Star Lube-Sizer: What is the thread size/pitch for the bullet punch?

[Rock]

I acquired an old beat up star lube sizer.
But I'm having trouble figuring out the correct thread size/pitch for the bullet punch.

Hoping someone can point me the right direction.

[edp2k]

outer diameter of the threaded part of my bullet punches are 0.490"

thread pitch is 27 threads per inch.
this is a very unusual pitch, so much so that you can't even single point cut these threads
on a lathe with a normal gearbox for driving the lead screw :-(
my friend's south bend can do 26 and 28 but not 27.

one way is to buy a specialty 1/2-27 adjustable die from mcmaster-carr/mscdirect/enco/etc.
and adjust it so it cuts a smaller diameter thread.

the star design is (I believe) from the 1930's, and back in that era many machine tools
companies made proprietary parts so customers were forced to buy parts from them.

[dragonrider]

I use just such a die to cut the threads for the punches I make for my Star. .490" dia is not a special size it is simply a 1/2"X27 TPI and adjusting the die smaller is not needed or recommended. I cut my punches to .500" and thread with the die they fit perfectly. Measure any 1/2" thread and they will be anywhere between .490" and .500" and many will be much less. As said above it is an odd thread size and I think deliberatly so in order to be somewhat proprietory.

[Rock]

Once again you gentlemen prove that this forum is an amazing place with awesome people who share their knowledge.
Thank you both!