I assume you mean 0.1mm steps, in which case, the best that can be said about a bore which will accept a 7.7mm pin and not a 7.8 mm is that the bore is larger than 7.7mm and smaller than 7.8mm. Use of any gage assumes that the operator is skilled enough to use it properly.
Standard pin gages are 2" in length, to use properly up to the full length of the pin should enter the bore. This precludes installing it at an angle. Standard pin gages are furnisheed in master sets with pins in 0.001" increments, permitting measurement to +- 0.001". If this is not sufficient for the application, individual pin gages can be purchased in 0.0001" increments. Ideally, for measuring a bore, a set of gages on either side of optimum would be purchased to determine the actual bore diameter.
