**Last Updated: 7/9/15**

N902-ES demonstration rule added.

This was the first rule I got. I'm not sure if I found it in my grandpa's basement or at a clearance store, but I know I was about 14-15 when I got it and started to try and puzzle it out.

Another of Pickett's fine alumnimum rules, this one has the standard A, B, C, D, CI, K and L scales on one side. On the other, however, it has several scales intended for the businessman or shopkeeper, including the C% and R% scales for calculating percentages (percent increase, percent discount). Comes in the same sort of nifty scabbard as the N600.

I got this rule from Dave Crate in exchange for listing his page on mine (since, due tot he age of my page, it had good search engine penetration), and it really kicked off my serious acquisition of slide rules, between my showing the rule around and the attention I got from a newspaper piece soon after.

Slightly larger than the Engineer's Metric Converter, this rule is by a
company I'd not heard of before (made in Germany by Dennert & Pape), although
I've since seen plenty of Aristo rules. On the
side scanned, it has C, CF, CI, CIF, D, DF, K and L scales. On the other
side are A, B, C, LL0, LL1, LL2, LL3, S and T. It comes in a slim box that
is capped at one end.

Acquired as part of the "Walker Collection," a batch of slide rules I got all
at once when my appearance in the newspaper caused a woman to recall her
husband's slide rule collection and decide that I might appreciate it.

My second Aristo rule, this one apparently manufactured in Germany by Charvoz. It was a going-away gift from Dr. Benenson, one of my bosses during the two years I worked at Michigan State University's Lyman Briggs School, it was his first slide rule in high school/college. The front side (top half of the image) has K, A, B, T, ST, S, C, D, DI and LL0 scales. The back side has LL01, LL02, LL03, DF, CF, CIF, L, CI, D, LL1, LL2, LL3 scales. The rule's a bit longer than my current scanner, so the ends were cut off. The front side has raised "bumpers" at each end that connect the fixed parts together. On the right side of each scale is the mathematical operation for that scale. "DBGM" is printed on the back of the cursor and the front right end of the center stick, unsure what it means. The cursor itself is two plates of clear plastic spaced apart by aluminum top and bottom pieces. It has a Watts to Horsepower conversion on the front, and two more hairlines on the cursor whose purpose I haven't figured out yet. The one on the A/B scale has a separation that represents a multiple of about 1.28, and the one on the CD scale a multiple of 1.13. Going from the A/B to the C/D multiplies by 1.274 and then takes the square root. Huh. Came in a hard leather scabbard.

Thanks to Stefan Vorkoetter for explaining some of the mysterious gauge lines. This site has more on them in general, and 1.28 bit above is 4/pi, with 1.13 useful for calculating the volume of a cylinder. Another of the lines lets you convert radius to area for a circle: place the main hairline on the radius on the A scale, and the other line will show the area on the D scale.

A very cheap student rule made by Pickett, with A, B, C, D, CI, K, L, S and T scales. One-sided. Traded one of several Microline 120s I got in the wake of the newspaper article for this.

A fairly basic one-sided plastic rule, with A, B, C, D, CI, K, L, S and T
scales. Cheaply made, the center stick doesn't always line up when flush
against the ends of the rule, but it can be used for basic learning and so
forth. I got a bunch of rules from a man near town in the wake of being in
the newspaper, and three of this rule came as part of the deal.

I have since also acquired a yellow version of this (not scanned), which used
to be the official "loaner" rule for Engineering Physics 2 at Kansas State
University. And I use it occasionally for that purpose, to encourage
students to remember their calculators....

A 2001 eBay purchase, this is a fairly simple trig rule, but it came with all the packaging and paperwork, including the warranty card. Not shown is the back of the rule, which has a sort of cheat-sheet for operation of the rule. Page down a bit to see the classroom demonstration version I acquired in 2015.

This rule actually came as part of a book entitled __The Slide Rule And
How To Use It__, published by Grosset and Dunlap in 1942. It's a workbook
with a small box glued to the inside front cover containing the rule pictured
above. It's a very basic learning rule, with only A, B, C, D, CI and K
scales on a rather cheap painted softwood. The back has a number of
conversion tables and useful information (such as the weight of a cubic inch
of "wrot" iron). One interesting feature is the cylindrical magnifier over
the center of the cursor.

I got this as part of the same deal that included the 120s. However, I have
since seen eBay infested with these cheap rules, often advertised as "Antique
Wooden Slide Rule!" Hard to get more bottom of the line than the Lawrence
rules, tho.

But you can certainly try. Still in original packaging, this sold for $1.37 back in the day. Extremely basic, only A, B, C, CI, D, and K scales.

A very nice two-sided long plastic rule, complete with mathematical notation (as on the Pickett N-515T) to explain the use of the rule. Has scales: A, B, C, CI, CF, CIF, D, DI, DF, K, L, S, ST, T, LL1, LL2, LL3, LL01, LL02, LL03. Obtained on eBay.

Another very nice two-sided plastic rule. It lacks the LL01-03 scales of the Sterling, but it has two T scales (T1, T2). The green background on some scales is a nice touch. The cursor has multiple hairlines, many of which I can't figure out, but two of which are clearly a way to quickly convert from kiloWatts to horsepower. Bought on eBay.

