Barth's alpha slide rule for milling and gear cutting
Date: circa 1910
Inventory Number: 1990-5-0016
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 x 28.4 x 5 cm (1/2 x 11 3/16 x 1 15/16 in.)
Description:
Wood rule with three slides, faced with off-white paper on top. The top and bottom slides are fixed; the second slide moves to left and right.
Printed on the bottom edge of the top slide is a scale for "DIAMETER OF CUTTER = D," with values descending from 50'' to 1/2''. The second, moveable slide is printed with two scales. On the top edge is one for "DEPTH OF CUT = H," with values descending from 5'' to 3/64''. Near the center of the slide is printed a scale for "DIAMETRICAL PITCH," carrying values from 1/2 to 40. Between the marks for 8 and 9 is an arrow pointing towards the third slide.
The top edge of the third slide is printed with a scale for "(alpha) = 2 {(square root)[(H/D)(1-H/D)]}," carrying values from 0.14 to 1.
Printed on the bottom edge of the top slide is a scale for "DIAMETER OF CUTTER = D," with values descending from 50'' to 1/2''. The second, moveable slide is printed with two scales. On the top edge is one for "DEPTH OF CUT = H," with values descending from 5'' to 3/64''. Near the center of the slide is printed a scale for "DIAMETRICAL PITCH," carrying values from 1/2 to 40. Between the marks for 8 and 9 is an arrow pointing towards the third slide.
The top edge of the third slide is printed with a scale for "(alpha) = 2 {(square root)[(H/D)(1-H/D)]}," carrying values from 0.14 to 1.
Signedtop slide, on right: Carl G. Barth.
Inscribedtop slide, on left: MILLING & GEAR CUTTING. DETERMINATION OF (alpha) FOR FEED.
FunctionFor calculating the constant alpha, from which the appropriate feed for gear-cutting or milling can later be determined (using Barth's gear cutting feed rule, see 1990-4-0006, 1990-4-0007, 1990-4-0008; or Barth's milling feed rule, see 1990-5-0010, 1990-5-0011).
The user first moves the center slide to left or right such that the appropriate value for either depth of cut or diametrical pitch (according to available information) coincides with the cutter's diameter (top slide). Keeping this (second) slide in place, he locates the value of alpha on the third slide to which the arrow on the bottom edge of the second slide points.
The user first moves the center slide to left or right such that the appropriate value for either depth of cut or diametrical pitch (according to available information) coincides with the cutter's diameter (top slide). Keeping this (second) slide in place, he locates the value of alpha on the third slide to which the arrow on the bottom edge of the second slide points.
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;
Used to determine alpha for Barth's gear cutting and milling feed rules, see 1990-4-0006, 1990-4-0007, 1990-4-0008, 1990-5-0010, 1990-5-0011;
Identical in function to 1990-5-0007, 1990-5-0008, 1990-5-0009, though of different dimensions.
Used to determine alpha for Barth's gear cutting and milling feed rules, see 1990-4-0006, 1990-4-0007, 1990-4-0008, 1990-5-0010, 1990-5-0011;
Identical in function to 1990-5-0007, 1990-5-0008, 1990-5-0009, though of different dimensions.
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.
