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Hemmi Slide Rules

Hemmi was the largest manufacturer of slide rules, and is estimated to have sold some 15 million rules over its lifetime. These were sold under their own name (Sun) as well as redistributed for a large number of other companies, most notably the Frederick Post Co. in the US and the Hughes Owens Co. (also known as Geotec) here in Canada. Reflecting their Japanese origin, these rules were often made of bamboo with celluloid facings, which worked out very well since bamboo is naturally self-lubricating and withstands changes in temperature and humidity better than other types of wood. Their Versalog model, made exclusively for Post (model 1460) and Hughes Owens (1777 or 341 3010) is one of the most popular rules of all times, along with the K&E 4081-3 and Faber Castell 2/83 series. Hemmi also made a number of plastic rules, which were generally of very high quality and compared well to other manufacturers. Given their extensive range of products, it is not surprising to see a number of specialized rules out there as well. Interestingly, Hemmi still exists today, but makes only hydraulic and related engineering components.

Although Hughes Owens began importing Hemmi rules long before Post, these Japanese-made rules were naturally unavailable to local distributors during WWII. According to Paul Ross and Ted Humesresearch project, by 1946 these rules reappeared with the label Made in Occupied Japan which was eventually dropped to Made in Japan around 1951. Also around this time, they started engraving 2-letter date codes on all their rules representing the year and month they were made. The first letter corresponds to the year starting with B for 1951 and ending with Z in 1975. The second letter corresponds to the month, with A for January, B for February, etc. Although the date codes were prominently engraved and paint-filled in the early years, from the late 1950s onward they can be hard to spot as they are only lightly engraved in small letters, often near an edge. According to John Spiveysresearch projecton Hughes Owens, the switch from the old 17xx series nomenclature to the new 341 xxx series took place between June and August 1964. Moreover, Hughes Owens also adopted the brand name Geotec for its slide rule and drafting products somewhere between June 1968 and May 1969.

I am working on an upcoming Slide Rules in Canada page that will feature more information about the Hughes Owens company and its products, including the various catalogs in my collection. Please stay tuned!

(later HO/Geotec 341 3010, identical to Post 1460)

The premiere slide rule made by Hemmi, this model is better known as the Post Versalog 1460 (this specimen is actually the second version for the original Versalog model, generally designated as Ib). Ive a fondness for rules used in Canada, though, hence my preference for Hughes Owens models. This particular specimen is in excellent shape, as both the rule and case look as though theyve barely been used (date code ME, or May, 1962). In fact, the virtually unmarked leather case still has that new leather smell (I guess youll just have to take my word for it). The rule has a good solid feel and slides very easily, although I think I still prefer the mahogany look of the K&E models. According to my 1958 price list, this rule cost $25 CDN back in those days … which, after adjusting for inflation, is considerably more than what I paid for it today. Thecasehas the smart adaptation of a little clear plastic window under the flap in which to put your vital statistics. Seems like a good idea, rather than marking up the leather. I dont know about you, but Id hate to lose a rule like this! Incidentally, this style case cost $7 CDN all by itself in 1958. Ive also obtained the Hughes Owens versions of the hard-cover Versalog instruction books, both the first (1951) and second (1963) Canadian editions shown above. They are identical to the Post versions except for the Hughes-Owens name everywhere (check out mySlide Rule Bookspage for more info). Ive also managed to pick up a Hemmi slide rule magnifier for this type of cursor – it looks a bit silly on top, but zooms in quite nicely. Although these only used to cost $3 CDN, Ive seen them fetch over $100 CDN on auction in recent years. Odd that they are now worth considerably more than the actual rule … this is indeed a strange business!

(formerly HO 1778, identical to Post 1461)

The pocket model of the infamous Versalog slide rule, this one is from a bit later in the design cycle but with the same scale set as the above full length version (date code on this rule is RE). Indeed, apart from its diminutive size there is no real difference between this rule and its full-size sibling. The pocket case is the late model all-leather version, with the name Hughes-Owens imprinted directly on the leather in a stylized font. A very popular and sought after rule, I managed to snag this one in the original box with hard cover manual shown above. Interestingly, this version of the HO Versalog manual is in French, and was clearly prepared for the French Canadian market here in Quebec. More information about this find will be presented shortly on my upcoming Slide Rules in Canada page. Im not sure how much these rules retailed for back then, but I can assure that you they typically cost considerably more than the more common full size versions now-a-days!

