Quorn Tool and Cutter Grinder, part 1A, spindle housing

[Toolmaker51]

From the dim and distant past, when there may have been only 11 HMT-er's, round about 10-04-2016, 11:57:59 AM;

Our own Mr. K, mklotz offered this perfect solution our favorite dilemma; boring and especially threading to a shoulder. It also applies for reliefs, O-ring or snap ring grooves, etc. I'll add it's effective chamfering corners, blind thread starts and general deburring with tool already in play.

Threading setup chart

The advantages are clear; these combinations take some mental gymnastics to recall. Instead, print this segment out, make a sheet-load of cards, laminate and distribute to metal working associates. Or tattoo your arm.
Either way, it establishes the 'code' of tool orientation with rotation of lead screw and spindle, he stated correctly;

A - Threading tool upright, point toward lathe back
B - Threading tool inverted, point toward lathe back
C - Threading tool upright, point toward lathe front
D - Threading tool inverted, point toward lathe front

L - Direction of feed = Left
R - Direction of feed = Right
f - Forward Spindle Rotation
r - Reverse Spindle Rotation

To Cut Right Hand External Threads: Lf(A/D) Rr(B/C)
To Cut Left Hand External Threads: Lr(B/C) Rf(A/D)
To Cut Right Hand Internal Threads: Lf(B/C) Rr(A/D)
To Cut Left Hand Internal Threads: Lr(A/D) Rf(B/C)

Cue the violas, he hates electric guitars.
Voila!

I'm sure nuclear ICBM launch codes weren't so intricate.....