Originally Posted by onehundred80
Rasim
Crankshafts have hardened wear surfaces and the inner core of the material is much softer but stronger. If the crankshaft was hard all the way through it would soon snap into pieces.
I do not know the specific depth of the hardened surface on these crankshafts, normally it is only a fraction of a millimeter.
If Mercedes does not offer bearings for a reground crankshaft then I would assume that the crankshaft does not have enough depth of hardness to allow for grinding.
If the final hardening of the surface was nitriding or tuftriding then the surface would easily be all gone I think after .25 mm of grinding per face. If the engine only needs .10 mm of hardened material why add more?
In the old days you could regrind crankshafts, I think high performance engines these days require a new crankshaft.
When you mention polishing I think you mean grinding, 2 mm ( 1 mm per side) would have been too much for the old crankshafts.
You should check the truth of what I say but I am not too far wrong I think.
I'm sorry the news I give is not very good.