<VV> turn my crank

[Tony Underwood]

At 06:22 PM 11/2/2006, AeroNed at aol.com wrote:
>
>In a message dated 11/2/2006 7:55:19 P.M. Central Standard Time,
>tdrinkr at yahoo.com writes:
>
>what is  done when a crankshaft is
>turned? And what are the consequences of doing  this?
>I.e. will over-sized bearings be  needed?
>
>
>
>
>The crank is placed in a lathe so that the main and rod journals are  located
>in the center of the spinning lathe. A cutting tool, basically a sharp  of
>steel, is used to remove a small about of the journal. The amount of the
>material removed depends on how bad the journal is originally. The 
>goal is to  cut
>all of the journals to the same diameter. It is not uncommon to have 
>the  mains
>at one new diameter and the rod journals at another.
>



There's a bit of a trend lately, with damaged cranks, with the shop 
checking the journals and if only one is damaged, they weld up on 
that one journal and turn it back down to STD so that the replacement 
bearing set remains STD as well.

This only works if the rest of the crank journals fall within factory 
specs.   A good shop will also insure that there's no warping or 
other issues.    I've known cranks done this way to work out fine, no 
problems.    It's also generally a little cheaper than setting up the 
crank to turn all the rods; easy to do all the mains but the rods 
require resetting the crank 6 times.    I watched a guy weld up like 
this, work piece was chucked in the lathe, spinning very slowly, he 
went after it and laid down a bead like he was feeding rope onto a 
spool, finished the weld in almost no time, looked fine...  turned 
the journal back down to STD at the same time on the same lathe, 
entire process from start to finish took less than a half hour, from 
the time he picked up the greasy crank to the time he stuck it on the 
outgoing rack with a billing tag on the snout.    Of course, he'd 
been doing this sort of thing for a while...  ;)

Either way, it's a good idea to stick with reputable shops if you 
have a crank turned, and check the work out for yourself after it's 
done, can't hurt.


tony..