Concise Fun

Today I visited the bank.

Normal every day kind of thing. But…

I was in a hurry and had in my hand an object that I sat on the counter as I signed things. I’d not got it put back in its sleeve. It was a small thing, about 3 inches in diameter (84 mm or 3 5/16 inches). I’d not thought a lot about it. I only had it with me as I’d been working a couple of minor problems (the error bands on cubits) and occasionally needed a bit of help on some of the numbers (like what IS 365/366 x 6.02 compared to 6?)

The clerk, toward the end of the transactions, asked me: What’s that?

He looked and pointed.

I looked.

I felt old.

It suddenly dawned on me that not only where these things uncommon and maybe even out of fashion, they were now unknown, even to this young man who dealt with numbers all day long and was at least a “20 something”.

It was my “Concise” Circular Slide Rule number N-28:

Concise Circular Slide Rule N-28 front

Concise Circular Slide Rule N-28 front

Available from these folks (who still make them, thank God…) for 1000 yen (about $12 at present Yen rates).

I let it soak in for a moment that I’d done the moral equivalent of showing up in Spats and with a vacuum tube radio… with my horse parked outside…

Then I explained with as much positive manner as I could muster that it was an antique computing device called a “slide rule” and that in ancient times, like when I was in high school, all Engineers, Chemists, Physicists and in fact anyone in Science learned to use them. That we did all our problems on them as there were no calculators “back then”.

He looked fairly interested, so I looked over my shoulder and saw there was no one waiting… And pressed on: “Here is how to multiply 2 x 2. Set this starting mark next to 2, now read off the result next to the other 2.” He said “And it even has Pi on it!” and I said “Yes, see, if we set the index at Pi, all the Pi x anything answers are all displayed at the same time, we just have to pick the one we want. Also, you could want a circle of, oh, 6 inches, and just find 6, then look under it for the diameter…. and it doesnt’ need any batteries and it always works. Fits in my shirt pocket too…”

Then I paused. Expecting the slightly forced smile of someone “tolerating” an elder… Accepting that some folks will always want their movies to be in Black and White but they look harmless enough… What I got was an enthusiastic: “Wow, that’s cool!”

Rarely have I felt so happy in explaining something and never have I been so happy in a bank…

This kid “got it” (“kid”, probably 22?) in about 20 seconds. No chargers, no batteries, plastic and waterproof, works in a hurricane or an earthquake power outage. Lets you SEE the problem not just a row of numbers on a display… I told him what search terms to use in Google to find one if he wanted one (redeeming my place in modern society ;-) and left the bank.

My “Collection”

Yes, one of these lives in my “emergency restart the world kit”. One often visits my pocket too. I’ve also got a 6 inch “pocket Pickett” along with the model (NEW in box) that went to The Moon on Apollo as their “backup” to the computers. There are a couple of very large plastic ones that were my ‘day to day’ users and there are the two metal Picketts that were my college and work rules.

I don’t use them as often as I ought. Age means I now have to hunt up my glasses to get more than 2 decimal places of accuracy out of them. But sometimes I take them out. Sometimes I find them on the shelf asking to be “taken for a spin”. Every so often I run some numbers and see if I still remember Avogadro’s Number and can set up a 4 or 5 term equation that then just ‘reads off’ without moving the slide (the art of using multiple markings at once, using the inverted “C” scale creatively…) Or the square and cube scales ( “A” and “K”). Old friends, taken out for a beer at the local pub as we talk about “the old days” when we worked together every day, before they went into that retirement home…

So now I’ve decided to not hide this one when I’m using it. To maybe leave it laying on the counter after figuring tax and tip. To clearly hold it in view while figuring wood needed at the lumber yard. To take my friend to the park, and to the shop, on the way to the pub… And maybe even have him help out on that project I’m building in the back yard… A little Henge time might be good for the ol’ guy. Remind him that there are folks even older than him that still can get in a good days work ;-)

For anyone interested in playing with a slide rule, but not having one at the moment, there is a very interesting curiosity. Folks have made GIFs of the parts and put them in image frames so you can slide them back and forth.

That, of course, is all you need to make a working, real, slide rule. Never mind that the compute power being consumed to do this is orders of magnitude more. Just savor the moment of getting on that DisneyLand Animatronic Horse and taking a little gallop around the track:

A Pickett N-909 – ES (the yellow one). This was my main rule all through college. I still own one of these:

The N-600 S (that small “pocket model” that I have, though mine is white):

And yes, both of those are “working” slide rules that you can manipulate with your mouse.

