule except for the time in school. I gave it away as soon as the classes ended. Everybody had calculators back then. To me it seemed to be an anachronistic tradition. Most manufacturers had already ceased the production of slide rules and I've never seen them used in any professional environment where I worked.4. Several years ago I was struck by a bout of nostalgia and bought a 1973 Faber-Castell 52/82 off Ebay. It came in almost mint condition with minimal signs of wear. I relearned how to use it and now I occasionally show young players the evolution of mathematical mechanization with it.

author: TimFox
author_rank: Super Contributor
timestamp: October 10, 2019, 01:16:10 pm
content: One important side-effect of slide rules was the concept of "slide-rule accuracy" in a computation. It was important to understand when slide-rule accuracy was sufficient (e.g., calculating a 5% resistor value), and when it was not (e.g., balancing ones checkbook).

author: notadave
author_rank: Contributor
timestamp: October 11, 2019, 09:01:16 am
content: I inherited two kinds, one for EE and one for banking.The slide rule has one big advantage: It shows many results at the same time. I marked the E12-series on two regular rulers and my slide.As a human you can perform discrete math with it.I use the concept whenever I have to find e.g. resistors. The E6 values should be1.4678x apart so you can not have any other factor, but because of rounding you can.101218393315182756471.51.51.51.441.42Some are too high others too low.By adjusting the slide rule to the factor you want you can look for the best match even though they should all be the same.

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: October 11, 2019, 11:56:19 am
content: As I mentioned to edy in reply # 23 I have two plastic school slider rules which are11 inches (279 mm ) long and are marked 'Sterling Slide Rule' and 'made in U.S.A.'These are for give-away with edy having first choice of one. You pay postage from Canada. The all white one appears to be a model 684 5 bridge version which has a cracked end bridge on the left. the other one appears to be a model 689 green slider 5 bridge. No model numbers are embossed in the plastic so can't be sure.https://www.sliderulemuseum.com/Sterling.htm

author: edy
author_rank: Super Contributor
timestamp: October 11, 2019, 12:19:33 pm
content: Quote from: chickenHeadKnob on October 11, 2019, 11:56:19 amThanks, I PM'd you my info, please let me know through there how to arrange the rest, thanks again! By the way I also introduced my kids to the soroban to get their heads working because it also helps you keep track of things mentally and in some cases faster than a calculator. With a soroban and sliderule they will exercise their mental muscles and check their answers far better than blindly relying on a calculator.

author: soldar
author_rank: Super Contributor
timestamp: October 11, 2019, 07:38:10 pm
content: I still have my pocket-size Faber Castell "167/87" with the leather slide-in case. I probably got it around 1968.Just basic multiplication, square, cube, log in front and trig functions in back.https://fabercastell.reglasdecalculo.com/167_87/167_87.htmlhttps://www.sliderulemuseum.com/isrm/hmd/fc%20slide%20rule%20pages/fc%2088%20167-87/fc%2088%20167-87.htmNow that I have a second look, those pictures show slide rules in black and white but mine has the sliding scales in green. Otherwise they are alike. I guess it depended on the model year.

author: cliffyk
author_rank: Frequent Contributor
timestamp: October 11, 2019, 09:28:16 pm
content: Here's mine from when i was in school in the mid-late 60s--until needed it was in in my shirt pocket (with a pocket protector of course):Perfect model # too:

