"Ignoramus11200" wrote in message
...
Look at this pictu


http://yabe.algebra.com/~ichudov/mis...Chuck-4545.jpg

This is a 12" lathe chuck for South Bend lathes.

My question is that the mounting seems to be a simple thread. There is
no "lock" like there is on L type mounts, or on camlock chucks etc.

So, it could happen that the big chuck would unscrew itself during
stopping if RPM was too high, the brake was applied too vigorously, or
something broke inside the gearbox. The chuck weighs about 100 lbs, so
having it bounce around the shop would not necessarily be a great
experience.

Am I missing anything?

i

No brakes. And if the gearbox breaks, duck. g

Threaded spindles are the traditional design for engine lathes. My 1945 SB
has a threaded spindle. It works fine. Billions of parts have been made
using them, in production and in toolrooms.

Newer locking designs are better. The threaded spindle is an old approach,
as is the rocker-type toolpost, the plain-bearing spindle, plain dead
centers with white lead for lubricant, and so on. They work. They're capable
of really fine machining. Hobbyists will be using them for years to come.

But doing commercial work with one of these lathes today is like delivering
parts in a Model A truck.

--
Ed Huntress