Key for IBM 9370 - 20

Dennis Boone drb at
Tue Nov 26 16:40:44 CST 2019

 > I need to get the information on measuring the depths of the cuts, as
 > the postings I've found don't mention how the depths are measured for
 > each value.
For Chicago/ACE, cut depths from 1 to 8 respectively are:
0.0155" 0.0310" 0.0465" 0.0620" 0.0775" 0.093" 0.1085" 0.1240"

For Fort/GEM, depths are numbered 0 to 7, but the measurements are the
same as for Chicago/ACE.

Looking into the end of the key, pin numbering is:

Chicago: #1 at eleven o'clock, proceed counterclockwise to #7 at one

Fort: #1 at one o'clock, proceed clockwise to #7 at eleven o'clock.

Presumably they had to avoid a patent. ;)

Offset rotations of the pin placements are possible.  The non-rotated
kind has the indexing pin halfway between pins 1 and 7.  For Fort/GEM,
if the #1 pin is further from the indexing pin, it's "left offset"; the
opposite direction is "right offset".

Secondary cuts are possible, where there's another channel cut into the
same rotation as the primary cut, but shallower into the wall, and
further along the length of the wall.  Hopefully that's not involved

 > I have an ACE key for an IBM 9370 mod 20 I'm measuring.

Questions -

Does it have a number stamped on it?  I'll try to look it up if so.

Do you know if these are per-machine, or all machines the same?  I'd
like to collect the data in case it's the latter.


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