has anyone thought of tapping a acme screw at the opposite side of the motor end. using a bigger bearing for strenght and cutting a hole through the bearing block , so you can put a washer and a bolt to hold it tight to the screw , thus clampping down on the bearing which is pressed between the block and the plate to eliminate backlash.[acme srcew would be milled to fit bearing.]would this be a good idea or would the bearing blow out .i hope you get the idea here. would like reply from the mighty cnc masters as im a newbee , and would like to use this idea on my cnc table. for extra measure.
You might be confusing slop in the bearings supporting the screw verses between the screw and nut. What you describe is a function of support bearing preload. Setting the preload is based on the bearing type and size. Simply put, the screw should be captured between the bearings so there is no movement of the screw shaft when the load changes direction. This can be done with shim washers on the screw ends between the bearings inner race and the shoulder on the screw or between the bearing blocks bores and the outer race faces. You could make this adjustable, but you need to make sure the bearings do not get tipped off square to the screw centerline. If you have some adjustment in the bearing block mounting fasteners, the blocks may need pinned in place to keep them stable first.
Backlash is primarily slop in the screw thread to the screw nut on reversal of the screw direction and no motion. This can be resolved by using a compensating nut. Which is basically two internal threads that can adjust to displace place their pitch distance between them, but still allow the screw to move through them.
Last edited by One of Many; 02-21-2009 at 01:01 AM.
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