Preparation

e. Punch each welding point where necessary to make a centering point for the drill bit.
Tools required:

• Hammer
• Graver.

WARNING:
Centre punching of each welding point should be deep and exactly centered. An off-centre punch will not permit the welding point to be completely removed while a weak punch will not allow the drill bit to be securely guided.

f. Remove the spot welds using a chamfering machine or pneumatic drill.
Tools required:

• Spot-cutter
• Drill

NOTE:
Where it is not possible to use a spot-cutter or drill, use a chisel.
The chisel is particularly useful for spot-cutting thin sheet metal from thick sheet metal.

WARNING:
Use gloves and protective glasses.

WARNING:

• Position the chamfering machine over the centre of the spot to be removed.
• To facilitate the operation a cutting speed of approximately 1000 r.p.m. should be used.
• Adjust the milling depth by acting on the screw.
• Care should be taken to avoid drilling mating components. Plug any holes by welding.
• Holes can reduce component rigidity and give rise to water seepage.

g. Remove the traces of welding using a chisel.
Tools required:

• Chisel
• Hammer.

PREPARATION

a. Grind the metal sheet at the welding points using a sander.
Tools required:

• Grinding machine with brush
• Disk- sander.

WARNING

• When using the sander care should be taken to avoid excessively reducing the thickness of the metal sheet as this may adversely affect welding strength.
• Thoroughly clean the metal dust from the ground surfaces and surrounding areas.
• Metal dust reduces welding stetal dust from the ground surfaces and surrounding areas.
• Metal dust reduces welding strength and can lead to corrosion.

b. Straighten the buckled areas with a hammer and dolly block.
Tools required:

• Hammer
• Dolly block.