The worn area would need to be machined smooth, and a repair sleeve fitted to bring the diameter back to slightly over the original specification, then ground and polished to a smooth enough surface for the bearing rollers to ride on. Remember that the bearing also supports the weight if the truck, so the metallurgy of both the axle and the bearing must be compatible.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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