Been doing lots of reading on the forums lately and this thread

http://www.cnczone.com/forums/vertic...the_build.html

has really caught my eye. I have a bunch of HSR25 THK rail and I though man that could make a great lathe. I would like one that has a distance between centers of a couple feet IE 2-3 maybe 4. Most of the stuff I do won't be more then 12 inches long including whats in the chuck.

So here is the question I want a 3 inch Spindle bore. What is the minimum size you would make this lathe? Any reason to make it much bigger then the one shown in the linked thread? I don't plan on putting parts in it that weight more then 30 lbs at most. Is there a reason to keep the bore small?

is it going to mainly depend on the chuck I use? IE a 8 inch chuck with a 3 inch bore so my headstock needs to be at least 4.5 inches above the bed plus whatever the ears stick out on the chuck?

Oh yeah this is going to be doing 4140 and 4340 steel mostly. Might end up doing touch ups on hardened steel.

Just wondering. not sure if I want to build the whole headstock myself or if I am going to find a salvage one somewher. Any input would be great. Thanks all.