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Show TH 5 PRINCIPLE O SCIENTIFI MANAGEMEN proportion is as 1 in the case of semi-hardened steel or chilled iro The meanin to 100 in the case of a very soft, low-carbon steel. of this quotation is that soft steel can be cut 100 times as fast a the hard steel or chilled iron. The ratios which are given, then after each of these elements, indicate the wide range of judgmen which practically every machinist. has been called upon to exercis in the past in determining the best speed at which to run th machine and the best feed to use (A) The quality of the metal which is to be cut, 7.e., its hardnes or other qualities which affect the cutting speed The proportio is as 1 in the case of semi-hardened steel or chilled iron to 100 i the case of very soft, low-carbon steel (B) The chemical composition of the steel from which the too is made, and the heat treatment of the tool The proportion is a 1 in tools made from tempered carbon steel to 7 in the best high-spee tools (C The thickness of the shaving, or, the thickness of the spira strip or band of metal which is to be removed by the tool proportion is as 1 with thickness of shaving 1% of an inch to 3% wit thickness of shavin Th &5 of an inch (D) The shape or contour of th proportion is as 1 in a thread tool t (E) Whethera copious stream o is used on the tool. The proportio cutting edge of the tool Th 6 in a broad-nosed cutting tool water or other cooling mediu is as 1 for tool running dry t 1.41 for tool cooled by a copious stream of water (F) The depth of the cut. The proportion is as 1 with }-inc depth of cut to 1.36 with % inch dept (G) The duration of the cut, 7.e., th under pressure of the shaving withou portion is as 1 when tool is to be groun tool is to be ground every 20 minutes of cut time which a tool must las being reground The proevery 1% hours to 1.20 whe (H) The lip and clearance angles of the tool. The proportion i as 1 with lip angle of 68 degrees to 1.023 with lip angle of 61 degrees (J) The elasticity of the work and of the tool on account of producing chatter The proportion is as 1 with tool chattering to 1.1 with tool running smoothly (K) The diameter of the casting or forging which is being cut (L The pressure of the chip or shaving upon the cutting surfac of the tool M) The pulling power and the speed and feed changes of th machine It may seem preposterous to many people that it should hav |