author: Johnboy
author_rank: Regular Contributor
timestamp: October 18, 2019, 10:21:25 pm
content: Thanks to all for replies. Fairly diverse around here as far as the rules used and why, and I'm glad to see that diversity. Mainly general-purpose rules, although it seems the specialty rules tended to stick around longer, and I can grok the reasons for that.Today's acquisition was a USA-made-1965-or-thereabouts Dietzgen Microglide 1734. I swore I was done collecting these things, but an infamous auction site, via email, "helpfully" warned me to the fact that there was one available for actually less than it sold for in 1965, so I found myself being thanked for my order before I could come to my senses and remind myself that I need another slide rule like I need an aperture in my forehead.The Dietzgen Microglide, by the way, was not a huge seller in the States, compared to the bestselling models by K&E, Post, and Pickett. It was one of the better-selling models of Dietzgen's own slide rule products, though, and I saw why as I ran the slide for the first time-- absolute butter. The slide moves almost of its own accord. I was reminded of the first time I played a Paul Reed Smith guitar back in the early 1990's and how low the string action was to the fretboard-- one barely had to touch them to fret them. This slide rule is the same thing-- mechanically efficient to the extreme. Turns out Dietzgen came up with a fairly masterful design concept: "Let's put Teflon inserts on either stator so there's less resistance for the slide." And boy, does it work. Let me tell you it works. Anyone here who's compared a mahogany rule by K&E to a bamboo rule made by Post or Hemmi knows the latter have an almost reptilian smoothness in comparison. Well, these Teflon inserts are so enabling of horizontal, seemingly-frictionless movement that it makes the bamboo rules feel downright clunky. (See the cross-sectional picture below; the teflon inserts are the U-shaped things between slide and stator, and they run the entire length of the latter on both edges of the slide.)So why wasn't everyone using them back then? It works like a dream! Ah, there's the rub, no pun intended.Most slide rules take quite a beating in the mail, and this one was no exception, so the alignment of the upper bout was out by an half-centimeter. I grabbed a screwdriver to put it back in alignment, and wouldn't you know it?Darned near impossible.This thing is so slippery when making tiny adjustments that it's like trying to hold an angry mamba recently kicked by a horse. Try as I might, and wrestle with it as I would, there was nothing I could do to get this thing exactly right. Even gradually tightening the stator screws was like kicking that snake again. The Teflon simply works too well; too much of a good thing.So I'm off to find a second vise to finish the job. Might need to borrow a couple of extra hands while I'm at it, at this rate.

author: bsfeechannel
author_rank: Super Contributor
timestamp: October 19, 2019, 04:59:23 pm
content: Quote from: Johnboy on October 18, 2019, 10:21:25 pmSilicone grease works wonders on my all-plastic Faber-Castell rule.

author: artag
author_rank: Super Contributor
timestamp: October 19, 2019, 05:23:36 pm
content: Quote from: MarkF on October 05, 2019, 06:20:54 pmThere are some beautiful circular Russian slide rules widely and fairly cheaply available on ebay. Strongly recommended for slide-rule fans.https://mostlymaths.net/2013/11/my-russian-kl-1-circular-slide-rule-and.html/

author: Johnboy
author_rank: Regular Contributor
timestamp: October 20, 2019, 05:46:09 am
content: Quote from: bsfeechannel on October 19, 2019, 04:59:23 pmThank you. I have some around for heat sinks and I'll give it a shot. I have read that it's useful, but most of the info I've read about care and maintenance is decades old and I didn't want to damage them. I've gotten into the habit of carrying a slide rule at all times; I find them a great distraction while I'm being "processed". I'm also one of those people who look up from their slide rules and note that everyone around me in the doctor's office is playing with their cell phones. They never seem to notice anything odd, and if they do, they don't say, "pardon me, sir, but you seem to have a rather large grease stain creeping through your breast pocket."

