Machinery's Handbook, 31st Edition
Machining Power
1151
E K CQW p
K CW P E p m
. 232 092 130 75 080 . × × × . . .
Q
=
=
=
P
c
m
m
max
3
= = =
. 216 60
cm
/
sec
V fd Q
. 045 32 60 216 . . × ×
max
=
Q V fd = k
a
60
900
. / m
min
The calculated cutting speed of 90.0 m/min is correct, but too low for carbide cutting tools. Thirty years ago, recommended cutting speed for turning AISI 1050 steel, 200– 210 BHN, depth of cut 4.0 mm, was 160 m/min. Currently, using advanced coated carbide inserts, the cutting speed is increased up to 300 m/min for the depth of cut of 2.5–5.0 mm and a 0.38 mm/rev feed rate. Estimating Drilling Thrust, Torque, and Power.— Although the lips of a drill cut metal and produce a chip in the same manner as the cutting edges of other metal cutting tools, the chisel edge removes the metal by means of a very complex combination of extru- sion and cutting. For this reason a separate method must be used to estimate the power required for drilling. Also, it is often desirable to know the magnitude of the thrust and the torque required to drill a hole. The formulas and tabular data provided in this section are based on information supplied by the National Twist Drill Division of Regal-Beloit Corp. The values in Table 6 through Table 9 are for sharp drills and the tool wear factors are given in Table 3. For most ordinary drilling operations 1.30 can be used as the tool wear factor. When drilling most difficult-to-machine materials and when the drill is al - lowed to become very dull, 1.50 should be used as the value of this factor. It is usually more convenient to measure the web thickness at the drill point than the length of the chisel edge; for this reason, the approximate w / d ratio corresponding to each c / d ratio for a correctly ground drill is provided in Table 7. For most standard twist drills the c / d ratio is 0.18, unless the drill has been ground short or the web has been thinned. The c / d ratio of split-point drills is 0.03. The formulas given below can be used for spade drills, as well as for twist drills. Separate formulas are required for use with customary inch units and for SI metric units. Table 6. Work Material Factor, K d , for Drilling with a Sharp Drill
Material Constant, K d
Material Constant, K d
Work Material
Work Material
Austenitic Stainless Steel (Type 316)
AISI 1117 (Resulfurized free machining mild steel) 12,000
24,000
a for Torque
18,000 a for Torque 29,000 a for Thrust
Steel, 200 BHN Steel, 300 BHN Steel, 400 BHN Cast Iron, 150 BHN Most Aluminum Alloys Most Magnesium Alloys
24,000 Titanium Alloy Ti6Al4V 40R c 31,000 34,000 René 41 40R c
40,000
ab min.
14,000
30,000 a for Torque 37,000 a for Thrust
7,000 Hastelloy-C
4,000 14,000
Most Brasses Leaded Brass
7,000 a Values based upon a limited number of tests. b Will increase with rapid wear.
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