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Source: Spot Weld, Inc. set-up guide for low-carbon steel, hot rolled, pickled and lightly oiled (SAE 1005–SAE 1010), ultimate strength 42,000–45,000 PSI.
This table gives optimum welding schedules for single-impulse spot welding. Three quality classes are provided: Class A (Best Quality) uses higher current and force for the most consistent nugget; Class B (Medium Quality) is a balanced setting; Class C (Good Quality) uses the minimum acceptable parameters. All times are in 60 Hz cycles.
Optimum Conditions — Spot Welding Schedules
| Sheet Thickness (in.) |
Electrode (All Classes) |
Min. Weld Spacing (Note 4) (in.) |
Min. Contacting Overlap (Note 6) (in.) |
Class A — Best Quality | Class B — Medium Quality | Class C — Good Quality | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
Electrode Diam. & Shape  Min. D / Max. d (in.) |
Weld Time (Note 7) (cycles) |
Electrode Force (lbs) |
Welding Current (amps) |
Diam. of Fused Zone  Dw (in.) |
Avg. Tensile Shear Strength (±14%) (lbs) |
Weld Time (Note 7) (cycles) |
Electrode Force (lbs) |
Welding Current (amps) |
Diam. of Fused Zone Dw (in.) |
Avg. Tensile Shear Strength (±17%) (lbs) |
Weld Time (Note 7) (cycles) |
Electrode Force (lbs) |
Welding Current (amps) |
Diam. of Fused Zone Dw (in.) |
Avg. Tensile Shear Strength (±20%) (lbs) |
||||
| .010 | 1/2 | 1/8 | 1/4 | 3/8 | 4 | 200 | 4,000 | .13 | 235 | 5 | 130 | 3,700 | .12 | 200 | 15 | 65 | 3,000 | .11 | 160 |
| .021 | 1/2 | 3/16 | 3/8 | 7/16 | 6 | 300 | 6,100 | .17 | 530 | 10 | 200 | 5,100 | .16 | 460 | 22 | 100 | 3,800 | .14 | 390 |
| .031 | 1/2 | 3/16 | 1/2 | 7/16 | 8 | 400 | 8,000 | .21 | 980 | 15 | 275 | 6,300 | .20 | 850 | 29 | 135 | 4,700 | .18 | 790 |
| .040 | 5/8 | 1/4 | 3/4 | 1/2 | 10 | 500 | 9,200 | .23 | 1,305 | 21 | 360 | 7,500 | .22 | 1,230 | 38 | 180 | 5,600 | .21 | 1,180 |
| .050 | 5/8 | 1/4 | 7/8 | 9/16 | 12 | 650 | 10,300 | .25 | 1,820 | 24 | 410 | 8,000 | .23 | 1,700 | 42 | 205 | 6,100 | .22 | 1,600 |
| .062 | 5/8 | 1/4 | 1 | 5/8 | 14 | 800 | 11,600 | .27 | 2,350 | 29 | 500 | 9,000 | .26 | 2,150 | 48 | 250 | 6,800 | .25 | 2,050 |
| .078 | 5/8 | 5/16 | 1-1/8 | 11/16 | 21 | 1,100 | 13,300 | .31 | 3,225 | 36 | 650 | 10,400 | .30 | 3,025 | 58 | 325 | 7,900 | .28 | 2,900 |
| .094 | 5/8 | 5/16 | 1-1/4 | 3/4 | 25 | 1,300 | 14,700 | .34 | 4,100 | 44 | 790 | 11,400 | .33 | 3,900 | 66 | 390 | 8,800 | .31 | 3,750 |
| .109 | 7/8 | 3/8 | 1-5/16 | 13/16 | 29 | 1,600 | 16,100 | .37 | 5,300 | 50 | 960 | 12,200 | .36 | 5,050 | 72 | 480 | 9,500 | .35 | 4,850 |
| .125 | 7/8 | 3/8 | 1-1/2 | 7/8 | 30 | 1,800 | 17,500 | .40 | 6,900 | 60 | 1,140 | 12,900 | .39 | 6,500 | 78 | 570 | 10,000 | .37 | 6,150 |
| .156 | 7/8 | 1/2 | 1‑3/4 | 1 | 93 | 2,500 | 18,000 | .446 | 6,500 | 93 | 2,500 | 18,000 | .446 | 6,500 | 93 | 2,500 | 18,000 | .446 | 6,500 |
| .187 | 1 | 5/8 | 2 | 1‑1/2 | 130 | 3,340 | 20,500 | .516 | 9,000 | 130 | 3,340 | 20,500 | .516 | 9,000 | 130 | 3,340 | 20,500 | .516 | 9,000 |
| .250 | 1‑1/4 | 3/4 | 4 | 1‑1/2 | 230 | 5,560 | 26,000 | .660 | 18,000 | 230 | 5,560 | 26,000 | .660 | 18,000 | 230 | 5,560 | 26,000 | .660 | 18,000 |
Notes
Note numbers match the original source document.
- Low-carbon steel as hot rolled, pickled, and slightly oiled, ultimate strength 42,000–45,000 PSI. Similar to SAE 1005–SAE 1010.
- Electrode material is CMW 3.
- Surface of steel is lightly oiled but free from grease, scale, or dirt.
- Min. Weld Spacing: The minimum distance between weld centers at which no increase in welding current is necessary to compensate for the shunted current effect in adjacent welds.
- Radius face electrodes may be used: 0.010–0.031 in. → 2″ radius; 0.031–0.078 in. → 3″ radius; 0.078–0.125 in. → 4″ radius.
- Min. Contacting Overlap: The minimum overlap dimension between the two workpieces required to achieve the specified weld nugget without edge cracking or expulsion.
- Weld Time: Indicated in cycles of 60 Hz frequency (1 cycle = 1/60 second ≈ 16.7 ms).
- Tensile shear strength values are based on recommended test sample sizes (per AWS standards). Tolerances: Class A ±14%, Class B ±17%, Class C ±20%.
- Tolerance for machining of electrode diameter “d” is ±0.015″ of specified dimension.
- Electrode force does not include force required to press ill-fitting parts together.
- Permissible Schedule Variations (rows highlighted in yellow): Data for sheet thickness 0.156″–0.250″ is sourced from the Permissible Schedule Variations table in the original Spot Weld, Inc. source document. These represent a single recommended schedule (not differentiated by quality class). Hold times: 0.156″ = 50 cycles; 0.187″ = 55 cycles; 0.250″ = 60 cycles.
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