(later HO/Geotec 341 3120, identical to Post 1450)

The little brother to the Versalog, this rule is of approximately the same vintage as the earlier Versalog Ib on this page (date code MD, pinning it to April, 1962). It has less scales overall (and presumably was less expensive at the time), but has the addition of a few specialized trigonometric scales. Virtually identical in construction to the Versalogs, although this one has a simpler black leather case which seems inferior compared to the richly coloured Versalog case shown above. Unfortunately, the stitching has all come loose, and has been clumsily repaired with glue (which has also broken apart). The belt clip is still intact, though. An incredibly useful adaptation, but I think Id feel pretty silly walking around with one strapped to me today! Reminds me too much of a lightsaber: An elegant weapon, for a more civilized age ….

(formerly HO 1776, identical to Post 1450)

Right on the cusp of the name change to Geotec (date code SF), this rule is identical the earlier 1776 presented above. The case, however, is the late model all-leather type very similar to the contemporary pocket Versalog on this page. Interestingly, the instruction manual has both the Hughes Owens name and Geotec logo shown on the cover. Inside the manual, the diagram of the rule features the Hughes-Owens name on the stator and the Geotec logo on the slider, despite the presence of the HO logo on this particular rule. I know it wasnt long before the Geotec brand name and logo replaced the Hughes Owens labels on the actual rules … clearly, this specimen represents the very beginning of the shift in HO/Geotec labels. Also included in its own scan up above is the warranty/care and maintenance insert that was sold with high-end HO rules. A very nice rule, and rare to find during that tumultuous time of name brand transition.

A most unusual (and rare) rule. I obtained this rule from John Spivey, resident Hemmi/Hughes Owens expert (you can see scans of the same rule on hisresearch projectat Spheres Slide Rule Universe). The 1773 is distinctive for the simple reason that it doesnt show up in any of the known Hughes Owens catalogs! The 1928 catalog lists an all-metal 1773 model (no picture given), but the model number was unheard from that time onward. The 1958 catalog makes no mention of it, and the 1967 catalog (by which time they had switched to the 7 digit numbering scheme) shows no equivalent model either. Needless to say, a very short lived intermediate! Helping to date the rule is the engraved KI date code and standard dark brown case contemporary for the time period (thoughtfully embossed THE HUGHES OWENS CO. LTD. 1773). The case is also hand-dated to Nov. 6, 1963 by one S. Werner. The scale arrangement is identical to the Hemmi 251, and is actually a very useful organization, in my opinion. Quite a nice rule, but I guess there wasnt much of a market for this type of medium-grade high-end rule, given all the versalogs and versatrigs out there. An interesting evolutionary throwback … as always, if anyone knows more about this particular model, please drop me a line.

(formerly HO 1772, identical to Post 1444K)

This is an adorable little bamboo rule. A very late model pocket slide rule, of the Post 1444K type. One dead giveaway to its more recent origin is the plastic cursor, which wasnt introduced until towards the end of Hemmis slide rule production run. Its still very nice, with a smooth spring and nice grip, and slight magnification due to the curvature of the face. The other giveaway is the Geotec name and new numbering 341 000 numbering format. Finally, the date code of UG places at July, 1970. The rule is in near mint condition, as is the leather case that snugly surrounds it. Incredibly lightweight, but infinitely nicer than any of the all-plastic pocket rule Ive seen. This one has replaced thePickettMicroline 160C-ES as the one I carry around with me in my knapsack. Im not sure how much it was selling for in 1970, but the earlier H-O 1762 version sold for $4.25 CDN in 1958.

(later HO/Geotec 341 3215 Universal, identical to Post 1452)

Similar in design to theK&E 4053-3, but with a little more flourish. Like the K&E Polyphase model, the 1771 also contains inch and metric rulers on the edges and a cheat sheet on the back, although in plastic in this case instead of paper. Also, note the internal scale behind the slider on the third scan. Unfortunately, the bamboo is almost completely covered by celluloid, with the exception of the exposed ends of the rule. Still a very solid and professional looking slide rule. As for the age, I now know that this body design was used in the 1930s and 40s, and was definitely gone by the 50s (I used to think it was more recent). The cursor is the later model metal-framed glass, which I believe came into play sometime shortly before the second world war. The rule is labelled Made in Japan, fixing it either to pre-1941 or post-1951. Add to that the fact that I cannot find a date code no matter how hard I look, and I would have to conclude that this rule is from the period immediately preceding WWII, say circa 1940. If anyone has a better guess, please let me know. One thing I really like about this particular rule is the case … as you can see from the high resolution scans, its taken a pretty good beating and the stitching has come loose is one spot. But the leather is beautifully worn and fits very snugly around the rule, like a glove. This is one case that has done its job well!

