12-29-2005, 06:48 AM
|
| | | Join Date: Dec 2005 Location: USA
Posts: 3,319
| |
To a point, I can agree with runner4404spd re: osize balls not preloading a nut.
If you have a ball screw with simple, radius ground or rolled raceways, the installation of oversize balls reduces radial clearance it but will not necessarily preload the system in the proportion hoped/intended.
Reason: The radius of the raceway is slightly larger than that of the ball. Thus, the ball tends to ride in the "crotch" of the raceway and, as axial thrust is applied, it rides up the side of the raceway - ala a bowling ball running down the gutter. A larger ball will make the radii closer but there is still going to be room for the ball to move axially up the side of the raceway.
HOWEVER, if the raceways are ground with a gothic arch, the installation of o'size balls will preload the system and reduce if not eliminated any backlash.
The g-a system effectively puts the balls into a "4 point" contact with the outer and inner raceways. Thus, you are sort of putting an "oversize round peg into a square hole" and can't help but experience axial preload/slop reduction.
Anotherthing to remember with o'size balls, we're talking o'sizes in terms of 0.0001" or so. It is also adviseable when installing o'size balls to alternate the size. That is if S=std and O=+0.0001, you'd load them SOSOSOS. This helps them roll more freely into, out of and thru the raceways.
Helpful hints to use when you're trying to turn a Ford into a Ferrari.  |
Linear Mode