author: edy
author_rank: Super Contributor
timestamp: October 30, 2019, 01:33:54 pm
content: Thanks to @chickenHeadKnob who graciously has allowed me to introduce my household to the slide rule. Now I have a few questions after reading the various manuals on calculating using a basic Sterling slide rule (having A, B, C1, C, D, K, S, T, L rules) and having to actually start using them in practice with my 10 year-old who was doing basic multiplication and division yesterday! By the way we also have a Soroban so I am trying to figure out how the Slide-Rule fits in with my strategy to work the brain muscles of my 3 kids.Firstly, for doing multiplications of two 3-digit numbers, for example 761 x 423, I am using a Soroban to essentially add up the following:3 (1 x 423)20400180 (60 x 423)1200240002100 (700 x 423)14000280000===== SUM321903Of course all this is done in the Soroban "on the fly" so you move beads around as you pair-off multiply the various digits so it is fairly fast but most importantly, it comes up with the exact answer. So I was going over this with my 10 year-old daughter and trying to show her how to use the slide-rule and I was puzzled as to how to get precise exact answers, if there is some "trick" or not. If they were used for calculations that were critical to have exact answers, how was that done?Right now, to do the above multiplication I would set the numbers to scientific notation as 7.61 x 10^2 * 4.23 x 10^2. Then I would slide my "C" rule index 1 (the right side one) to match up with the 7.61 on the D scale, then wander along on the C until I see 4.23 and then read off the D scale. So I tried it out on this virtual slide rule:http://www.antiquark.com/sliderule/sim/n909es/virtual-n909-es.htmlSo I did that as precisely as I could and ended up with 3.21 - 3.22. Of course, keeping in mind the 10^2 * 10^2, the answer ends up being 3.21-3.22 x 10^4 or around 321000 - 322000. This is approximately close to our exact answer of 321903. However, I had to make sure I lined up the "C" index 1 with 7.61... not exactly easy, and any error there would also misalign the 4.23 as well which would throw off reading the answer. And even when I did get an answer it would be only to maybe 3 digit precision, +/- on the last digit:How am I supposed to get exact answers? Is there a way of "dividing and conquering" with this thing? Is it purely a quick estimation device? How could they land people on the moon using non-exact answers, or am I missing the point? More importantly... I am trying to teach my kids how to use and integrate the slide-rule into their homework and the math they are being asked to do wants exact answers!Same goes for division... My daughter is learning simple long-division such as 3157 divided by 7 where we do this:4 5 1________7 | 3 1 5 72 8----3 53 5-------0 77- -----0So with the slide-rule, I would use the "C1" and "D" scales again as follows with 3.157 x 10^3 and 7... First I slide the 3.157 on "C1" to match up with "1" on the "D" scale so I am actually multiplying 1/3.157 with 7 on the "D" scale. I then slide cursor over to 7 on the "D" scale and I can see that my "C1" scale shows just barely over 4.5:Again, keeping tabs on our powers we would have to divide out 10^3 (3.157) by 10^1 (of the 7) so we get 4.5 x 10^2 which is 450 or close to our answer but not exactly.Can someone please let me know how (or if) I should be integrating a slide rule into these types of math problems the kids are getting at this point? If it is not possible to get the exact numbers they need for their test, is it just an easy way for them to check? Is there something else they can use it for? I am excited about using the Soroban and Slide-Rule with the kids and forgetting the calculator but I want to make sure I am using them in the appropriate ways.

author: artag
author_rank: Super Contributor
timestamp: October 30, 2019, 03:21:51 pm
content: I'm no expert and I hope someone will correct me if I'm wrong, but I wouldn't want to use anything liable to cause a grease stain.From experience with other tools, I'd suggest that if the slide rule has wooden slides, beeswax-based furniture polish (as used by woodworkers to protect cast iron surfaces without staining the woodwork job) would be good.If it has plastic slides, I'd use silicone spray (mould release, also used on plastic curtain rails, a silicone oil in an alcohol carrier) or PTFE 'dry' cycle lubricant (which is PTFE flakes in an alcohol carrier).I wouldn't use thermal grease. Although the silicone content would OK, i'd be less happy about the zinc oxide or whatever filler it is that gives it the white colour.

author: rstofer
author_rank: Super Contributor
timestamp: October 30, 2019, 03:34:57 pm
content: You don't get exact answers with a slide rule but you probably don't have exact input either if the numbers come from measurements. That's the whole point of slide rules: Fast and close enough! If you want precision, you drag out pencil and paper and get with it,I wouldn't introduce the slide rule until logarithms come up and that's usually at some time late in high school. Even then, I would introduce it as a novelty. The slide rule was king when I was in college right up until HP introduced the HP35 calculator. That was the death of an era, may it RIP.The HP35 was magnificent for its time but it pales in comparison to the advanced calculators available today. Not only do we have great calculators, we also have computers and software like wxMaxima, MATLAB, Octave, Mathematica and a host of others.Things have changed, the slide rule is an artifact. A glorious one, we mostly got to the moon with slide rules, but nobody wants to go back to using one as an only tool.

