Drawings for Nelson and Turbo Head buttons?

Turbo plugs are a 60 degree angle and the hole is 3/16". The tap drill size is 7.25 mm, and the tap is 8mm x 0.75 pitch. I found a good combustion chamber shape for .049s to be a 90 degree countersink. Maybe an 82 or 100 degree countersink may be better. I looked at a Merlin plug and that is what they looked like. I am sure Al Kelley played with a lot of designs before production. When I compared them to some old TD heads they were overall quite similar with the shape. Of course that is just a starting point and experimentation is due. The Nelson plug is a 118? degree or so angle. It is just whatever the standard drill angle is. The tap drill size is 1/32" less than the OD of 13/32" ? I believe. The depth of the plug to the bottom of the squish band is around .062" for an .049 and maybe .100" to .120" on a .15 IIRC. The hole size on a Nelson plug is about 1mm larger than the turbo plugs. That is why I prefer the turbo plugs for the smaller motors. I made a bunch of slugs that fit the plugs and left the combustion chamber and liner face blank for each motor. I made a .500" diameter step .100" deep to hold in a collet. 7/16" dia. would work maybe on a smaller motor. Have fun making them. I did. I have an old Hardinge chucker turret lathe, very high tech for 1952. Some heads were 7,000 rpm better than one I had been using. Most were 1,000 or 2,000 RPM better than a standard plug head. You may have trouble cutting a thread to fit a Cox. A Merlin or Norvel collar may be used, or use a burned out Cox or whatever head.