It has a cracked window and needs some cleaning, but this big Sun Hemmi bamboo rule is otherwise pretty nice. The front has LL0, LL/0 (LL00 in more standard notation, the inverse line), K, DF, T, ST, S, C, D, R1 and R2, L. The back has LL/1, LL/2, LL/3, CF, CIF, CI, C, D, LL3, LL2, LL1. And, um, yeah, I think the stick was in backwards when I took the picture. Makes more sense to have CF and DF on the same side. Oddly, there's no A or B. R1 the square root of C, R2 extends that scale (so 9 on C gives 3 on R1 (square root of 9) and 9.49 on R2 (square root of 90)). Bought on eBay.

Circular Slide Rule

Circular Slide Rule

A single, immovable and rigid celluloid-coated aluminum disc with two cursors on one side and one cursor on the other. Most of the scales are unlabeled on the front, and I have no idea what the V versus U.S.S. scale is, or what the scale with letters rather than numbers is for (it does not seem to be a scale for setting the two cursors). The reverse side has multiple sine and tangent scales, plus conversion from fractions to decimal. The case is imprinted "A&B Smith Co." but that's no guarantee that this is the company that made the rule. While there are copyright dates (1936 for the front, 1931 for the back) there's no name of manufacturer. I have since found an eBay auction for another of these that claims it to be a Dietzgen Midget Slide Rule, and I got the seller to send me photocopies of the instructions so I know that V and U.S.S. are screw threading/tapping size systems.

Stefan Vorkoetter points out that the scale just inside the B scale converts hours on B into minutes on the inner scale. Other front scales convert indicated and true airspeed (correcting for altitude, as airspeed indicators are sensitive to pressure differences). On the back are windspeed compensation calculators (as Stefan writes about here), and scales for finding vector components (TAS arrow on x, look next to the degree mark d to get x sin(d) or x cos(d) depending on whether you're looking at the black on white or white on black marks).

Another aviation rule, I got this one from American Science & Surplus. It's made by Cruver Manufacturing Co., and is a spiral rule that lets you figure out true altitude from indicated altitude by compensating for temperature. The only instructions are printed on the back, and I never quite managed to make it work in a sensible manner. But I don't really have avionics training.

This rule is 22" long, and comes in a wooden box with latches to hold it in. Once removed from the box, it has metal legs it stands on. Designed for everyday simple jobs, it only has the C, CI, CF, D and DF scales. But with a single decade spanning 20", it gives pretty good precision. Being made of wood, however, it has warped slightly with age, so the precision isn't what it used to be. It comes with an instruction pamphlet extolling the virtues of the slide rule for use in the average merchant's shop. Part of the Walker Collection.

Purchased on eBay, this is a set of slide rules used by artillerists to aim their big guns. Based on the materials, I'm guessing it's Vietnam vintage or thereabouts. The small rule at the top is the only "slipstick" style, and seems to be a rough approximation rule, with the cursor sticks below it used for specific loads and uses. It seems like I'd need specially made charts in order to get any use out of these rules, though.

I got this clasp on eBay missing the clip part (although I've since seen this model complete on eBay). I bought a cheap tie clasp and kitbashed the pieces together to create the thing seen above. It only has A, C and D scales, plus a cursor, and is 2" (5cm) long.

Grant Pilkay sent me this book with included rule, meant to help calculate the effects of nuclear blasts. Sadly, some of the paint bound to the wrong side of one of the wheels and peeled off, so turning the wheel shows a gap. Click on the image to see at full size.

After years of trying, including some bot-sniped attempts on eBay, I finally got a demonstration rule for a price I could afford. It helped that "a price I could afford" went up recently. Pictured in my office, with the regular-sized N902-ES tucked onto the left-hand stand.

Like the proportion wheel, this is another "hidden" slide rule. Sold by Chadwick-Miller (probably an office supply store), it uses two identical cylinder scales to do fixed multiplication tasks, converting units into metric and back to english. Rather than complicate things for the users, the log scales cover three decades explicitly, with things like .5 and 30 on it so users need not mess with order of magnitude estimates. Usually. Inches to feet requires dividing by ten. And the scales aren't lined up as well as they could be, this is just a cheap novelty item, really. The bottom scale is just a linear C/F temperature converter.

A simple metric converter like the pencil cup above. Made by a subsidary of the Borden company, it came in a plastic slipcase and had nothing on the back. In fact, the main body was molded out of fairly thin plastic, which had a broad T-shape cross-section. The back of the center piece has a temperature converter with a few notes like "Freezing" and "Fever."

Same basic idea as the pocket converter, but about twice as long so that you can get more precision. It has a few more unit pairs than the pocket rule: length and area on the front, volume and weight on the back (no temperature). I got this loose (no paperwork or case) from someone who was doing some housecleaning prior to a move. :)

A much more involved metric converter by the same company, it's twice as long as the basic metric converter and has tons and tons of units. Energy, flow, power, heat flow, velocity, density, pressure and so forth. Some of the units I don't even recognize, although the instruction booklet does explain them all.

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