Symbols Used on Our Drawings

These symbols are used on the Mechanical Models engine drawings as well as on many other drawings.

	Identifies a surface
	Means that the indicated surface should be parallel to surface A within 0.10 mm
	Means the bore should be perpendicular to surface A within 0.05 mm
	Means that the diameter should be concentric to diameter A within 0.03 mm
	Specifies the diameter, in mm
	Specifies a thread. M3 means a 3 mm standard thread. 7H means a standard class of fit (that is, make it fit). The pitch for standard metric threads are as follows: Diameter   Pitch 3 mm   0.5 mm 4 mm   0.7 mm 5 mm   0.8 mm 6 mm   1.0 mm 8 mm   1.25 mm
	Indicates a surface finish of 1.6 micrometers, the same as 63 micro inches. That's a good turned surface.
	Indicates surface finish of 1.6 micrometers. The circle indicates that you should not remove any material, simply use the size and finish that is provided.