The following Standards identify the recommended lettering requirements/geometry to be used on engineering drawings....
The standards provide detailed lettering dimensions
and methods of identifying the text used.
The text is identified by a nominal outside hieght
size (h). The preferred text sizes are
listed as used are (in millimetres )
1,8 2,8
3,5
5 7
10 14
20
Note; I am using commas as the decimal marking in my
attempt to adhere to the new BS ISO requirements...)
For lower case letters the letter height (height of
say "a" ) = 10 / 14 x h. The
height of the tail (on say g) is 4/14 x h and the
lower case stem (on say h) = 4 /14 x h.
The line thickness is set at 1/14 x h. A typical
designation of the lettering used on a drawing is ISO
3098- BVL - 5
B is lettering type ( A, B,
CA, CB)
V is Vertical ( Can be S
sloping)
L is Latin Font ( Can be G =
Greek , or C=Cyrillic)
5 is the nominal size.
Note: The A and B types are intended for lettering
drawing using stencils or tracing from a graphed
lettered sheet. The CA and CB are for CAD
systems.
I have checked out the ISOCP.shx font that comes with
Autocad 14 and it seems to conform pretty well with
the Font in the standards above for the Latin font.
I include below this note a set of Latin
characters drawing using IntelliCaD Professional with
the isocp.shx font.
Note: This is confirmed by the ISO link below which
provides a full set of downloadable fonts for
Autocad.