<VV> dressing down a knick
djtcz at comcast.net
djtcz at comcast.net
Sat Nov 13 19:09:09 EST 2010
----- Original Message -----
How important this is kind of depends up which part of the journal the nick is located. If it is on the main thrust part one should take great care to not create any kind of a flat spot. Your description leads me to think yours is on the side of the journal. Either way, if you look very closely, a nick usually consists of two parts. 1. An area from which material has been displaced and is lower than the normal surface; 2. the displaced material which is higher than the normal surface.
Do not be concerned with the area that is lower than the surrounding surface. Sandpaper of any type is not really the best choice so I would use a very fine honing stone and something like honing oil. Working with just a touch at a time. take off ONLY the portion which is higher than the normal surface. This is a fussy little job and very high power magnifying glasses and plenty of light are required. When complete the lower area will still be visible and the former higher area will be at the same level as the normal surface with NO flat spot.
As long as you are starting with mostly new parts it would probably be wise to replace the bearing shell.
I use some kind of solid backing behind "sandpaper" when I'm trying to flatten a high spot, whether on a machined surface or even truing up body work by block sanding. Abrasive on a flexible backing may create a finish, but not correct geometry. I'd compare abrasive paper used as a strip (shoe shine style) or backed by a finger tip to a glaze breaker or brush hone which just follow the cylinder's existing taper and out of round. I'd expect Fine Abrasive paper backed with a piece of paint stirrer or a flat file or an old bearing insert would do a better job of easing down a high spot than uncontrolled polishing. Painting the journal around the knick with Dykem or Magic Marker before and occasionally during the process can make it easier to see if there's a high spot left.
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