crankshaft scratches

[gnavs]

So I'm in a bit of a delicate situation.  I've got my crankshaft out and ready to be machined for the TDI pulley and notices some slight marks where the main bearings go.  I've been told to machine it .25mm if there are any surface marks that can be felt with a fingernail, and I definitely can, but I'm wondering if I can just smooth the marks with some emery cloth or sandpaper instead.  Money is starting to run tight but i definitely don't want to cut corners where I shouldn't be.  Should I bite the bullet and head to the machine shop?

[truckinwagen]

I would take it to them and see what they think.
you can polish some scratches out, but the machine shop will be able to tell you if you are in that realm.

[rallydiesel]

If you can feel them with your fingernail and get rid of them with emery cloth, chances are good you will have low oil pressure. You will probably have to go ahead and get the crank undersized and get the proper bearings for it.

[Henchman]

What did the bearing surfaces for the scratched journals look like?  Normal wear like the others, matching scratches or advanced wear as compared to the others?  If it is the first 2, I would not worry about it.  If it is obvious that the journal is eating the bearing surface, then you'll have to go over.  Keep in mind, that scratch could have been there from the first time the engine was run.

Ian

[clbanman]

What is the direction of the scratch?   If at 90 degrees to the rotation it will reduce the life of new bearings substantially faster than if it is in line with the rotation.  IE - acting like a file versus a knife.