A list of the most common abbreviations in use on working drawings follows. This list has been adopted for the plates in Machine Drawing Part I:

F. A. O............ finished all over.

f.............. finished surface.

R.............. radius.

D.............. diameter.

R. H............. right hand.

L. H............. left hand.

P. R............. piston rod.

P. TAP........... pipe tap.

CTRS............ centers.

C. I............. cast iron.

S. C.............. ...steel casting.

Bz.............. bronze.

C. R. S............ cold rolled steel.

T. S............. tool steel.

O. H. S............ open hearth steel.

W. I............. wrought iron.