Table 1. Typical recommendations and strength expectations for spot welding.

Resistance spotwelding parameters for low carbon and stainless steels and aluminum.
These are general average values, not to be used for strength calculation purposes
expected shear strength in lbs./spot (kg. /spot)
thinnest material thickness recommended electrode contact diameter f used zone diameter expected recommended flange overlap (minimum) recommended single-spot weld spacing aluminum alloy 5052-H34 carbon steel 70KSI stainless steel 90KSI
in.

0.010
0.021
0.031
0.040
0.050
0.062
0.078
0.094
0.109
0.125
0.180

 mm

0.25
0.53
0.79
1.02
1.27
1.57
1.98
2.39
2.77
3.18
4.57

 in.

0.13
0.19
0.19
0.25
0.25
0.25
0.31
0.3
0.31
0.38
0.38

 mm

3.0
5.0
5.0
6.5
6.5
6.5
8.0
8.0
8.0
10.0
10.0

 in.

0.10
0.13
0.16
0.19
0.22
0.25
0.29
0.31
0.32
0.33
0.35

 mm

2.5
3.0
4.0
5.0
5.5
6.5
7.5
8.0
8.0
8.5
9.0

 in.

0.38
0.44
0 44
0.50
0.56
0.63
0.69
0.75
0.81
0.88
1.0

 mm

10.0
11.0
11.0
13.0
14.0
16.0
17.5
19.0
20.5
22.5
25.0

 in.

0.75
0.75
1.0
1.0
1.0
1.2
1 5
1.8
2.2
2.5
2.5

 mm

19
19
25
25
25
31
38
46
56
64
64

 Ibs.

154
264
528
748
1122
1584
2068
2596
3036
3564
3784

 kg.

70
120
240
340
510
720
940
1180
1380
1620
1720

 Ibs.

286
704
1254
2024
2970
4070
5940
7590
9130
11000
11660

 kg.

130
320
570
920
1350
1850
2700
3450
4150
5000
5300

 Ibs.

374
1034
1760
2794
3740
5280
7480
9240
11000
13200
14520

 kg.

170
470
800
1270
1700
2400
3400
4200
5000
6000
6600
note: one half or less spotweld spacing as given in above table can be achieved by the use of multi-point electrodes.
The same can be accomplished with a single spot electrode on a dual circuit welder. There, a higher current is used for all subsequent spots to overcome the shunting effect.
Frequent destructive testing is indicated in these cases to maintain correct settings and quality control. Check with your weldment supplier for applicability and associated cost.
Go back to Spot Welding Chapter