Been playing around with a few concepts around the Sierra/Parker style transmission. Learned that there are at least 2 thread types out there - some are 8.5mm x 1 and other are 8mm x .75. I already had the 8.5mm tap and luckily the 8mm x .75 is a standard from Victor Machine which I got through Amazon for less than $5 with no minimum order. Here's one of my favorites. Transmission holders on nib and finial machined from brass. Except for the hardware, all cast PR with a little carving in between.