Machinery's Handbook, 31st Edition
1146
Machining Power Table 1a. Power Constants K p Using Sharp Cutting Tools Table 1a. (Continued) Power Constants K p Using Sharp Cutting Tools
Brinell Hardness Number
Brinell Hardness Number
K p Metric Units
K p Metric Units
K p Inch Units
K p Inch Units
Material
Material
High-Temperature Alloys, Tool Steel, Stainless Steel, and Nonferrous Metals
High-Temperature Alloys
150-175 0.60 1.64 175-200 0.72 1.97 200-250 0.88 2.40 … 0.25 0.68 … 0.91 2.48 … 0.83 2.27 … 0.50 1.36 … 0.25 0.68 … 0.30 0.82
A286 A286
165 0.82 2.24 285 0.93 2.54
Stainless Steel
Chromoloy Chromoloy Inco 700 Inco 702
200 0.78 3.22 Zinc Die-Cast Alloys 310 1.18 3.00 Copper (pure)
330 1.12 3.06 Brass 230 1.103.00 Hard 230 1.103.00 Soft 310 1.203.28 Leaded 375 1.10 3.00 Bronze Hard 340 0.65 1.77
Hastelloy-B 230 1.103.00 Medium
M-252 M-252 Ti-150A U-500
… 0.91 2.48 … 0.50 1.36
Monel Metal
… 1.002.73 Medium 175-200 0.75 2.05 Aluminum 200-2500.882.40 Cast 250-300 0.98 2.68 Rolled (hard) 300-350 1.20 3.28 350-400 1.30 3.55 Magnesium Alloys
… 0.25 0.68 … 0.33 0.90
Tool Steel
… 0.10 0.27
The value of the power constant is essentially unaffected by the cutting speed, the depth of cut, and the cutting tool material. Factors that do affect the value of the power constant, and thereby the power required to cut a material, include the hardness and microstructure of the work material, the feed rate, the rake angle of the cutting tool, and whether the cutting edge of the tool is sharp or dull. Values are given in the power constant tables for different material hardness levels, whenever this information is available. Feed factors for the power constant are given in Table 2. All metal cutting tools wear but a worn cutting edge requires more power to cut than a sharp cutting edge. Factors to provide for tool wear are given in Table 3. In this table, the extra-heavy-duty category for milling and turning occurs only on operations where the tool is allowed to wear more than a normal amount before it is replaced, such as roll turning. The effect of the rake angle usually can be disregarded. The rake angle for which most of the data in the power constant tables are given is positive 14 degrees. Only when the deviation from this angle is large is it necessary to make an adjustment. Using a rake angle that is more positive reduces the power required approximately 1 percent per degree; using a rake angle that is more negative increases the power required; again approximately 1 percent per degree. Many indexable insert cutting tools are formed with an integral chip breaker or other cutting edge modifications, which have the effect of reducing the power required to cut a material. The extent of this effect cannot be predicted without a test of each design. Cutting fluids will also usually reduce the power required, when operating in the lower range of cutting speeds. Again, the extent of this effect cannot be predicted because each cutting fluid exhibits its own characteristics.
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