Twisted lathe bed – Portass Model S

[MuzzerParticipant @muzzer]

It's more likely to be a series of stepped diameters than tapers. The different sections of the spindle relate to particular features such as the back gear cluster (which spins on the spindle during its infrequent use), bull wheel (fixed), main bearings etc.

You'd probably want to measure it in quite a few more places and / or examine more closely for steps / shoulders along the length. There will also be some wear in places (mainly where the bronze bushes locate) but that surely won't amount to anything like the differences you have shown.

After allowing for the wear, it should be possible to make a reasonable guess as to the original profile. Sorry, my machine is on the other side of the Pennines, so I can't dismantle it to see what it looks like.

Murray

[Author]

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