Workshop Technology
Spot welding is used for welding

Lap joints in plates having 0.025 mm to 1.25 mm thickness
Lap joints in plates having thickness above 3 mm
Butt joints in plates having thickness above 3 mm
Butt joints in plates having 0.025 mm to 1.25 mm thickness

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Workshop Technology
For arc welding

Direct current is used
Alternating current with high frequency is used
Any one of these
Alternating current with low frequency is used

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Workshop Technology
Piercing is an operation of cutting

A flat sheet to the desired shape
A hole (other than cylindrical) in a sheet of metal by the punch and the die
A cylindrical hole in a sheet of metal by the punch and the die
A number of holes evenly spaced in a regular pattern on a sheet of metal

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