Stupid question

I'm sure this is not a question which I should need to ask, but do rebore
sizes refer to increase in bore diameter, or to thickness of material
removed from cylinder wall?
I had always assumed the former, but, I have just had to order a new ring
for S-T Type N (yes I know!) which wears a brass tag reading +0.010. The
bore however actually measures 1.7690" (digital verineers on unworn area).
Assuming standard bore is 1.75", that is pretty much 20thou oversize. So,
have I been wrong in my assumption or has the engine had another rebore?
Margaret Maddock ( advised sending an old ring to avoid
any mistake, which I have done.
Reply to
Nick H
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I see this question really was too stupid to warrent an answer!
Trevor Maddock has confirmed existing ring measures up as 1 3/4" +.020, so I guess the tag on the engine is wrong and the engine has had another rebore. Sadly new ring is not off the shelf like Martin's Bradford oil control ring, but at £15 still not too bad.
Reply to
Nick H

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