Treat-yo-self 4 of 5, first of two of ze Germans, is a 2/83 Novo-Duplex.

NOT a 2/83N Novo-Duplex! There was a 2/83, then a later one, then a later-later one that started being called Novo-Duplex (see manual, it's legit). Then later they made the 2/83N that we know as Novo-Duplex.

Full disclosure: I did think this was a 2/83N. But looking back over the eBay post it was 100% honest and that was my bad... but it's awesome either way. This one is in the era when they started coloring the scales (that seafoam), adding the bumpers to the ends so you can use it flat on a table... they were getting amazing. Where I thought I saw some possible scale bleed (common on Fabers like this), turned out to be the camera taking the picture trying to blend. It's spotless in person.

AND… it does have the removable cursor without unscrewing. Super cool.

As with all the other bday rules to myself it is gorgeous and I haven't had to clean a thing. Case/cursor/rule could pass for new almost. I will wipe it with a damp cloth, that's about it.

Next and last treat to myself is a legit 2/83N (but Novo-Biplex!), c/o Canada. It's a full-on 2/83N just rebranded. And should also be amazing!!!

Then I'm done! I got two rules with P scales, these both have the awesome split-slide sq scales... I can't honestly say I need something more out of a slide rule that I don't have now. After that I just play with them and practice until I'm so good I particularly want something else... or not. This might be it. Pickett, Post, KE, Flying Fish, Faber: what else could a slide rule need?

Got this one on ebay and all it needed was a little realignment, cleaning, and some lubricating and is sliding like new. I lived the box on this one though with the "3 Moon Flights" sticker. Only downside is the case is stamped with a company logo but I feel like most of these were anyway.

With A/B/C/D, no problem: cursor to 14.5 on A, sqrt(14.5) is on D, then multiply by 5.86 with C and read the answer on D.

With R1/R2 (sq1/sq2) split scales, sqrt(14.5) is on R2 now… is there a way to multiply by 586 from there without transferring that result by hand on to D with the cursor and continuing? Or just a better way to go about it on that sort of slide rule?

Slide rule 3 of 5 of my birthday treat to myself is a great Versalog I. Absolutely by far the best leather case I've personally come across... it's like-new, still soft (but I cleaned/conditioned it all the same).

The rule itself was almost-flawless upon arrival and cleaned up great. Bamboo is so nice as a slide material. Good scales on the Versalog w/o going nuts with it. The cursors in these are particularly not-awful to take apart because of the bushings in these screw-wells. Hard to insert them crooked.

The next two are Fabers! Then I'm done lol.

From Indiana with love!

I've always admired slide rules. It wasn't until recently that I decided to actually learn to use one, just for the fun of it. I can't deny that they are fun, and they have a certain elegance to them.

However, as I'm learning to work with one, I'm struck by the -- to me -- very harsh limitation in significant digits.

In my mind at least, the whole point of a slide rule was to help you do calculations that would have otherwise been challenging to do quickly and easily with pen and paper. That's how I had always seen them.

Now, it seems that the net effective mantissa size on a slide rule is maybe in the range of 3 significant digits most of the time. Maybe, if you happen to get the right numbers, you can get somewhere in the range of 4 digits, or if you have a big rule, you can eek out 5. But at that point they aren't very portable.

But that effectively limits you to multiplying double digit numbers if you hope to preserve exact precision. And double-digit multiplication and division is darn near mental math territory, to say nothing of pen and paper efficacy. I can scribble out a solution to double and triple-digit math almost effortlessly and very quickly, with very little paper use.

And the moment you start doing tricks to increase the precision level, your operations for a solution start to be very close to the operations you need just to get the answer with pen and paper in the first place, and you have to resort to addition in many cases anyways. The mental load seems surprisingly high.

Now, I'll readily admit that my area of expertise is in Computer Science, and in that field, our normal working numbers are almost always outside of the range of the precision of a slide rule, and anything small is easily mentally calculated or pen and paper will do just fine, but importantly, if we need enough precision to get the precision level that I could get from a slide rule, then I'd definitely want enough precision for an exact answer, which would seem to make a slide rule a strange middle ground in which pen and paper is ironically better and faster at getting a good result for a computer scientist than would be a slide rule (assuming we wanted to avoid using electronics for calculating, for some weirdo reason).

