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Scretches when measuring bearing shells

Practical Engine Building

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When measuring main or big end bearings the bore gauge leaves some scratches on the thin bearing coating. This is ok on old bearings that will be changed anyways. But how to measure on new ones? Is there a way to do it with the bore gauge or should I use plasti gauge?

Hello Philipp,

Personally I don't use bore gauges if I can help it and much prefer Bowers type internal micrometers as they're accurate down to 5µm https://www.bowersgroup.co.uk/ but they're not the cheapest solution.

A bore gauge is usually OK to measure ID of new bearings, there will be visible contact marks but these shouldn't be able to be felt and wont effect the life of the bearing; however you need to ensure the bearing and bore gauge contact points are clean from debris.

Plastigauge is OK as a sanity check and better than nothing if measuring equipment isn't available but for a high performance, competition engine build where we require tighter control of tolerances I'd avoid it.

Mmm, been checking their product ranges - some very nice bits of kit there!

Some additions made to the LOTTO list... ;-)

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