As title, pictured with metric dimensions (but with imperial added into text), mine is made from a handy piece of galvanized scaffold tube.
First of we need the critical nut dimensions, thickness (which gives us the tooth length (0.2150") ....
Tooth width (0.2455")
Major diameter (1.809")
Minor diameter (1.6075")
Easiest method is use a broad tipped permanent marker to coat a wide band around one end, scribe a line to show tooth depth, then place the ring nut on top & scribe the teeth, cut the sides of the teeth with a junior hacksaw
Now grind/file the spaces down to the marked line
Overall length of the tool is (6.5")
The reason for it being so long is so that the "tommy bar" does not foul the tupperware, when drilling the tube for the bar it is necessary for the hole to be offset .375"
This is to allow clearance for the drive extension when torquing the top nut
My "tommy bar" is a handy piece of 1/4" diameter stainless steel rod 9" longStem
nut tool with octagonal top nut socket inside, viewedfrom below