author: soldar
author_rank: Super Contributor
timestamp: October 30, 2019, 03:49:30 pm
content: Quote from: edy on October 30, 2019, 01:33:54 pmMy 16 cm pocket slide rule will give me about 3 digits. A bigger one will give you more but forget multiplying two five digit numbers and getting a ten digit answer.You are not dealing with exactly precise numbers. In engineering you rarely need to. One thing I notice about beginners in engineering is that they will carry absurdly precise numbers. A resistor of 56.367 ohms and a transistor with a current gain of 156.78. Those things are meaningless. Just the physical variations among units will make those numbers meaningless.If you need more precision then you need other tools.

author: artag
author_rank: Super Contributor
timestamp: October 30, 2019, 04:28:33 pm
content: When I was at high school, my father was selling early calculators to business users. They were common, but too expensive to be found in high street shops or given away as gimmicks. I made pocket money doing repairs to Canon desktop calculators (nixie tubes, RTL and silver delay-line memories), and Bowmar pocket models that needed Nicads replacing.A few of us science geeks bought our own calculators in the 6th form (I don't know what that is in US grades, but it's the last 2 years of school before going to college for a degree course). My technical drawing course required me to buy a slide rule but I wasn't required to have one for maths (though we were taught to use them).Nobody was expected to buy a fancy expensive calculator and our teachers cautioned us against using excess and inappropriate precision, both because it wasn't needed and because it wouldn't go down well with the exam board. Exams were based around slide rules - so calculations didn't need to be precise, just as in real life. The situation is different now : the exams are set using the assumption of either manual methods or calculators so exact answers are expected purely for convenience in marking. Inexact answers would be because of errors, not approximations (though they might expect proper rounding strategies).Students should understand this, IMO. But should also appreciate that many problems can be adequately solved using 2 or 3 digits of precision, and for non-exam purposes a slide rule or an approximation (like 3 for pi) for calculations in your head is good enough to get you a ballpark answer.I suspect the reason slide rules for good enough to 'go to the moon' is not that they were used to get precise results for long calculations planning a flight in detail. Instead, they would be used for a succession of rapid calculations that effectively iterated to a result : eg calculating the burn rate for the next few seconds and then repeating the calculation seconds or minutes later.

author: bsfeechannel
author_rank: Super Contributor
timestamp: October 31, 2019, 05:02:03 am
content: Quote from: edy on October 30, 2019, 01:33:54 pmThe slide rule is an analog calculator, so precision is, in theory, arbitrary, only limited by the resolution of the scale. However, you will see its use, when compared to the soroban, when you have to calculate things like f = 1/(2π · √(LC)), the resonance frequency of an LC tank.Let's suppose that C = 470pF and L = 3.3µH. First, you figure out the powers of ten: 470p = 470 · 10⁻¹⁰ and 3.3µ = 10⁻⁶.10⁻¹⁰ · 10⁻⁶ = 10⁻¹⁶. Therefore, √( 10⁻¹⁶) = 10⁻⁸.So f = 10⁸/(2π · √(4.7 · 3.3)). Now let's get the slipstick.Find 3.3 on scale A with the help of the cursor line. Now place B 1 under the cursor line. Move the cursor line to 4.7 on scale B. You will find 15 something on scale A. If you don't move the cursor, you'll find its square root on scale D below under the same cursor line to be about 3.95. If I flip the rule, I have the CIF scale, which is the C scale inverted and divided by π. This will give me 1/(π · 3.95). So maintaing the cursor where it is, I align C with D and read something that is a tad grater than .0805, let's say .0806. Dividing by two, it gives me .0403.So, f = 0.0403 · 10⁸ = 4.03 MHz.My vintage Casio fx-21 gave me 4.0412361 MHz. Not bad for abeginner. There must be other ways, who knows, faster and more precise than what I did. But setting the cursor and the slide just two times each, without counting flipping the rule as an operation, you get your result very fast.

