Thanks Paul & Bob.
I didn't have an drawings or anything like that. I just took a piece of round stock, figured out the size and internal thread of the lathe spindle and bored a hole that I thought would be big enough for 1"+ stock. Then I turned the part down to size and threaded it on the lathe. It is, of course, metric.
Then I drilled and tapped the four holes to adjust the stock to center.
That's it.
Bob