Lesson 46 of Industrial Engineering ONLINE Course
Lesson 3 of Process Industrial Engineering ONLINE Course (Module)
IE Research by Taylor - Productivity of Machining - Part 1 - Part 2 - Part 3 - Part 4 - Part 5
Lesson 3 of Process Industrial Engineering ONLINE Course (Module)
IE Research by Taylor - Productivity of Machining - Part 1 - Part 2 - Part 3 - Part 4 - Part 5
Paper Published in the Proceedings of IISE 2020 Annual Conference.
Frameworks for Productivity Science of Machine Effort and Human Effort
Rao, Kambhampati Venkata Satya Surya Narayana. IIE Annual Conference. Proceedings; Norcross (2020): 429-434.
Research by Taylor Related to Productivity Impact
(B) chemical composition of tool steel: 1 to 7;
280 (B) The chemical composition of the steel from which the V tool is made, and the heat treatment of the tool.
Proportion is as 1 in tools made from tempered carbon steel to 7 in the best high speed tools.
(C) thickness of shaving: 1 to 3.5;
There is a difficulty in understanding research results of Taylor as the folder containing the tables accompanying the paper "The Art of Metal Cutting" is not available in the web. We need to understand what we can from the paper only.
281 (C) The thickness of the shaving; or, the thickness of the spiral strip or band of metal which is to be removed by the tool, measured while the metal retains its original density; not the thickness of the actual shaving, the metal of which has become partly disintegrated.
Proportion is as 1 with thickness of shaving 3/16 of an inch to 3.5 with thickness of shaving 1/64 of an inch.
There is a difficulty in understanding research results of Taylor as the folder containing the tables accompanying the paper "The Art of Metal Cutting" is not available in the web. We need to understand what we can from the paper only.
(B) chemical composition of tool steel: 1 to 7;
280 (B) The chemical composition of the steel from which the V tool is made, and the heat treatment of the tool.
Proportion is as 1 in tools made from tempered carbon steel to 7 in the best high speed tools.
THE CHEMICAL COMPOSITION OF TOOL STEEL
FOLDER NO. 20 GIVING THE ANALYSES AND CUTTING SPEEDS OF MANY OF THE LATEST HIGH SPEED TOOLS, AND A COMPARISON OF THESE TOOLS WITH MUSHET SELF-HARDENING TOOLS AND THE ORIGINAL HIGH SPEED TOOLS AS DEVELOPED BY MESSRS. TAYLOR AND WHITE
1020 The best tool steel should be capable of producing high speed tools of the following qualities or characteristics:
LIST OF THE MORE IMPORTANT CHARACTERISTICS OF HIGH SPEED TOOLS
1021 (A) Tools should be of such composition that comparatively small errors or imperfections in the heat treatment will not seriously injure them and thus render them irregular in their cutting speeds.
That is, the steel should be of that composition from which it is easy to make uniform tools.
1022 (B) Tools should not fire crack easily from the heat treatment.
1023 (C) Tools should be capable of running at the highest standard speed in cutting either hard, medium, or soft steel; or hard, medium or soft cast iron.
1024 (D) Tools should be difficult to ruin on the grindstone or through overheating in the lathe.
1025 (E) Tools should be tough in the body; i. e., not liable to break in use even when receiving severe jars or blows from the work.
1026 (F) Tools should be capable of taking fine feeds in cutting hard metals with proportionally high cutting speeds as when taking coarse feeds.
1027 (G) Tools should be easy to dress or shape without requiring very high heat.
1028 (H) When injured through use in the lathe, the quality of the tool steel should be such that the injury can be repaired by grinding off as small amount as practicable from the tool.
1029 No tool steel has yet been developed which possesses all these qualities in the highest degree. It is, however, a most interesting and useful fact that the tool steel marked No. 1 in Folder 20,
Table 128, possesses all except two of these qualities in as high a degree as any steel that we have tested. The two defects possessed by this steel are that it is rather difficult to forge into a tool; and although it is very tough in its body, it is not as tough as tools whose bodies are either annealed or partially annealed.
(C) thickness of shaving: 1 to 3.5;
281 (C) The thickness of the shaving; or, the thickness of the spiral strip or band of metal which is to be removed by the tool, measured while the metal retains its original density; not the thickness of the actual shaving, the metal of which has become partly disintegrated.