This guy is even more “into it” than I am, and his site has several (many?) pictures and descriptions:

There is even an International Slide Rule group (though I’m not a member):

And with that, I think I need to acquaint my ‘kids’ with my slide rules so they know not to just pitch them out some day when they inherit them. After all, they are “cool” now ;-)

The front and back of the one that lives in my Doomsday Kit. The Engineering model (2600 yen, 4 5/16 inch so more precise):

Model 300 Front

Model 300 Front

Model 300 Back

Model 300 Back

The small one that lives in my pocket has a handy set of formulas on the back, but not any working marks:

Model 28-N Back

Model 28-N Back

But unlike the larger one, it does fit fairly easily in a normal shirt pocket.

This link takes you to an “index” page of many other simulations:

Including this one that has numerical readouts for the various scales(!):

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About E.M.Smith

A technical managerial sort interested in things from Stonehenge to computer science. My present "hot buttons' are the mythology of Climate Change and ancient metrology; but things change...
This entry was posted in Human Interest, Metrology, Science Bits and tagged , , . Bookmark the permalink.

29 Responses to Concise Fun

  1. H.R. says:

    Memories… I did all my high school science and math with a slide rule. I didn’t start college until ten years after H.S. By that time, calculators were readily affordable and slide rules were in the dustbin.

    The college freshmen entering with me had never used slide rules. In one math class, the Prof spent a half hour teaching the class how to use a slide rule just to make a point that you have to understand the relationships between numbers and functions and calculators just don’t do that. You push a button and there it is.

    The young’uns by and large didn’t “get it” and were glad to go back to calculators the next class.

  2. dearieme says:

    We used the conventional sort at school. When the teacher was out of the room you could use them for a sword fight.

  3. Joe says:

    There is a funny bit in Dr. Strangelove where he uses the circular slide rule to calculate how long survivors will have to stay in the cave …. calculating … 100 years!

  4. Larry Geiger says:

    Dude, you are so bad. We need to get you one of those T-shirts that say “Old guys rule” or something like that.

  5. Adrian Vance says:

    What a trip back in time. I used to teach kids to use these things and they were a great boon to the physical sciences. The great drawback was that you were seen as a “nerd” if you carried one and that meant the hot girls would not be seen with you. But, we got on with the smart girls who needed help in the lab. Somehow, it all worked out….

    Conservative thought, science and humor at The Two Minute Conservative, for radio/TV hosts, opinion page editors and you. Also on Kindle.

  6. H.R says:

    @Larry Geiger.

    Funny you should mention that. I was sent the following joke yesterday. I discourage forwarded junk and generally treat it as spam (sorry, mom; sorry brother), but this was a good one and fits right in with your comment.

    “One day an old German shepherd starts chasing rabbits and before long, discovers that he’s lost. Wandering about, he notices a panther heading rapidly in his direction with the intention of having lunch.

    The old German Shepherd thinks, “Oh, oh! I’m in deep doo-doo now!”

    Noticing some bones on the ground close by, he immediately settles down to chew on the bones with his back to the approaching cat. Just as the panther is about to leap, the old German Shepherd exclaims loudly,

    “Boy, that was one delicious panther! I wonder, if there are any more around here?”

    Hearing this, the young panther halts his attack in mid-strike, a look of terror comes over him and he slinks away into the trees.

    “Whew!,” says the panther, “That was close! That old German Shepherd nearly had me!”

    Meanwhile, a squirrel who had been watching the whole scene from a nearby tree, figures he can put this knowledge to good use and trade it for protection from the panther. So, off he goes.

    The squirrel soon catches up with the panther, spills the beans and strikes a deal for himself with the panther.

    The young panther is furious at being made a fool of and says, “Here, squirrel, hop on my back and see what’s going to happen to that conniving canine!”

    Now, the old German Shepherd sees the panther coming with the squirrel on his back and thinks, “What am I going to do now?,” but instead of running, the dog sits down with his back to his attackers, pretending he hasn’t seen them yet, and just when they get close enough to hear, the old German Shepherd says…

    “Where’s that squirrel? I sent him off an hour ago to bring me another panther!”

    Moral of this story…

    Don’t mess with the old dogs… Age and skill will always overcome youth and treachery!
    BS and brilliance only come with age and experience.”

  7. Funny…I also have several slide rules, made out of bamboo!
    Those were the days my friend….
    Now, everything is Post Normal! :-)

  8. PaulID says:

    I would love to learn to use a slide rule are there any beginner tutorials online that you know of or would recommend?

