What lathes have 2 1/2-6TPI spindles

Old ones, mostly. I might have one that size in my herd, or it might be

2x6 and one is 3 or 3-1/2 x 6 (haven't really been looking for anything for them, so it's been a while since I measured them). Both late 1800's flat belt drive Babbitt bearings.

LH or RH thread? The patternmakers lathe (smaller spindle of the two) has a LH outboard mount.

I thought it was RH thread.

I really "do not understand" why would anyone make a spindle like that. With a faceplate this big, a big part could be mounted on it. If the lathe is stopped, the whole assembly could unscrew from the spindle.

i

You've noticed why all the more modern spindles moved to a positive drive / lock design like the L and D spindles.

My old clunker Leblond has this. No brake to stop the spindle, let it coast down. I kept the old girl. It is handy to have a 20" by 120" lathe for light hobby use.

Karl

ote:

That is probably why it didn't stop very fast. Probably used an overhead powered flat belt system that was slackened to slip the drive belt off the pulley. Then if the faceplate was still turning, a stick of wood could be used to stop it.

Paul