Piston Sizing

[Bob Culver]

Everyone should have a 1inch or metric micrometer. The conversion 25.4 is dead accurate so either does. For most purposes a quality vernier calliper is adequate. I find the 8"' easier to handle than 6"'. Direct reading OK with a magnifying glass; does not give a false sense of accuracy. Greatcare necessary no to burr the tips etc. A gap of .0001" is visible against strong light.I f filing nails is too tediuous can make up a threaded tube and long screw with locknut. Hold with a clothes peg or some such. Laregr micrometers really need tets pieces to check the zero.T Unless badly mistreated in the past,  the accuracy is usually more in the use than the instrument Any oil film can add .0005 or more.