Re: Cross slide and compound backlash

glenn brooks
 

A good indicator of wear for cross or compound screw and nut is inconsistent DOC and finish when making final cuts. Slight concentric circles in the finish cut means the thread angles on your screw are worn, causing the tool post to ride up and down on the threads as it passes along the work. Same with holding a consistent DOC. A worn screw means sometimes never being able to achieve the same rate of removal.

my SB Fourteen had these same issues. Sometimes DOC varied up to .010” with the same amount dialed in. I had a shop make up a new screw and nut and now it’s rock solid.

BTW, both parts wear against each other. If the nut is worn, you can count on the screw to be worn also. If you are tearing everything down for a rebuild, why not renew the clearly suspect parts and make it new again?

Glenn

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