Re: grinding crankshafts?

[bearbvd@domain.elided (Greg Hermann)]

At 11:39 AM 10/4/01, Watry, Andrew (LNG-MBC) wrote:
>This is a general question, not Alfa-specific, that has bugged me for
>years/decades. I can imagine how a machine shop grinds the main journals on
>a crankshaft, because they are on a common center/axis with the shaft
>itself, so you can basically stick it in a lathe and turn it.  Is that how
>it works? But how does a machine shop grind the rod journals, which are
>off-center and have no chuckable axis? I can't picture how it would work.
>Thanks
>
>Andrew Watry

A crank grinding machine has "face plates" on both the head and tail stocks
which allow offsetting the centers by an adjustable amount equal to 1/2 of
the stroke (or more if one has the crank "offset ground" in order to
"stroke" it. It is also possible to rotate the crank in the offset position
in order to grind the various throws on it in the proper angular
relationship to one another.  On the best crank grinding machines, it is
possible to index the throws on the crank relative to one another
(degreewise)  more accurately than what was done at the (some) factory
(ies).

Greg

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