Broaches and Broaching Table 1. Designing Data for Surface Broaches Machinery's Handbook, 31st Edition
1046
Depth of Cut per Tooth
Face Angle or Rake, Degrees
Clearance Angle, Degrees Rough Finish
Finishing
Roughing a
inch
mm
inch
mm
Material to be Broached Steel, High Tensile Strength Steel, Med.Tensile Strength
0.0015–0.002 0.04–0.05 0.0005 0.013 10–12 1.5–3 0.5–1 0.0025–0.005 0.06–0.13 0.0005 0.013 14–18 1.5–3 0.5–1
0.0025–0.005 0.06–0.13 0.0005 0.013 0.0025–0.005 0.06–0.13 0.0005 0.013 0.003–0.005 0.08–0.13 0.0005 0.013 0.005–0.010 0.13–0.25 0.0010 0.025 0.010–0.025 0.25–0.64 0.0005 0.013 0.005–0.010 0.13–0.25 0.0010 0.025 0.005–0.010 0.13–0.25 0.0010 0.025 0.010–0.015 0.25–0.38 0.0010 0.025
10
1.53 1.5–3
0.5 0.5 0.5 0.5
Cast Steel
Malleable Iron Cast Iron, Soft Cast Iron, Hard Zinc Die Castings
7
0.006–0.010 0.15–0.25 0.0005 0.013 10–15 1.5–3
5
1.5–3
12 b
5 0 3 3
2 0 1 1
Cast Bronze
8
15 b 12 b 20 b
Wrought Aluminum Alloys Cast Aluminum Alloys Magnesium Die Castings
3 1 a The lower depth-of-cut values for roughing are recommended when work is not very rigid, the tolerance is small, a good finish is required, or length of cut is comparatively short. b In broaching these materials, smooth surfaces for tooth and chip spaces are especially recommended. Table 2. Broaching Pressure P for Use in Pitch Formulas (2a) and (2b)
Depth d of cut per tooth, inch (mm) Side-cutting Broaches 0.024 (0.60) 0.01 (0.25) 0.004 (0.10) 0.002 (0.05) 0.001 (0.025) Pressure, P Pressure, P Cut, d
Material to be Broached Steel, High Tensile Strength Steel, Med. Tensile Strength
inch mm
250 3447 312 4302 200 2758 0.004 0.10 158 2179 185 2551 243 3351 143 1972 0.006 0.15
… … … …
… … … …
Cast Steel
128 1765 158 2179 108 1489 128 1765
115 1586 0.006 0.15 100 1379 0.006 0.15 115 1586 0.020 0.51
… … … …
… …
Malleable Iron
… … … …
… …
Cast Iron Cast Brass
115 1586 115 1586 143 1972
… …
… …
50 689 50 689 85 1172 85 1172 70 965 70 965
… …
… … … … … … … …
Brass, Hot-pressed Zinc Die Castings Wrought Aluminum Cast Aluminum Magnesium Alloy Cast Bronze
… …
… … … … … … … …
… …
… … … … … … … …
35 483 35 483
…………… ……………
70 965 70 965 85 1172 85 1172
… …
… … … … … … … …
… …
… … … … … … … …
35 483 35 483
…………… ……………
The minimum pitch shown by Formula (1) is based upon the receiving capacity of the chip space. The minimum pitch should not be less than 0.2 inch (5.0 mm) unless a smaller pitch is required for extremely short cuts to provide at least two teeth in contact simultaneously with the part being broached. A reduction below 0.2 inch (5.0 mm) is seldom required in surface broaching but may be necessary in connection with internal broaching. (1) Whether the minimum pitch may be used or not depends upon the power of the available machine. The factor F in the formula provides for the increase in volume as the material is broached into chips. If a broach has adjustable inserts for the finishing teeth, the pitch of the finishing teeth may be smaller than the pitch of the roughing teeth because of the smaller depth d of the cut. The higher value of F for finishing teeth prevents the pitch from becoming too small, so that the spirally curled chips will not be crowded into too small a Minimum pitch 3 LdF =
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