Hi,
My neighbor recently gave me a disassembled 40hp engine that I'd like to rebuild. Over the years while in storage it's developed a rust spot (approx.
2mm in dia.) on one of the cramk journals. Tha crank has never been ground and the rest of the journals look fine, very little wear. Is there a way to deal with this or must I regrind the crank ?TIA for any help/advice,
Len
A good machine shop could answer that question, though you may want to grind to assure proper surface area.
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The answer depends on the rust. And on the dimensions of the other journals.
If the rust were just 'haze' -- the sort of thing that can be wiped away with a cloth -- then the surface may not be etched and might be returned to service after polishing. But rust tends to etch craters into the surface of the metal and usually dictates regrinding to the next under-size (less a few tenths), heat-treating the reground surface (ie, 'nitriding' ) then polishing.
A good journal is mirror-bright -- literally; you can see your face in the polished surface. Anything less is... something lesser; shade-tree stuff sold to kiddies. Indeed, a lot of reground crankshafts intended for the Kiddie Trade are not hardened.
(Original VW crankshafts are just mild steel, their DIN-spec'd alloy very similar to SAE 1045 -- very good stuff for forging but not especially strong and must be nitrided or surface-hardened when used as a crankshaft.)
-Bob Hoover
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