Re: [multimachine] Re: Lathe Spindle
- On 01/06/2013 01:38 PM, StoneTool wrote:
I would suggest that you try assembling something with that sort of clearance...............
Back in the 1970s I did, it was tricky, but not impossible (and that was many moons ago!) It took a lot of jigging and pressure, but it worked. The surface cleanliness was simply incredible (I worked in an optical encoder and metrology company.)
Air bearings are often sintered porous graphite these days (like a fish tank stone) and MUST be assembled with pressure on or they won't go. Put the bearing in the housing with o-rings to support and seal it, apply 90 PSI, press the shaft into place. The shaft is self aligning, there can be no steps as the shaft tapers to the correct diameter, but if the shaft starts at .002-.005" undersize with a conic section leading to the bearing surface, that is okay. It CAN NOT be assembled without air pressure, it just jams and galls. The stiffness is amazing -- 2 million pounds per inch!
The trick is the powdered graphite bearing, even with clearances of 1/4" (that is HUGE), the bearing has enough resistance to flow that the pressure can be maintained.
Read the New Way manual, the world has changed.
"Among the many misdeeds of British rule in India, history will look upon the Act of depriving a whole nation of arms as the blackest."
Mohandus Ghandi, An Autobiography, Page 446.