When building worms I place a long manderal in the lathe with a loop welded near the end that fits the tailstock. The manderal must be small enough to allow for springback. Place the end of a long piece of round in the loop. The lathe in the slowest speed, turn it on and feed the round by hand on down the manderal. There is a picture of this operation on my website, click on my banner, go to the gallery, then to Cannon const.
Sant Dave, I should be able to provide a worm. I'll give you a PM. hopefully our mom and pop phone company will keep my internet working now.
Rick