Not so easy!
The 3/4" - 10 TPI thread size is found in some of the Chinese lathes sold by HF and others. It is NOT the more common 16 TPI found in many smaller lathes. How do I know??? My first lathe, a $79 special at HF.... This size thread, 3/4" x 10 TPI is what you find in common bolts and threaded rod, and also, threaded rod couplers. That lathe does not even have a Morse taper in the spindle!
I have yet to find a commercial adaptor for this size. Needless to say, now I own a Jet Mini and a Powermatic 90.
I made several accessories for my first lathe, all based on the 3/4" rod couplers found at the hardware store. They are just like a long nut. Believe it or not, I managed to make a Jacobs chuck adaptor to hold pen mandrels, and it ran very true! I cut a piece of threaded rod about half the length of the coupler, and ground the ends flat. Then I used JB Weld to secure it in one end of the coupler. Using the Jacobs chuck with a Morse shank in the tailstock and a short drill, I drilled a hole in the middle of the adaptor. Tapped and put a stub 3/8" rod (cut from a bolt) to match the internal thread in the Jacobs chuck. I made many pens using this chuck and mandrel.
You could make an adaptor with a coupler and a 3/4" - 10 bolt. Cut a piece and JB Weld it in one end of the coupler. Then have the unthreaded portion that sticks out threaded to 16 TPI in a metal lathe....
By the way, that HF lathe is just sitting in a corner of my shop out of the way.