Update: Thanks to Dieter von Jezierskis slide rule book, Ive discovered that the quotient and product notation on this slide rule (along with the early digit-recording cursor that went with it) was developed by Faber in 1905 as an aid in keeping track of decimal points. Faber abandoned it by WWI, as apparently it was considered too difficult for most people to use. Hemmi continued the practice to at least 1940, although I know they dropped the corresponding cursor design a little earlier, as evidenced by this model. Check out Dieters book (listed on mySlide Rule Bookspage) to learn more about how to use these interesting features.

This rule demonstrates that K&E wasnt the only slide rule maker to radically change their designs without changing the model number! Differences between this rule and the 1771 presented above abound. To start, it is a full centimeter longer, 3/4 of a centimeter wider, and about twice as heavy. The cursor is also considerably larger, and it lacks the internal ruler under the slider. Interestingly, the trig sine scale on this model goes from 6 up to 90 degrees, compared to 1 to 75 on the older version (the trig scales are also upside down on this one, compared to the other). The table of equivalents on the back has the same basic information, and is similarly worn, but uses a different font and is a bit larger in size (personally, I find it looks more old-fashioned). The edge rulers are also slightly different, as this one leaves a wider blank margin at either end. Interestingly, the date code of CF (June, 1952) on this specimen is clearly visible on the high resolution scans as it is filled in with ink and located after the Made in Japan label. I wonder how long they did that before burying it in small engraving near the edge? As for the leather case, it is larger, harder, darker coloured, and now with embossed lettering instead of gold. Frankly, I must say that I prefer the quality of the older leather cases! Ah well, thats progress for you. Incidentally, Ive recently discovered that this model rule sold for $8.50 CDN in 1955-58, which was definitely a bit cheaper than the equivalentK&E 4053-3of the same time period (mind you, Im not sure of the exchange rate back in those days). If I find out any more, Ill let you know …

Here we go again … another version of the 1771. In this case, very similar to the model presented above, but with a few slight changes. Superficially, the patina on this specimen is clearly much whiter, although it has some red ink discolourations along the inch ruler edge. The rule itself differs only on the reverse of slider, where the trig scales are much closer to the first 1771 listed on this page. The cheat sheet on the back is the same in content as the other two, but in better shape, and with a change to a more modern looking font. The date code is NH, dating this rule to August, 1963. I havent bothered scanning in the edge or inside views, as they are identical to the later one above. The case is also very similar to the one above, but it does seem to have a bit of a cheaper feel to it (not to mention some sort of black tar stain on the front). Im going to keep my eyes open for more 1771s to add to my collection … Ive seen pictures of other models that were different from all three here. Ill keep you posted …

(later HO/Geotec 341 3526, identical to Post 1447, Hemmi 40K)

Ive picked up several of these as gifts for friends, as I find they make excellent beginner slide rules. This student model rule features celluloid laminate over bamboo, and all the exposed bamboo on the back gives it a lovely look and feel. Although I dont have the case for this particular rule (date code MD, same as the Versatrig 1776 on this page), they typically come in two-piece, dark blue, hard cardboard cases with the Hughes Owens name and model number stamped in gold lettering. Later versions come in the standard Hemmi two-tone blue/white plastic cases with the Geotec logo. Ive included a copy of the standard Post 1447 instruction booklet up above, but more interesting is the French version of the Hughes Owens 341 3526 instruction manual prepared for the Quebec market. Aside from the illustration of the rule and the French HO warranty card inside, there is no mention of Hughes Owens anywhere in this manual! It even goes so far as to refer to the rule as a Hemmi No. 341-3526, despite the fact that that designation clearly belongs to HO/Geotec and NOT Hemmi (its actually a Hemmi model 40K, by their nomenclature). In any case, I think youll find that these rules are fairly easy to come by and still relatively inexpensive – they only sold for $3 CDN in 1958, and can usually be found for about $10 today. Highly recommended if youre just starting out!

