I tell you Rex it was not fun. I worried that I'd get to the last of the 20 holes on each part then break a tap at which point I would have been seriously bummed.
I believe the tap I started with is done as I'd used it quite a bit before I started these. I used a tap hole drill that was over sized by a bit as I wasn't shooting
for maximum strength rather than just enough engagement to keep the screw in line. As small as the screws are and as relatively long as the engagement surface is
it doesn't take a full depth thread to be plenty strong. To take part of the sheer boredom away I actually used my full sized electric drill to seat all 200 stainless screws and none
stripped out under that force so they are tough.

I'm convinced that 20 1-72 screws to fasten the sprocket to the drive output should be more than strong enough. A 1-72 screw is about 0.0730" ( 1.8mm) which works
out to about a 3/4" ( 18mm) bolt in full size and if you look at the image above of the full sized drive unit that seems pretty good. Probably a tad on the meaty side.

The core drive shafts are all 8mm steel. I've used 10 and 12mm for my larger models but I think 8mm will be sufficient for a pz III.

Right now I'm taking a rest from the sprockets and final drives and working on the idler rollers then to make the track tension adjustment mechanism.

Once I get these 5 models sitting on their own running gear I'll take a break from them to give me time to work out details, make a die to press road wheel caps, etc.

Jerry