|Grain Size Measurement|
| A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Definition:  Grain size is normally quantified by a numbering system. Coarse 1-5 and fine 5-8. The number is derived from the formula N=2n-1 where n is the number of grains per square inch at a magnification of 100 diameters. Grain size has an important effect on physical properties. For service at ordinary temperatures it is generally considered that fine grained steels give a bettercombination of strength and toughness, whereas coarse grained steels have better machinability.