(Identical to Post 1458, Hemmi 150, virtual clone of K&E 4088-3)

Unfortunately in poor shape, this is a rather obscure early model duplex Hemmi slide rule. It is virtually identical to theK&E 4088-3in my collection (except for the bamboo, in this case). Based on its similarities to that model (even the cases are similar), I had originally estimated it from the same time period, namely mid to late 1920s. However, it is not listed in the 1928 H-O catalog, and apparently wasnt sold by Post until 1932. It does match the illustration of the 1937 H-O catalog, however. So, for now, Ive assigned it an approximate date ca. 1935. Whatever its age, it has certainly taken a beating … the frameless cursor glasses are cracked through on both sides, allowing the cursor assembly to fall right off! Clearly not the greatest design, which presumably explains why all the major slide rule manufacturers abandoned it for a modified cursor design by the late 30s. A very old-fashioned look and feel …

(may be a Hemmi 34, unknown Post equivalent)

A fascinating (and rare) little slide rule. Dating this particular specimen is especially difficult, as this model is only listed in the three earliest Hughes Owens catalogs, and doesnt exactly match any of the illustrations. It most closely resembles the first listing in 1914, and given its general design features Ive given it an approximate date of ca. 1915. Unfortunately, the cursor is missing, which would have helped pin the date down a little. This rule predates Post involvement with Hemmi, and thus there is no Post equivalent that Im aware of. John Spivey, in consultation with Paul Ross, informs me he thinks this may be a Hemmi 34, and I tend to agree based on whats known about that model. The rule features basic scales, including S,L,T on the reverse of the slider, along with inch and centimeter scales. Note the presence of Japanese script on the inside face of the rule, beneath the slider. The table of contents on the back differs from later models, and includes such interesting measures as the Ultimate Strength of various woods and metals in pounds per square inch. In fact, this table seems to be virtually identical to my earliestFabermodel. One of the other interesting aspects is the case, made of dark blue fabric-covered card/particleboard with a snap closure. Imprinted in gold lettering on the flap is the Hughes Owens name and model number, along with the words HEMMIS SLIDE RULE on the brass button. A most unusual find, and clearly my oldest Hughes Owens rule to date.

One of the last rules Hemmi ever made, and one of their best desktop models. Accurately billed as an advanced Darmstadt, Hemmi took the classicFaberDarmstadt design and actually improved on it in several ways. Made of celluloid on bamboo, this rule features Fabers extended scale style (although sadly not the self-documenting feature) and a better scale arrangement than any other simplex rule Ive ever seen. It also sports Fabers useful P scale, with S&T scales moved to the front of the rule, and a new BI scale added (an inverted B scale for squares and roots, although I dont find it terribly useful). More importantly, all the known log-log scales have been added andplaced togetheron the back of the slide (why didnt anyone ever think of this before?). A centimeter ruler adorns the slanted edge and a standard cheat sheet is on the back. Oddly, Hemmi left the hard edge blank … would it have killed them to put an inch ruler there? Actually,Darren Samphierwith whom I swapped a K&E 4081 for this rule, tells me that hes actually seen a couple of 130Ws that do have an inch ruler, but the vast majority of them dont! Odd … but still a minor quibble for such a well-designed rule. Like the Faber 1/54 Darmstadt andEco Bra 1461, this rule also sports a multiple hairline cursor, in this case with two additional cursor lines for calculating the area of a circle from its diameter and doing HP/kW conversions. The domed plastic cursor also has a slight magnification effect, just like on the pocket Geotec rule above. The rule came MIB still sealed in its original plastic bag (although I couldnt resist opening it up and playing with it!). The set is complete with Hemmis two-toned plastic case, manual and original cardboard box. Incidentally, I believe Darren still has more 130Ws to trade. The date code of WG places it to July, 1972. A pity they didnt keep making slide rules for a little bit longer … I would love to have seen what else they might have come up with!

The smallest functional slide rule Ive ever seen! This diminutive pocket model sports a built-in domed magnifying cursor and a beautifully worn Post leather case. Like the Geotec 341 3425, it is made of celluloid laminate over bamboo, and lacks any type of cheat sheet on the back. Given the Made in Occupied Japan label, and the presence of the CI scale, that would seem to narrow the date to around 1949-1951, according to Paul Ross and Ted Humes research project. Although a bit too small to really be all that useful in everyday life, this rule probably attracts more attention in my collection than any other! Frankly, its just too cute for words! Incidentally, the Hughes Owens equivalent model (1760) sold for the same price in 1958 as the 1762-type shown previously on this page (namely $4.25 CDN).

Page last updated on June 17, 2002 –

All material © 1999, 2001 by Eric Marcotte, Ph.D.

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