Page 270 - Analysis and Design of Machine Elements

Table 9.2 Basic allowable stresses of wormgears [4, 6].
Allowable contact Allowable bending
Wormgear Materials Casting stresses at stresses at
′
′
6
7
materials designation methods N = 10 [ H ] ,MPa N = 10 [ F ] ,MPa
Sliding
velocity
ASTM/ limits v s , Worm surface One side Both sides
−1
AISI No. BS No. DIN No. GB No. ISO No (m s ) hardness meshing meshing
≤45 HRC >45 HRC
Cast tin C90700 PB4 ZCuSn CuSn10P Sand mould 160 180 45 30
bronze 10P1 (v s ≤ 12)
Metal mould 220 240 63 40
(v s ≤ 25)
Cast lead C83600 LG2 G-CuSn5 ZCuSn5 CuPb5 Sand mould 110 130 30 22
bronze ZnPb Pb5Zn5 Sn5Zn5 (v s ≤ 10)
Metal mould 130 145 32 26
(v s ≤ 12)
Cast C95200 AB1 G-CuAl ZCuAl CuAl Sand mould SeeFigure9.7 80 60
aluminium 10Fe 10Fe3 10Fe3 (v s ≤ 10)
iron bronze
Metal mould 90 70
(v s ≤ 10)
Grey cast No. 25 EN-GJL- GG15 HT150 150 Sand mould 40 28
iron 150 (v s ≤ 2)
No. 35 EN-GJL- GG25 HT250 250 Sand mould 48 34
No. 40 250 (v s ≤ 2–5)