Page 173 - The Tribology Handbook

Gears B3

CHOICE OF MATERIALS

Table 3.2 A//owable stresses on materials for spur, helical, straight bevel, spiral bevel and
hypoid bevel gears

PB I 5 50 50 70 185 - - - 1400PB2 Sand cast
PB2 6 60 60 85 230 - - - 1400PB2 1 Chill cast
1400PB2
PB3 7 70 70 90 260 - - - centrifugal
cast
M1 6 76 76 140 310 - I - 309W24/8 Malleable iron
GI 7 40 40 165-190 185 I - - 1452 Ord. grade
C2 9 52 52 210-220 245 - - - 1452 grade
c3 IO 70 70 220-230 340 - - - 1452 High grade
c5 IO it0 110 145-170 540 280 - - 592 Steel as cast
~~
BS 970
f 10.5 145 145 15@-180 540-4518 280 f - 080A35 Normalised
2 12.5 160 I60 180-230 61G740 430 - - 150M28 Q
3 16..5 172.5 172.5 200-250 695-850 355 - - - Normalised
4 18.5 186 186 220-270 74@-895 585 c - 708M40 S
5 18.5 1 86 186 220-270 740-895 585 - - 81711140 S
-
6 21.5 215 215 250-300 850-1000 680 - - 830M31 T
7 26.0 235 235 290-340 970-1190 770 - 830M31 V
8 45.0 110 145 150-180 540-6 18 450 1390 080A35
9 45.0 165 145 150-180 54&6 18 450 1390 080A35
IO 45.0 130 172 20P250 695-850 450 1390 708M40
I1 45.0 195 I72 200-250 695-850 450 1390 708M40
12 45.0 145 186 220-270 740-895 450 1390 817M40
13 45.0 207 1 86 220-270 740-895 450 1390 817M40
14 45.0 240 215 250-300 850-1000 450 1390 826M3 1
15 45.0 172 227 270-320 925-1005 450 I390 826M40
16 45.0 255 227 270-320 925-1 005 450 1390 826M40
17 55.0 130 172 206250 695-850 - 710 1850 722M24 R. Nitrided
18 62.0 145 186 223-270 740495 - 710 1850 722M24 S. Nitrided
I9 69 0 207 276 375444 1205-1390 - 710 1850 897M39 Nitrided

20 69.0 255* 172 21&240 695-772 - 710 t%5O 665M17
21 76 0 282* 214 25&300 740-1005 - 710
22 83 0 345, 262 350-410 1160-1312 - 710 1850 659Ml5
__ - ~-
Where: Notes:
Sco = allowable contact stress 1. Materials 8 to 22, the basic allowable bending stress (S~O),
=
3~0~9 allowable skin bending stress used in estimating load capacity of gears depends on the
SBOC = allowable core bending stress ratio of the depth of the hard skin at the root fillets to the
CK: Cast iron MI: Malleable iron normal pitch (circular pitch) of the teeth
CS: Cast steel PB: Phosphor bronze
BHN: Brinell hardness number SBOC
VHN: Vichers hardness number SRO = sR#S Or [l-7.5 (depth of skin)/normal pitch]
*MuItiply by t.8 for very smooth fillets not ground after
hardening. whichever is the less.
2. Materials 8 to 22, values of Sco are reliable only for skin
(FH)?: Hardening by flame or induction over the whole thicker than.
working surfaces of the tooth flanks but excludes the
fillets - applies to modules larger than 3.5. 0.003 d X D (d + D)
(CH)t Hardeaing by name or induction over the whole tooth 3. Materials I to 8, the value of Seo is approx:
flanks, fillets and connecting root surfaces - applies to
modules between 5 and 28. Ult. Tensile3
Spin hardening - appties to modules between 3.5 and SBO = 600 X Ult Tensife -
2.0. 60
4. Gear cutting becomes difficuit if BHN exceeds 270.

83.3