On Thu, 26 Feb 2009 14:10:41 -0600, Don Foreman
wrote:

Leon Fisk noted the benefit of a thrust bearing. Note that it would
need to ride on a hardened disc or surface.

Now, consider a bolt inside a bushing that is threaded both inside and
outside. The bolt might be 18 TPI while the bushing on the outside
might be 16 TPI riding in a threaded collar. In use, you use two
wrenches, simultaneously rotating the bolt clockwise and the bushing
counterclockwise, effectively screwing the bolt "in" as the bushing
screws "out" (for RH threads). The result is a differential motion of
1/16 - 1\18 inch per turn, or 1/144 inch (.00694) net. You get the
benefit of thick, robust threads while the differential action
provides enormous mechanical advantage. Lube the threads with
high-pressure lube.

This thrust bearing:

http://www.mcmaster.com/#60715K15

has the following specs:

Part Number: 60715K15 $18.55 Each
Type Integrated Ball Bearings
Integrated Ball Bearing Type Shielded
For Shaft Diameter 1"
Outside Diameter 1-31/32"
Thickness 5/8"
Dynamic Thrust Load Cap, lbs. 6,700
Maximum rpm 3,800
Bearing Material Steel
Washer Material 52100 Hardened Steel
Temperature Range -40° to +250° F

Provided you can make something to go on the end of a 1 inch
bolt to hook the inside of the bushing.

--
Leon Fisk
Grand Rapids MI/Zone 5b
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