How is the distance between centers measured, and is it consistent among the manufacturers. For example, my PSI 12" midi is listed as 18" between centers. The actual measurement from the end of the headstock spindle to the fully withdrawn tailstock is 19 1/2" (with the tailstock exactly at the end of the ways). If I insert a small 2 MT pronged driver I get 18" from the drive center to the tail stock. If I put my shortest revolving tail center into the tailstock I get 16 1/2". I'm not complaining - we all use various length devices on our lathes, large chucks and long revolving centers - it is impossible for them all to result in the same distance between centers.

I raise the question as I'm looking at the possibility of upgrading my lathe - specifically the Oneway 1224. But I don't know what the "24" means in practice. If it is the distance between the the end of the headstock spindle and the retracted tailstock end then I'd gain only 4 1/2" in spindle length. If it is measured from the tips of a small prong driver to a small revolving center then I might gain more than 6".

My guess is that there is no consistency and one need to measure for one's self. This is not trivial, I have a very small shop and have to allocate space. I have an extension for my PSI that I set up when I'm turning tool handles - the only long spindle application I do. I'm not going to buy a new and longer lathe if I need an extension anyway.

Is there a standard in the specs for distance between centers? Or is it the usual caveat emptor.