16 Matching Annotations
  1. Jan 2024
    1. 1956 --- The ST scale on rules that had Decimal Trig scales were converted to an SRT scale.
    2. 1956 0 88,500 88,500

      My 4181-3 slide rule was likely manufactured in 1956 as it has the SRT scale initiated in 1955 and has a serial number 004365 which is in the series 3 segment which reset in 1956 and ran from 0 to 88,500 that year.


    1. 1955b - The scale set was changed. ST scale was changed to SRT on the 4081s only.

      My 4181-3 was likely made in 1955 or after as it has the SRT and not the ST scale. (It has a 1947 copyright mark on it.)

    2. 1955b (4081-3, 4081-5, 4181-1, 4181-1C, E4181J, 4181-3, 68 1200, 68 1205, 68 1210, 68 1215, 68 1220, 68 1251, 68 1256, 68 1261, 68 1282, & 68 1287) Scale sets: Front: LL02 LL03 DF = CF CIF CI C = D LL3 LL2 Rear: LL01 L K A = B T SRT S = D DI LL1

      These are the scale sets on my K+E 4181-3 slide Rule

    1. 4181-3 10" Log Log Duplex Decitrig Plastic 4081-3 family

      The Keuffel & Esser 4181-3 was part of the 4081-3 family and was described in their catalogs as a 10 inch Log Log Duplex Decitrig Plastic slide rule.

      via https://www.mccoys-kecatalogs.com/KEModels/kexrefmain.htm

    1. Either index may be used.

      If the numbers to be multiplied result in the hairline not being able to be used because the reading is off one side of the slide rule, then use the second index (the number 1) on the D scale.

    2. To find the product of two numbers, disregard the decimalpoints, opposite either of the numbers on the D scale set the index ofthe C scale, push the hairline of the indicator to the second numberon the C scale, and read the answer under the hairline of the D scale.The decimal point is placed in accordance with the result of a roughcalculation.
    3. Definitions. The central sliding part of the rule is called theslide, the other part the body. The glass runner is called the indi-cator and the line on the indicator is referred to as the hairline.
    4. Kells, Lyman M., Willis F. Kern, and James R. Bland. K+E Slide Rules: A Self Instruction Manual. New York: Keuffel & Esser Co., 1955.

    5. Accuracy of the slide rule. From thediscussion of § 2 it appears that we read fourfigures of a result on one part of the scaleand three figures on the remaining part.Assuming that the error of a reading is onetenth of the smallest interval following theleft-hand index of D, we conclude that theerror is roughly 1 in 1000 or one tenth of oneper cent. The effect of the assumed errorin judging a distance is inversely propor-tional to the length of the rule. Hencewe associate with a 10-inch slide rule anerror of one tenth of one per cent, with a20-inch slide rule an error of one twentiethof one per cent or 1 part in 2000, and withthe Thacher Cylindrical slide rule an errorof a hundredth of one per cent or one part.in 10,000. The accuracy obtainable withthe 10-inch slide rule is sufficient for manypractical purposes; in any ease the sliderule result serves as a check.

      The accuracy of most 10 inch slide rules is approximately 1 in 1000 or one tenth of one percent.

      Because the error in approximating distance is inversely proportion to the length of a slide rule, longer slide rules will have proportionally smaller errors, so while a 10 inch slide rule has an error of 1 in 1000, a 20 inch will have an error of 1 in 2000 and larger rules can be accurate to within 1 in 10,000 or better.

  2. Aug 2023
  3. Mar 2022