author: edy
author_rank: Super Contributor
timestamp: November 01, 2019, 03:40:42 pm
content: Were there Venier scales used on slide rules to allow better precision? For example, like found on calipers as follows:So far I have been eye-balling it and getting close. I'm using a practice app for iPhone called RuleCoach. It's free and tiny, shows you complex problems and tells you how close you are and tallies up your average error. It contains no virtual slide rule... you use a physical slide rule, it just gives you random calculations to do. I find it hard to keep track of order of magnitude... but getting better. Very good for learning!For example if I do a few numbers together I have to keep track of the final value being larger. For example if I multiply 2x2x2=8. Or 20x20x20=8000. Because each is 2x10^1 so answer is x10^3. But if I use a larger number like 3x3x3=27... 30x30x30=27000, on slide rule I get 2.7 but actually need to remember it is 27x10^3. If I use say 5x5x5=125 it is now 10^2 greater just due to the digits never mind the original scientific notation. So that's a bit tricky at first.

author: edy
author_rank: Super Contributor
timestamp: November 01, 2019, 07:42:28 pm
content: Seems like this Vernier question has been brought up before. There is even a Google patent for it from 1947 (https://patents.google.com/patent/US2424713A/en). Check out the patent PDF, it is fascinating:https://patentimages.storage.googleapis.com/d2/ab/ad/c6d43a2420897c/US2424713.pdfBut could be it wasn't practical to implement or worthwhile? Or could be with proper technique you can use the slide rule itself as a Vernier... look at the method described in this article from 1948:"Utilizing the Vernier Principle for Precise Readings of Slide Rule Settings"https://aapt.scitation.org/doi/abs/10.1119/1.1991139?journalCode=ajpHere is the text (it starts below at bottom):

author: bsfeechannel
author_rank: Super Contributor
timestamp: November 01, 2019, 08:07:10 pm
content: Quote from: edy on November 01, 2019, 03:40:42 pmNot sure. However, loupes were used.

author: edy
author_rank: Super Contributor
timestamp: November 08, 2019, 01:24:40 am
content: I noticed a mark on one Sterling slide-rule (graciously provided by @chickenHeadKnob) which first appeared like a pen mark at 785, but then after seeing it on both A and B scales and a 2nd slide-rule, I realised it was actually a gauge mark printed from the factory! The 785 is presumably Pi/4 which is 0.7854. It is visible on the pictures in the Sterling instruction manual but not mentioned explicitly.I am trying to figure out what this can be used for and how you would do calculations with it. Why is Pi/4 so important, but not Pi/2? Or 2 Pi? Or Pi squared? Any ideas?

author: jklasdf
author_rank: Regular Contributor
timestamp: November 08, 2019, 01:45:43 am
content: It's apparently for quickly finding the area of a circle given the diameter:http://www.tbullock.com/sliderule.html

author: cliffyk
author_rank: Frequent Contributor
timestamp: November 08, 2019, 01:52:41 am
content: jklasdf beat me to it...Area of a circle is: r² * pi(), or d² * pi() / 4... A shortcut to getting circular area from diameter, volume of a cylinder from diameter and height, and other geometric formulae involving circular functions...

author: Tom45
author_rank: Frequent Contributor
timestamp: November 08, 2019, 05:37:00 am
content: Now that you know that they are called gauge marks, a search can find many references listing various gauge marks. For example:http://steves-sliderules.info/rule%20code/Gaugepoints.htmlThe K&E slide rules I used back in the day didn't have gauge marks and I was unaware of them until I started collecting slide rules many years later. Gauge marks seem to be much more common on European slide rules. They are also more common on specialty slide rules such as for electrical engineers. In the link above you will see gauge marks for copper and for converting between horsepower (HP) or Pferdestärke (PS) and kilowatts.The K&E Decilon that I got when it was introduced while I was in college had only one gauge mark: pi on the C and D scales. A later variant of the Decilon dropped those pi gauge marks. With the folded scales (CF, DF, CIF) pi was always available by going between the regular scales and folded scales at the appropriate step.

