Really useful video, thanks Cliff. That's got me thinking about the subject in much greater depth. In the past I have done odd jobs on my manual lathe and used a couple of normal 'flat bar' parallels to set my round bar square in the chuck, but obviously taking these out once the stock was tightened up, and I was under appreciating how little stability then remained against machining forces. For one-off jobs I got away with it, but I need to re-think about spiders now. I am considering purchasing a Tormach CNC lathe soon, so even more relevant for the future. Thanks for the excellent advice.

another great video! great explanation. I wanted to make spiders for my lathe since i got it, but somehow i can not force my self to make one :) have you consider making a new product? i'm sure there will be quite few people interested.

Excellent idea. You didn't cover the making of the stops. How do you overcome distortion when the large slots are machined? Are the stops scrapped to parallel after machining? Thanks