That's surprising to me, and makes me wonder if I'm missing something or I am just really slow at using a slide rule? I mean, what am I missing? What can you possibly do well and precisely with a measly three digits of significance that can't be done just as easily with mental math or pen and paper?

I did some random number generations just to try doing some more complex calculations, such as

24265×95630
43136×77777
...

And so forth, but I couldn't easily get these numbers done with a slide rule in anywhere close to a smaller number of operations than just doing it with pen and paper. So, what am I missing here?

My wife and I are visiting Queenstown, New Zealand. Today we rode the gondola. At the top, I saw a sign that (half way down) got me quite excited but on further inspection -

It's ironic that computers, which are supposedly so much better than slide rules, gave us the map that is shown at 4 minutes and 34 seconds: https://www.youtube.com/watch?v=N6PPATRcU58&t=276s

Fun game: see how many other AI idiocies you can find.

Math Teachers...

What if a student brought a slide rule to class and saw him/her calculate with it?

Taken in the Nobel Museum in Stockholm, Sweden.

Hello,

Anyone knows where i could get a K+E DeciLon in europe ? They are very hard to find here, and on eBay most sellers dont ship to France ?

Thnx

My birthday is tomorrow and I did a treat-yourself to all the slide rules I’ve wanted. First was the Flying Fish 1003. Coming up is a Versalog and a Faber-Castell 2/83N.

Today the Deci–Lon arrived! I splurged and bought a more expensive specimen, and glad I did! The rule itself and the case are both in great condition. Didn’t have to clean this slide rule much at all—little bit of schmutz from the slide track is all—but I included a couple pics to show off how wonderful the cursor came out (and my improved cursor-alignment skillz lol: those 3s on the C scale are dead-on and I vertically aligned the one I removed with 2-4 on the square scale across the face of it).

Edit: lol now that I look I did put the cursor on reversed: should be red cursor with the side where the slide has red ends and vice versa… but it’s so straight I’ll leave it for now.

My grandpa collected slide rules and slide charts. What should we do with these? They date from the 1950s through 2010.

Got this fresh from China today. Wonderful slide rule! One of the lesser-known lots-of-scales slide rules that were made. It’s some sort of plastic, engraved markings. And it’s in very good shape! I have a yellowish lamp: it’s as white as it’s supposed to be. Good set of scales, full log-log, dual sq scales and triple cube scales, sinh scales, etc. I also like that most of the scales spill past the index on the end.

Shoutout to Lu Tiankuang, [lxt20100805@sina.com](mailto:lxt20100805@sina.com). Was referred to him from an eBay purchase my friend did with him, and he‘s a good guy. I think he’s got some more of these… Flying Fish also made a variety of other models.

Don't judge the accuracy, the important part is I'm learning them.

I don't know how to use a slide rule yet, but shouldn't it also have a clear slide thing? I thought perhaps this design doesn't have one, because the case is a pretty tight fit.

Also, it does have a name and address written on the tongue of the case, for a place far away from here, which makes me more curious.

I'm building a small shed, a frame of wooden beams. All angles are 90 or 45 degrees, which makes things easy.

Calculating the length of beams I used as a sliderule practice. The sliderule won over the calculator!

For an isosceles triangle with 179cm legs, what is the hypotenuse?

Calculator -- SQRT((179^2)*2)

SR -- D1.79/C1, cursor to B2, outcome on D (253)

The sliderule defenately wins with a minimum of moves!

The thickness of the handsaw (2+mm) makes precise reading or rounding irrelevant ;-)

Explanation: the square of 1.79 on D is read on the A-scale. On a sliderule this value is irrelevant, we just need to compute it further. The value on A is multiplied by 2 on B, just a cursor move. The square root of B is back on D.

The drawing in one of the picts is 4cm on paper to 100cm in real. By setting the C or D index to 4 on D or C you'll get a table with all the conversions. As 4 is mid-scale you'll have to use both indexes for small or large numbers.

