Actually half an inch and .5 inch are technically the same, it is the precision of the dimension that matters, for instance, (no offence meant) a builder / bricklayer may build a wall to an accuracy of +/- 1/8 of an inch and consider it perfect, the toolmaker will cut and grind a piece of steel to an accuracy of +/- .ooo1" before being satisfied, .001" under half inch could be scrap in certain circumstances.