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TABLE 3
TABLE OF COMBINED LOADING OF SHAFTS
(Based on #303 stainless Steel With Smax = 12,000 psi. end Minor Shocks)

Shaft
Dia.		 Moment Inch-Pounds
1/16 Tortion
Bending		 0
0.396		 0.040
0.394		 0.079
0.388		 0.119
0.378		 0.159
0.362		 0.198
0.342		 0.238
0.317		 0.277
0.283		 0.317
0.236		 0.356
0.173		 0.396
0
3/32 Tortion
Bending		 0
1.34		 0.134
1.33		 0.268
1.31		 0.402
1.28		 0.536
1.23		 0.670
1.16		 0.804
1.07		 0.938
0.953		 1.07
0.803		 1.21
0.572		 1.34
0
1/8 Tortion
Bending		 0
3.25		 0.325
3.24		 0.650
3.20		 0.975
3.09		 1.30
2.98		 1.63
2.86		 1.95
2.60		 2.28
2.31		 2.60
1.95		 2.92
1.43		 3.25
0
5/32 Tortion
Bending		 0
6.32		 0.632
6.28		 1.26
6.18		 1.89
6.02		 2.52
5.79		 3.16
5.47		 3.79
5.06		 4.42
4.51		 5.05
3.78		 5.68
2.76		 6.32
0
3/16 Tortion
Bending		 0
11.1		 1.11
10.9		 2.22
10.8		 3.33
10.5		 4.44
10.3		 5.55
9.56		 6.66
8.82		 7.77
7.86		 8.88
6.58		 9.99
4.73		 11.1
0
7/32 Tortion
Bending		 0
17.2		 1.72
17.1		 3.44
16.8		 5.16
16.5		 6.88
15.8		 8.60
14.8		 10.3
13.8		 12.0
12.7		 13.8
10.7		 15.5
7.53		 17.2
0
1/4 Tortion
Bending		 0
26.0		 2.60
25.8		 5.20
25.4		 7.80
24.8		 10.4
23.8		 13.0
22.5		 15.6
20.8		 18.2
18.5		 20.8
15.6		 23.4
11.3		 26.0
0
5/16 Tortion
Bending		 0
50.5		 5.06
50.3		 10.1
49.6		 15.2
48.2		 20.2
46.3		 25.2
43.7		 30.3
40.4		 35.4
36.1		 40.4
30.4		 45.5
2.19		 50.5
0
3/8 Tortion
Bending		 0
87.7		 8.77
87.4		 17.5
85.9		 26.3
83.7		 35.1
80.4		 43.8
75.9		 52.6
70.2		 61.4
62.6		 70.2
52.6		 78.9
38.4		 87.7
0
1/2 Tortion
Bending		 0
208		 20.6
207.4		 41.6
205		 62.4
200		 83.2
192		 104
181		 124.8
168		 145.6
151		 166.4
127.5		 187.2
93.5		 208.0
0
5/8 Tortion
Bending		 0
406.2		 40.6
404.2		 81.2
398		 121.8
387.5		 162.4
372.3		 203.0
351.9		 243.6
325.1		 284.2
290.2		 324.8
244.0		 365.4
177.5		 406.2
0
3/4 Tortion
Bending		 0
702		 70.2
698.4		 140.4
687.8		 210.6
669.6		 280.8
643.3		 351.0
607.9		 421.2
561.5		 491.4
501.3		 561.6
421.1		 631.8
305.9		 702
0

If AISI 1213 steel is used, Smax = 8000 psi. and the diameters given in the tables have to be increased by 15%.

Example
A 1/50th H.P. motor drives a shaft rotating at 315 RPM and is subject to a bending moment of 6 in-lbs, the load application being sudden. Determine shaft size for a #303 stainless steel shaft.
    From equation  (1),

    T  =    63,025 (H.P.)   =  ( 63,025) (0.02 )  = 4 in-lbs.
                      N                         (315)

Referring to Table 3 (Combined Loading), we find that the combination of an allowable torsional moment in excess of 4 in-lbs. (actual 4.44) together with an allowable bending moment in excess of 6 in-lbs. (actual 10.3) first occurs for a 3/16" shaft diameter.
If there were no bending moment and the load were to be applied gradually (Km = Kt = 1) Table 1 shows that a 1/8” shaft diameter would be sufficient.

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