author: Canis Dirus Leidy
author_rank: Regular Contributor
timestamp: November 08, 2019, 05:27:41 pm
content: A some useless numbers. The approximate amount of time required to complete (include the writing on paper) these operations using an ordinary slide rule.Multiplication of any two numbers: 10 seconds.Division of any two numbers: 8-10 seconds.Squaring and cubing: 3-4 seconds.Calculating of square and cubic roots: 4-5 seconds.Calculating trigonometric functions: 4-5 seconds.Calculating complex formulas (like (π^(1/2)*cos^2 x)/(x^(1/3)) ): 30-50 seconds.Source:«Кущенко В.С. Логарифмическая линейка. — 1958»

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 09, 2019, 02:32:56 am
content: Those times seem slow to me, maybe by a factor of two. Based on my memories of slipstick days. Of course the time depends on the specific numbers and where the rule was left after the previous calculation. It certainly was that slow, or maybe a bit slower sometimes.Just

author: Canis Dirus Leidy
author_rank: Regular Contributor
timestamp: November 09, 2019, 07:45:38 am
content: Quote from: CatalinaWOW on November 09, 2019, 02:32:56 amThe author also included the time needed to (hand)write the result on paper.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 09, 2019, 04:20:06 pm
content: So I guess the question is. "Is it faster to write the answers down on paper when using a calculator or a slide rule?"Or not, it is a silly question. The data can't be used to compare the two since intermediate answers are only written down occasionally with either tool. Probably more often with the slide rule because of the need for additions/subtractions.

author: Johnboy
author_rank: Regular Contributor
timestamp: November 10, 2019, 11:07:58 pm
content: There were "slipstick contests" where the "fastest guns in the West" faced off with their slide rules to compute various equations. It was even a team sport at some colleges, apparently. I have yet to see any actual photographs of a slide rule team.It seems that many of the techniques that were used to rapidly arrive at an "answer" have been largely forgotten. One of my favorite slide rule tricks I discovered playing around with them was one I later discovered was also used by the celebrated physicist Richard Feynman at Caltech during his lectures.Feynman (as many of you probably know) was quite skilled at mental math without need of a pencil or calculator for many of the problems he demonstrated on the board. He could occasionally produce a correct answer, using his simplex Pickett rule, to include four or five figure answers. For multiplication of two given numbers, for example, he would mentally multiply the last digit of each number together, then pretend to find this final digit on the rule itself. He never admitted using the technique, exactly, but it's largely believed by the faculty that that's how he was doing it. Probably "old hat" to some of you who actuallyhadto use a slide rule in school.Anyway, speaking of techniques, I never bothered to learn how to use the CI scale at all until I read an English translation of one of the Japanese Hemmi manuals and it was quite a revelation. There are a lot of different ways to skin a cat using a slide rule, I guess is what I mean by this rambling post.

author: Nusa
author_rank: Super Contributor
timestamp: November 11, 2019, 12:30:31 am
content: Quote from: IanB on October 05, 2019, 05:31:04 pmTrue, right around 1974 if I remember right. However, they took a few years longer to wipe out teaching with trig and log tables, since the mass market calculators didn't have scientific functions. And the scientific ones were still too expensive for most (cheapest about $150 in 1974).I had one of those cheap round ones I used in 1972-3 High School Chemistry class. That was the last time I used it, too. I also have a couple of my Dad's slide rules now. One is marked ACU-MATH No. 500 and seems pretty basic. The other is marked Picket and Eckel, Chicago 3, USA, Copyright 1948 Model No. 500 Ortho-phase log log with scales I do not know the function of.

author: cliffyk
author_rank: Frequent Contributor
timestamp: November 11, 2019, 07:32:13 pm
content: My first handheld calculator (ca. 1973 or so IIRC) was a Sperry/ Remington 661-0; a "full function" (+,-,*,➗) 6-digit, blue fluorescent display. No memory, but you had your choice of 2 or no decimal places; it was a marvel at the time:Times have changed...