Barth's classification slide rule for carbon steels
Date: circa 1910
Inventory Number: 1990-5-0019
Classification: Slide Rule
Subject:
Maker: Carl G. Barth (1860-1939)
Associate Name: Frederick W. Taylor (1856-1915)
Cultural Region:
Place of Origin:
Dimensions:
1.3 × 20.6 × 4.8 cm (1/2 × 8 1/8 × 1 7/8 in.)
Description:
Rectangular slide rule with three slides, faced with off-white paper. The top and bottom slides are fixed; the second slide moves to left and right.
The bottom edge of the top, fixed slide is printed with a scale for "E = PERCENTAGE OF ELONGATION," carrying values from 1 to 50. Printed along the top edge of the second, moveable slide is a scale for "S = TENSILE STRENGTH IN THOUSAND POUNDS," with values ranging from 40 to 120. Along the bottom edge of the same (second) slide is printed an unlabeled scale carrying values from 100% to 200%. Superimposed on the 100% hash mark is an arrow pointing towards the third slide.
The top edge of the bottom, fixed slide is printed with a scale for "V = STANDARD CUTTING SPEED," carrying values from 50' to 210'. Directly below this scale is another, for "HARDNESS CLASS NUMBER." The class number scale has values descending (in whole numbers) from 28 to 0.
The bottom edge of the top, fixed slide is printed with a scale for "E = PERCENTAGE OF ELONGATION," carrying values from 1 to 50. Printed along the top edge of the second, moveable slide is a scale for "S = TENSILE STRENGTH IN THOUSAND POUNDS," with values ranging from 40 to 120. Along the bottom edge of the same (second) slide is printed an unlabeled scale carrying values from 100% to 200%. Superimposed on the 100% hash mark is an arrow pointing towards the third slide.
The top edge of the bottom, fixed slide is printed with a scale for "V = STANDARD CUTTING SPEED," carrying values from 50' to 210'. Directly below this scale is another, for "HARDNESS CLASS NUMBER." The class number scale has values descending (in whole numbers) from 28 to 0.
Signedface, top slide, left: BARTH'S CLASSIFICATION SLIDE RULE / FOR / CARBON STEELS.
Inscribedface, top slide, right: V = (CONSTANT)({1-[7/(10+E)]}/{S-30,000})
FunctionFor determining the standard cutting speed, and corresponding hardness class number, of carbon steels.
The user first moves the second slide to left or right such that the appropriate value on the elongation scale (top slide) coincides with the appropriate value on the tensile strength scale (second slide, top edge).
Holding the second slide in place, he locates the value on the cutting speed scale (bottom slide) that coincides with the 100% arrow on the unlabeled scale (second slide, bottom edge). This indicates the standard cutting speed for the material in question. (If, due to the position of the second slide, the 100% arrow falls outside the cutting speed scale, the user reads off one of the other hash marks on the unlabeled scale [second slide, bottom edge], then transforms the velocity accordingly. For example, if he reads V = 20' off the 160% mark, the standard cutting speed is 20'/1.6 = 12.5'.)
The hardness class number is that value on the bottom scale of the third slide which comes closest to coinciding with the standard cutting speed, as determined by the above operation.
The user first moves the second slide to left or right such that the appropriate value on the elongation scale (top slide) coincides with the appropriate value on the tensile strength scale (second slide, top edge).
Holding the second slide in place, he locates the value on the cutting speed scale (bottom slide) that coincides with the 100% arrow on the unlabeled scale (second slide, bottom edge). This indicates the standard cutting speed for the material in question. (If, due to the position of the second slide, the 100% arrow falls outside the cutting speed scale, the user reads off one of the other hash marks on the unlabeled scale [second slide, bottom edge], then transforms the velocity accordingly. For example, if he reads V = 20' off the 160% mark, the standard cutting speed is 20'/1.6 = 12.5'.)
The hardness class number is that value on the bottom scale of the third slide which comes closest to coinciding with the standard cutting speed, as determined by the above operation.
Historical AttributesThis is part of a set of slide rules for machine shops designed by Carl G. Barth under Frederick Winslow Taylor's system of scientific management. Given the characteristics of a particular machine and a depth of cut, for example, a shop manager could quickly calculate the most efficient speed and feed settings using one of Barth's speed and feed slide rules. Other objects in the collection include slide rules for helical springs, belts, and gears, as well as jigs for making slide rules.
Curatorial RemarksRecords indicate that Barth was working in Philadelphia at the time;
Identical to 1990-5-0017 and 1990-5-0018.
Identical to 1990-5-0017 and 1990-5-0018.
Primary SourcesCarl G. Barth, "Slide Rules for the Machine Shop as a Part of the Taylor System of Management," Transactions of the American Society of Mechanical Engineers 25 (1904): 49-62.
Frederick W. Taylor, "On the Art of Cutting Metals," Transactions of the American Society of Mechanical Engineers 28 (1908): 31-432.
Frederick W. Taylor, "On the Art of Cutting Metals," Transactions of the American Society of Mechanical Engineers 28 (1908): 31-432.
ProvenanceThe papers and slide rules of Carl G. Barth and his son, J. Christian Barth, were transferred to the Baker Library of the Harvard Business School by J. Christian Barth in 1961.
The slide rules were transferred from Harvard Business School to the Collection of Historical Instruments in 1980.
The slide rules were transferred from Harvard Business School to the Collection of Historical Instruments in 1980.
