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View Full Version : 12" swing lathes with hydrodynamic bearing spindles



Elninio
06-25-2010, 11:06 PM
There's a nice 16" swing romanian toolroom lathe for sale with hydrodynamic bearings where I live - only $1900 too - but its too damn big! Does anyone know if there are smaller lathes using this spindle technology, say with 12" swing and a max of 40" length capacity? The brown and sharp 1024 has an oil pump for the gears but not for the shaft. There's no particular reason for this, just interested if they made them that small.

Robin R
06-25-2010, 11:22 PM
I thik you are refering to plain bearings, so that would include many South Bend lathes. Also many very high quality toolroom lathes also used this type of bearing. If the oil is pumped to the bearings under pressure, they would probably be refered to as hydrostatic bearings.

saltmine
06-25-2010, 11:27 PM
Actually, Hydrodynamic bearings were used on early Ford flathead V-8's.

The bearing consists of a number of leaves (of bearing material) that touch the crankshaft. Oil is forced in between the leaves, thus supporting the crank on a film of oil.

They must not have worked too well, as Ford dropped the idea after a year or so, and went back to more conventional bearings.

Interesting idea, though. Might work much better in a machine tool than an old flathead.

lazlo
06-25-2010, 11:28 PM
"Hydrodynamic Bearings" sounds cool, but it's just your 200 year-old plain bearing.

Hydrostatic bearings, on the other hand, are very slick - the spindle floats on a carefully pressurized fluid -- an air bearing is the most common example. The LODTM (ancient now, but claimed to be the most accurate lathe in the world, 20 years ago) uses an air bearing spindle.

Elninio
06-26-2010, 01:28 AM
http://sites.google.com/site/dannympwillems/
This link shows a restoration of a lathe with hydrodynamic bearings. He says the oil is fed under pressure on page 6, so I guess they are hydrostatic?

The wikipedia on these bearings tells the difference between hydrostatic and hydrodynamic: http://en.wikipedia.org/wiki/Hydrodynamic_bearing , but this definition is clearer (second post): http://www.eng-tips.com/viewthread.cfm?qid=232654&page=3

ptjw7uk
06-26-2010, 04:31 AM
Oil feed on page 7, near bottom.
I think the previous owner didnt understand the problem, stopping oil leak by not supplying oil?

Peter

Elninio
06-26-2010, 05:33 AM
Oil feed on page 7, near bottom.
I think the previous owner didnt understand the problem, stopping oil leak by not supplying oil?

Peter

Correct, in fact he says the spindle would cease on running more than 400rpm