Originally Posted by bigngreen
Huh, I think a guy could make a tool that used normal threads fairly easy. Maybe when I get some time I should try making one. I can see that using a fire case from your chamber would be more accurate.
Yes NF 5/16-24 would be sufficient don't know why they went with the off thread pitch unless it was to discourage folks from making their own cases. Oh and make the entire thing from METAL. The Hornady tool has a plastic inner push rod that dimples the first time you use the thumb screw on it making it rather difficult to take an average of 3 measurements cuz they all come out the same, should have used 1/8" SS round stock. I hate it when someone takes a great idea for a tool and goes cheapo on the materials they manufacture it from. Also, the Hornady tool features a sharp corner at the base of the thread relief which tends stress fracture with repeated use. When you make yours make sure to leave a small radius in that corner. If it is worth making make it right folks!
Bigbuck, check the yellow pages for a machine tool supply house. There is bound to be one somewhere nearby and if they don't have the tap/tap drill combo in stock order it through them and they will absorb the majority of the minimum order cost. You may pay a little more but won't buy a bunch of taps you don't need.