j.b wrote:it shouldnt be too difficult for a machine shop to knock one up, the davida spindle was threaded at both ends rather than the conventional bolt type spindle which would make machining a keyway either side easier.
That would make machining easier for sure, no big deal for any machine shop as you say. The big (only) issue with a nut at both ends is - you can't choose which nut turns when you tighten, so you can get the spindle turning through one of the nuts. You could machine a spindle threaded at both ends, so you can machine the keyeways, then weld a nut on one end. Or you could loctite one nut - then it's effectively a conventional spindle by another name.
I'm not disagreeing, just discussing.