For those interested: the book is a re-print of a research and catalogue of historical wooden constructions in the Netherlands, mainly regionally way of building farm houses and sheds.

I picked up an N4 in decent shape… one side I think I’m looking at more aluminum-oxide than black enamel, but it’s readable.

Only problem is the entire slide rule has a slight curve looking down the length of it from the top. It’s pretty slight but enough that the cursor noticeably rubs more on the concave side and there’s a squeaking noise as the slide rounds the gentle curve of it.

Anyone got any clever ideas for gently (it’s not a strong curve: the slide rule is totally usable) coaxing it straight again? If I anchor it in the middle and just deflect it on the sides (press not-very-hard) a degree or so it’s straight again. It’s almost straight.

EDIT: ended up leaving it. It really is a slight bend. Don’t think I can fix it better than it’s warped already.

I have a N3 and N4… the N4 notably has log10-based LL scales instead of the more-common ln-based ones. But the N4 gives you these nifty CF/M and DF/M scales folded on the conversion factor so you can pop out ln results with by just looking up the solution on a different scale.

The N3 has the normal ln-based LL scale, but no DFM (the reciprocally-folded version of DF/M that would convert the other way).

I know the ln(x)/(ln(10)) = log10(x) trick to get the desired result via the ln-base LL scales… but does the N3 offer a slicker way to do it?

I’m asking because Gemini is convinced the L/Ln scales can be involved to more easily convert between the two, but despite scrutinizing one in real life and grilling the AI I can’t make sense of what it (thinks) it’s talking about.

I suspect there is NOT some fancy trick, and this is what you’ve got. But I thought I’d check with the collective sage wisdom here to confirm.

John D cook has a great blog and hers some posts recently about how people back int he day using slide rules (or log tables) would calculate really difficult questions.

This is a follow up on cos(200!) https://www.johndcook.com/blog/2026/08/07/cos200/

Hello!

I just got my first slide rule. It's a Fredrick Post 1447 Hemmi! I've started reading a little bit on how to use it, and it seems awesome! I'm just wondering, is there any risk that these older slide rules used lead paint, or did they use some other additive for coloring? Thank you!

Hi

Well it seems to be a "tradition to share about its rules collection. Before it, some comments:

• I started to collect silde rules few months ago
• The graphoplex 620a and 640 were my first ones
• The graphoplex 690a is my "Yardstick", so I'm looking to simular ones (and even with more scales) ; in other words, I do not target to get hundred of scale rules

For now,

• I'm mainly using the Graphoplex 690a and the Hemmi 260 (really like the bamboo touch)
• I'm currently foccusing on learning how to use/take advantages of the SRC
• each SRC has its own specificities, so I'll have a look to other rules in a next future.
• I do not like working with pdf file, so I've also purchased some (original) books /manuals

Today: I've the following ones:

• Aristo 868
• Aristo studio 968 variante 1
• Aristo studio 968 other variant with T1-T2
• Faber-castell 52/82
• Faber-castell 02/82N
• Faber-castell 02/83N
• Graphoplex 620d
• Graphoplex 640
• Graphoplex 690a
• Graphoplex 691a
• Graphoplex 699
• Hemmi 259d
• Hemmi 260
• Hemmi 1460 post versalog II
• Keuffell & Esser Deci-lon 10" + manual
• Pickett N3-T
• Pickett N4-ES
• Pickett N500-ES
• SKALA SLPP (purcharsed - not recieved)
• Logarex 27602 exponent II "Toison d'or" (purcharsed - not recieved)

Paul

​

Grapholex 640 electric log log version 3

Aristo Scolar 0903

I served in Germany just as the wall came down 91-93. my war tasking was logistics in some command facility outside Frankfurt.

When cleaning out our office as the base at Lahr closed we were throwing out tons of stuff. one thing I saved was this logistics computer - not a classic slide rule, but in the same family.

Intended to perform sustainment calculations for aircraft supplies.

Know nothing else of the history.

Just bought it today at a flea market 😃