On 01/25/2019 11:39 PM, andy pugh wrote:
https://www.gumtree.com.au/s-ad/picton/miscellaneous-goods/metal-working-lathe/1202880018?utm_source=Gmail&utm_medium=social&utm_campaign=socialbuttons&utm_content=app_android
Holbrook H20 / H17 at a guess. Absolutely top class lathe. Maybe the best,
I would be interested to hear of other candidates in that envelope. DSG
obviously. Graziano might be in with a shout. The USA folk are probably
shouting "Monarch" though this is a bit bigger.
There's also the late Sheldon R-series. It has a whole
BUNCH of features to improve the quality of the work. So,
the spindle gearbox is in the pedestal, and the only gears
in the headstock are for the backgear. The spindle is
driven by triple matched belts, to keep gear vibration out
of the headstock. The input pulley is coaxial to the
spindle, but does not run ON the spindle, it has its own set
of bearings in the headstock, so as to not impart any
vibration to the spindle. It drives the spindle (in high
speed mode) through a pair of hand-lapped drive dogs, so as
to not put an imbalanced torque on the spindle.
The QC box has 80 speeds, operated by two wheels full of
gears on needle roller bearings.
WAY more complicated than a car transmission. The power
feeds are driven by a keyed shaft which is driven by
U-joints, so as not to deliver any radial thrust to the
apron. They also drive the carriage and crossfeed through
clutches, not gears. The clutch break-away force is
adjustable, so you can be sure in a crash it will not break
gears.
The power feed and threading feed are engaged by pulling up
on levers that lock in place.
To release the feed, you just tap the lever downward and the
lock drops out, the lever drops and the feed is disengaged.
I have done threading of fairly coarse threads at 900 RPM
with no worries at all, you can stop the feed right where
you want to.
There's plenty more to it, but those are a few of the
highlights. The Sheldon R-series was made in 13, 15 and 17"
models. My 15" with six foot bed weighs 3500 Lbs. Good for
stability. My previous lathe was a 12" Atlas-Craftsman.
The difference in rigidity is just AMAZING! See
http://pico-systems.com/sheldon.html for the whole saga of
getting it moved in and fixed up.
Jon
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