Accuracy of "sizing" carb passages

[Schurkey]

When using a number drill bit to determine the size of a carb passage; how close do exact size you need to be?

The number drill bits go up--or down--in size by several thousandths; there's any number of passages in my carb where one drill bit fits loosely; and the next size up won't go in at all.

Basically, I'm using the number bits as go/no go gauges.

Is that close enough; or should I be trying to figure out how to measure within a thousandth instead of several thousandths?

[Cliff Ruggles]

With small gaps between drill sizes, sometimes you will only get a good idea as to the size, and not the exact size.

In our book we tried to reference drill bit sizes as found in the 1-60 and 61-80 standard indexes.  We also give a range for some recomended holes sizes, so those drill bit sets could be used for custom modifications/tuning.....Cliff