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Using bore gauge

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I've started using a bore gauge to measure the bearing clearances on my F20C, however the gauge is leaving significant scratches on the bearing shells that can easily be felt with my nail. I've tried to be as gentle as possible but cannot seem to avoid this occurring. The scratches will not polish out like you suggested in one of your videos. Is there anything I can do to prevent this happening? Thanks


The bore gauge I use has small teflon buttons insert into the end of the two contact points. This seems to reduce the marking on the bearing shells however some amount of marking is inevitable. The marks I end up with can't be felt with your fingernail and are more visual than anything. If you're getting deep scratching then I'd be considering a different bore gauge.

I had a similar issue where a couple of bearings sustained damage from measuring using the bore gauge. One of the teflon tips picked up a tiny fleck of steel which damaged the bearing surface as the bore gauge was rocked back and forth.

Is there a way slight marks can be polished out? I have bought a new set of bearings just to be on the safe side, lesson learnt!

Minor marks can be polished out by using the back of a piece of emery paper (NOT the abrasive side, just the backing paper) coated generously with a lubricant.