  9. Phil says:

    I had one made by Sama & Etani that I owe both my high school and college degrees to: The inserts were more valuable than the slide rule as I got one of the early HP scientific calculators, but the inserts were not replaceable, nor have I ever found anything since that has so much scientific and math info in such a concise format. I am trying to interest my kids in them, but they are still a bit too young.

  10. pyromancer76 says:

    People might like to think of you as an” old dog”, but I think you are just full into your maturity. More power to you as you think these issues through, inform others of them, find that they are unusual (not too many people can think like you in such fine detail), highly attractive, and, most importantly, liberating. The free market possibilities of the internet are quite amazing.

  11. John F. Hultquist says:

    I have a Model N 4 ES Dual Base Log Log
    I saved the box and instruction booklet. The booklet claims a price of 50 cents and a date of 1959. Same date on the “eye-saver yellow” rule. They came in white, also.

    I think I probably bought it in early 1961 but do not remember the price. It has a leather case with a D-ring and ~4 inch strap to attach to your belt. Those so dressed were the geeks. About 1965, carrying a big box of IBM punch cards was the thing, maybe a large spool of magnetic tape, too. Then the TI calculators took over.

  12. j ferguson says:

    E.M. and all,

    In a recent discussion at another site, one of the engineers was maintaining strongly that he was a Nerd, not a Geek, I suggested that to be a Nerd, he would have to be familiar with the Log Log Duplex Deci-Trig, or the Pickett, or Post equivalent. He had no idea and so will forever be a Geek, if that.

    At some point in the not too distant future there will be a display box with mine, my father’s, my father-in-law’s, and my brother-in-law’s, along with the HP-35s, The TI-59′s, and my Pickett large circular with the two cursors on a clutch. Regrettably, I can’t furnish a photo because I’m on a boat and it’s in storage. Maybe it should be the other way around.

    And I can probably add a prayer wheel from my flying days.

    I did enjoy the sense of accomplishment at listening to a Frieden or Monroematic clatter out answers.

  13. j ferguson says:

    Sorry John Hultquist. I didn’t read your note carefully vis a vis Geeks, No offense intended.

    But in the Midwest Geeks were still working the chicken circuit in 61. In Saint Louis, you were a Nerd, but then memories can be confused in advancing age, or at least mine.

    The pocket protector with the Hollarith cards behind it was even more impressive if the punch-outs were round rather than rectangular as they were, with Remingtons – or was it Sperrys? Univac in any case.

    Wash U had a 650 in 60 and then a 360 later on. I don’t have any idea where the supply of round hole cards came from, possibly one of the local hospitals.

  14. j ferguson says:

    The Curta Coffee Grinder, surely someone here had one.

  15. John F. Hultquist says:

    j ferguson
    Sorry John Hultquist. . . .

    No problem. I just went to the net to find out the meanings. It seems they change. My concept has been that geek had to do with having technical skill and nerd with not having social skills. I mostly agree with the thought that I probably would not want to belong to any group that would have me.

  16. Sera says:

    Yep- bamboo slide rule in a little red box. I also like to have a ‘Pocket Ref’ on the workbench. Everyone should get one, there is even an online version.

    Ordered the Lee ‘hardware’ and loving every minute of it. Thanks again.

  17. E.M.Smith says:


    The next to last link in the article has some “how to” guides in it. Pretty simple, really, put the starting “1″ under one number, look up the other number on the other line of numbers, answer is back on the first line of numbers (for most simple uses). The sliding cursor with a hair in it is used for precise guessing about just exactly how aligned two lines are.

    The basic process is that you are adding logarithms. So two linear sticks add things if put end to end. Mark log scales on them, and you are adding logs. Adding logs gives you the multiplication result. Subtracting them (going the other way) gives you the division. Use a scale that is twice as short (i.e. the A scale) and you get a square or square root (depending on which way you read it). The “K” scale gives cubes and cube roots…

    The “Ci” scales is just a “C” scale run backwards (that makes some kinds of division a bit easier to ‘set up’ so you can multiply one way on the “C” and “D” scales then immediately read off a ‘divide by something else” on the “Ci” scale.

    After that, it starts getting complicated ;-)

    The link referenced includes this pointer to a site that shows you how to use one for each of several kinds of problem by showing you the rule ‘as set up’. Or “by example”.

