Repairs and rebuilding
Repair is the one job in this section that is brought in rather than ordered. It usually arrives after somebody else has already tried, so half the work is removing the previous weld.
Six techniques
- Crack — stop-drill the ends, prepare the edges, weld it up. Without stop-drilling the crack runs on past the weld.
- Insert instead of a cut-out — when the metal has burnt away or rusted through and there is nothing left to weld to.
- Surface hardfacing — bucket, blade, auger: the size is brought back with weld metal and the excess machined off.
- Cast iron — nickel electrode, studs, short scattered runs, slow cooling.
- Aluminium — strip the oxide, weld TIG on AC.
- Bearing seat on a shaft — hardface and turn back to the bearing size.
Trailers and machinery
A separate and very frequent group of jobs: frames, drawbars, blades and everything that breaks on attachments. Here repair almost always beats replacement, because the assembly is large and the damage local.
A dropside trailer is built for papers and registration — meaning the dimensions, the coupling and the lighting have to satisfy the requirements rather than convenience. A blade or a linkage for a tiller or a quad carries no such constraint and is made to suit.
When repair makes no sense
Three cases where it is more honest to decline:
- The part works under pressure or in lifting gear and nobody knows its loading history.
- The crack runs through a zone that has already been welded twice: the metal there is overheated and brittle.
- Dismantling and downtime cost more than a new part — a sum to do before, not after.
Where to go next
The metallurgy is covered separately: welding cast iron for nickel electrodes and parameters, welding aluminium for the oxide and alternating current, and cracks in welds for why they appear in the first place. Items made new rather than repaired are in shop products.
Frequently asked questions
Why is a crack drilled first?
Because a crack has a sharp tip and stress concentrates in it. Welded up without stop-drilling, it carries on growing past the weld — out of the same tip, still in the metal. A 3–4 mm hole at each end removes the concentrator.
Is repair always cheaper than a new part?
No. The sum has to include dismantling, transport and downtime. Repair wins where the part is large, rare or out of production; on a cheap series part the dismantling alone often costs more than replacement.
What do you weld cast iron with?
Nickel electrodes, short scattered runs, peened and never overheated. Studs are often added: they hold the weld mechanically rather than by adhesion alone. Cast iron dislikes rapid heating and dislikes rapid cooling even more.
Why is aluminium welded on AC?
Because of the oxide film. Aluminium oxide melts at around 2050 °C, the metal itself at 660 °C. Alternating current in TIG breaks the film up on the positive half-cycle, and only because of that does a weld form at all.
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