# Sherline backlash modification



## crueby (May 19, 2014)

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As a longtime Sherline owner (currently have a 4400 lathe and also a mill), one thing that I always had trouble with was keeping the backlash adjustment on the cross-slides in proper adjustment. Sherline has done a good job with the adjustment star wheels on the threads, but where I had problems has always been where the ends attach to the hand wheels. The small set screw on the hand wheel is all that keeps the threaded shaft held tight at the outer plate - and it always seems to drift with usage, opening up a small gap with the plate, and letting the cross slide chatter, especially in milling operations (the long axis on the mill table is the one I've had the most trouble with). I noticed the way that the CNC fittings were designed with a set of bearings and a preload nut - looks like that should work great, but hard to replicate on my own for the hand wheel setup which is non-CNC.

Recently had an idea to correct this flaw - I had obtained a spare end plate (did not want to risk messing up the one in use if the idea did not work!), and added on a second plate inside it to capture the fitting on the end of the shaft. Easier to show than describe, below are some pictures of it. I made the new plate out of brass to test the idea (it worked like a charm - holding really tight tolerance, easy to adjust). I may remake it out of steel. I am planning on making three more to do the other shafts on the lathe and mill.

[/SIZE]Here it is assembled with the shaft - the cutout in the new brass piece is to allow it to sit under the cross slide.


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Front view. As you can see, to adjust the new plate all I need do is remove the handwheel and tighten/loosen the two new socket head screws. I put on some removable loctite to hold them in place.
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Side view, showing the gap between the plates - the counterbore in the new plate is less than the thickness of the flange on the fitting, allowing for takeup if there is wear over time.
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Showing the pieces - the threaded rod and its fitting were not changed at all, and just the two new holes for the set screws in the existing plate:
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Here is a measured drawing of what I made if you want to make one. Since the existing plate was hardened, I annealed it, drilled, then rehardened and tempered it again:
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