    FWIW, after a while you start to visualize the set up (tracking the x10 factor in your head) and sometimes realize you know the answer without actually moving the slide rule… Very freaky the first time it happens to you, kinda cool after that… sad when you realize it’s gone away and you need to do some more actual use to get it back…

    But as a first example, click on the link for the N-909 sliderule above. Put your cursor on the “slide” in the middle of the slide rule (the long yellow part, not the clear plastic thing with the red line in it…) and ‘slide the slide’ until the “1″ at the bigging (left) of the slide “B” scale is exactly under the “2″ on the frame “A” scale. Now look to the right on the B scale until you see a two. What’s the number on the A scale above it? That’s an example of 2 x 2 = 4. Now look at the “3″ on the B scale. What’s above it? Yup, 6. You have every 2 x (whatever) answer already there. You can now slide the clear plastic thing with the red line (also called a ‘cursor’) over to any desired answer.

    Put the red line on the 3/6 pair. Look down on the bottom side of the frame at the D scale. That’s the square root of the A scale (or the A scale is the square of the D scale). Notice that 4 on the A scale is over 2 on the D scale. Under your red cursor line is the square root of 6. Look to the left a bit, see the numeral 2? That’s the most significant digit. Now count ‘big ticks” There are 4 of them (notice that the number of ticks to a full count change as the scale compresses, in this case, it’s 1:1, so that a count of 4) that gives us 2.4x Now notice that you are between the 4 and the 5 ‘big tick’ count. In this case, each ‘little tick’ counts for 2, so we’ve got 2 of them, plus a bit under 1/2 of one. I’d make that about 4.8 (but at that point, we’ve got some precision issues) for a total of 2.448 and since a ‘normal’ slide rule is good for about 3 digits of precision, you would round that to 2.45 “for all practical purposes”.

    Excell reports the sqrt of 6 as being 2.449489743 which would round to 2.45 as well.

    So, there you go, one “lead me by the hand” walk through, a mini-theory intro, and a page of examples.

    Easy, eh?


    After I found out about bamboo slide rules, I wanted one, but by then they were no longer available in stores… When they were available, I couldn’t buy one due to no cash and my being unaware, when I became aware, they were unavailable, and now that I’m both aware and the collectors make them available, we’re back to high prices.

    (thus my $12 plastic ‘daily driver’…)

    Ah, well. Someday… (right after I get my contacts updated so I don’t have to search for glasses to actually use it ;-)

    @J Furguson:

    I always wanted one of the “coffee grinders”. A guy in Chem class had one. He had rich parents and was from Germany I think… he got 4 or 5 decimals of precision. I got A’s… ;-)

    a dish best served cold…


    For anyone not aware of it, the bamboo slide rules had a great reputation. Metals ones could stick and needed some lube, and would loosen over time. They also have a high thermal expansion coefficient (that never bothered me, but some folks with hotter hands claimed it mattered..) The Bamboo ones are very slick, and were often precision made in Japan with exacting tolerances. Low thermal expansion and great esthetics. (Nobody ever talks about the esthetics of their electronic calculator…)

    So we of the Metal Rules crowd would look down our noses at the guys who could “only afford” a cheap plastic slide rule (who generally didn’t care, they just bought the damn thing to get the class out of the way so they could go back to biology or whatever…) and then we would ask the bamboo folks if they had sweaty palms problems (humitity absorption was a theoretical issue for wood…)

    Strange. Lots of folks kept and cherished their slide rules. I’ve got an HP-35 that I bought for $400 when new and and HP-45 both in storage somewhere. Don’t really care much. Last time I looked, their batteries has spilled their guts and corrosion had done the deed. “Oh Well” is about how I feel. But if my metal slide rule got bent or the paint scraped off… I’d cry myself to sleep…

    And yes, I’ve still got the leather holster that graced my hip for years and marked me as a True Geek / Nerd … Even have the leather ‘holsterette’ for the 6 inch. Not intended for the belt, but intended to keep it safe in your suit coat for those times you were “Dressed up” or if you got promoted into management (but still wanted to demonstrate your “tech chops” in an engineers meeting…)

    Maybe I’ll ask to have it burried with me as “grave goods” for some far future archaeologist to discover as civilization restarts next time around the wheel…

    Boots on, six shooter on the right, slide rule on the left hip, whiskey flask in the breast pocket… Look on the archaeologists face? Priceless… ;-)

  18. j ferguson says:

    I was puzzled that the K&E which I think was mahogany would warp slightly, and could be sticky, while supposedly being the best slide rule on the market. The Post bamboo rules didn’t have this problem, or any other if it was possible to have any other problem. My God, how could anything be so simple that it could only have one problem – sticky slide? How times have changed.

