Andy
Left handed threads are easy. You just start at the left and go right.

Phil, I have machined many double lead stem nuts.
You really have to keep your mind on your work and don't let the boss tell you how to do it.
Ever do a buttress thread?

I also agree on the Balder grinder. They are the best made.

Don

1967 GMC 9500 Fire Ladder Truck
"The Flag Pole"
In the Stovebolt Gallery
1946 2-Ton grain truck
1946 3/4-ton pickup,
1953 1-ton pickup
1957 1-ton flatbed dually,
1954 Pontiac Straight Eight
Of all the things I've lost in my life, I miss my mind the most!