Proportion is as 1 with thickness of shaving 3/16 of an inch to 3.5 with thickness of shaving 1/64 of an inch.
Regarding Thickness of Shaving
289 (A) The quality of the metal which is to be cut is, generally speaking, beyond the control of those who are in charge of the machine shop, and, in fact, in most cases the choice of the hardness of metals to be used in forgings or castings will hinge upon other considerations which are of greater importance than the cost of machining them. This subject will be further treated in paragraph 1129.
290 (B) The chemical composition of the steel from which the tool is made and the heat treatment of the tool will, of course, receive the most careful consideration in the adoption of a standard tool. No shop, however, can now afford to use other than the “high speed tools," and there are so many makes of good tool steels, which, after being forged into tools and heated to the melting point according to the Taylor-White process, will run at about the same high cutting speeds, that it is of comparatively small moment which particular make of high speed steels is adopted. This subject will be further dealt with in paragraph 965, etc.
(C) EFFECT OF THICKNESS OF SHAVING ON CUTTING SPEED THE MOST IMPORTANT SUBJECT FOR EXPERIMENT
291 It is the THICKNESS OF SHAVING, then (item C in the list above) which must be first considered, as this element has more effect upon the design of our standard tools, and in fact upon the whole problem of cutting metals than any other single item which is completely under the control of those who are managing a shop.
EXPERIMENTS SHOWING EFFECT UPON CUTTING SPEED OF VARYING THE THICKNESS OF THE SHAVING, A TOOL WITH STRAIGHT- EDGE BEING USED, REMOVING A SHAVING IN ALL CASES EXACTLY ONE INCH LONG
292 The following experiments were made to determine the effect upon the cutting speed of varying the thickness of the shaving. For this purpose a number of broad nosed tools with straight cutting edges, similar to that shown in Folder 7, Fig. 35, were forged from ordinary tempered carbon tool steel. Straight cutting edges were used in order that the shaving should be of the same thickness throughout. The corner of the tool, however, which cuts at the smaller of the two diameters of the forging was rounded to a radius of exactly 1/8 of an inch. This was necessary in order to thin the shaving down sufficiently at this point to absolutely insure that part of the tool which gives the required smoothness to the forging from giving out before the tool dulls along the straight line of the cutting edge.
293 In these experiments the tool was set in the lathe as shown in Folder 16, Fig. 111, so that exactly one inch of the STRAIGHT PORTION of the cutting edge was at all times under pressure of the shaving. In all cases a feed of 8/100 of an inch was used, so that the thickness of the shaving was in each case directly proportional to the depth of the cut.
294 These experiments were made upon a forging of the following chemical composition:
Carbon . . . . . . - - . . . . . . . . . . . . . . . . . . . . . . . .0.369 per cent
Manganese . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.517 per cent
Silicon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.238 per cent
Phosphorus . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.043 per cent
Sulphur . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.051 per cent
Tensile test bars actually cut from the body of the forging showed the following physical properties:
Tensile strength . . . . . . . . . . . . . . . . . . . . . . . . . .82,947 lbs.
Stretch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21.50 per cent
Contraction of area . . . . . . . . . . . . . . . . . . . . . . . .30.00 per cent
295 A heavy stream of water was thrown throughout the experiments upon the shaving just at the spot at which it was being removed from the forging by the tool.
296 Depths of cut of exactly 1/8, 3/16, 1/4 and 3/8 inch were used, corresponding to thicknesses of shaving of 0.01, 0.015, 0.02 and 0.03 inch.
297 The speeds corresponding to these cuts, each of which was of 20 minutes’ duration, are given in Folder 16, Table 113. These cutting speeds are plotted on Folder 16, Figs. 114 and 115, and a curve corresponding to the following formula is drawn approximately through these various points. They are also plotted on logarithmic paper, on Folder 16, Fig. 113, on which the speed points lie approximately in a straight line.
V = 1.54/(t^(2/3))
in which
V = cutting speed in feet per minute for 20-minute cut;
t = thickness of shaving in inches.
298 On Folder 16, Table 113, will be seen also the ratio between the cutting speeds of each of these thicknesses of shaving, from which it will be noted, for example, that by dividing the thickness of the shaving by 3, the cutting speed is increased in the ratio of 1 to 1.8. For further description of these experiments, see paragraph 761.
Updated 16 July 2021
Pub 30.6.2020
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