    I don’t think I own a single thing today which can have only one problem.

    While we’re at it some of you may remember your experiences with ruling pens.

    John Hultquist, I think your geek-nerd definitions are accurate, but may post-date their earlier applications. I can well remember being informed as to the real meaning of some of the words that I’d thrown around as a kid.

  19. Jason Calley says:


    I was a poor student; the meaning being that I had no money. Consequently, my weapon was a cheap, white plastic slide rule in a plastic sleeve. It worked fine, and yes, I still have it, and yes, I could still walk to where it is and put my hand on it, even if it were midnight and the lights were out.

  20. PaulID says:

    Thank you very much for that info I have searched and found a couple basic tutorials and am talking to some of my physicist friends (I like living close to a nuclear research facility I.N.E.L.).

  21. j ferguson says:

    Addition to my burial suit would be the Craftsman 1/2 inch drive 3/4 inch 12 pt socket which with the speeder are the only survivors of the Sears socket wrench set I bought for $9.95 in 1958 with my first $10 earned as an employee of the local hardware store. I guess I must not have encountered many 3/4 inch heads on nuts or bolts.

    Maybe also the Rapidograph which appeared in 1963 and saved us all from our lack of skill at sharpening ruling pens.

    Also, a copy of the two volume set of Chicago Yellow Pages from say 1966.

    Maybe the use of the local Yellow Pages to quickly determine whether a municipality could support technical life would be worth an entire thread. Was there life after Chicago? Damned hard in Miami, or Washington DC – especially Washington.

    Another contribution might be to relate as my memory permits, the observations of a visiting Russian professor to Wash U in 1965 who gave an entire lecture on this wonderful thing which we had and they didn’t. Briefly, he riffled the pages, stopped at some point, speculated on what we would have to do to purchase the item implied by the listing and then described what a Russian would need to do even assuming the thing was available there. I’m convinced that we owe prevailing in the cold war to the Yellow Pages. I wonder if anyone else has thought of it?

  22. Borepatch says:

    Let’s see: two times three is five point nine nine … aw, just call it six.

  23. OldOne says:

    Thanks for the memories too!
    I knew I had one of those too, so I opened my desk drawer & voila, the Concise No.260 circular slide rule.
    Also had a circular s/r mounted on a rectangular plastic case that had slide out plastic conversion tables. Couldn’t find that one.
    Also couldn’t find the old yellow Pickett w/nice leather case.
    Used em thru engineering school.
    Those were the days, pre-electronic calcs.

  24. mddwave says:

    I was in high school during the “last days” of slide rulers. I learned the mechanics of using the slide rule, but never understood the principles.

    As time passed and calculators, computers came, I was doing log-log regressions and I had an “eureka” experience and finally understood the principles used in slide rules.

    I reflect once and a while on how clever and practical engineers/scientists were in the past.

  25. RACookPE1978 says:

    Competed in high school slide rule, number sense (mental mathematics) and science competitions in Texas in 1970-1974.

    Did fairly well in the novice divisions (first and second places regularly in these weekend events across TX) but was too slow for the veterns division as a junior nd senior. Changed to the longer three-hour science tests instead – found that concentrating on the calculation problems for that long was easier than the “sprints” of the shorter tests.

    I still got a few of the slide rule tests as a pdf if anybody wants to try their skill.

  26. j ferguson says:

    Old Readers’ Digest citation:

    “…..calculated with a sly drool.”

  27. Sera says:

    Saw this today, and thought of you and the boys…

  28. E.M.Smith says:


    Cute, very cute ;-) I especially like the guy that looks like he is listening to his slide rule… I’ve done that…

    @J Ferguson:

    Snicker ;-)

    Yes, we had “emergent behaviour” of capitalism and they had centrally planned paranoia. We had folks who would deliver what you wanted over night; they had folks who would interrogate you for asking if the thing was available…


    I think I’ll pass on the ‘tests’… Just reading the things is a challenge these days. (Wonder if there’s a market for “Large Type Slide Rules”? ;-)


    In my High School, we were required to learn log arithmetic first, then learned the slide rule in chemistry class… made it really easy for the teacher to just say “All you are doing to multiply is adding these to logs together using the stick…”


    I still find that sometimes I’ll “do the math” in my head in the format of slide rule mode. Digit point 2 digits and exponent carried in the mind… And the training to ‘set up the problem first’ saves me a lot of time in many places.


    I’ve done it ;-)

  29. tckev says:

    Many other types of rules are at

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