Disengageable leadscrew handwheel with
60 divisions dial
This setup has been working on the lathe for more than a year, but only now the 60 divisions dial was made. It is my second run making a leadscrew handwheel. The first one was one of my very first mods but I was never happy with it. After making the disengageable handwheel for apron, decided to make also a disengageable handwheel for the leadscrew, as it is good to disengage it when using autofeed.
After thinking for a while, decided to make the graduated collar with 60 divisions. This lathe has a metric 1.5mm pitch leadscrew so, with a 60 divisions dial, each dial mark is 0.025mm. Exactly the same as on cross-slide and compound dials.
Here are all the parts. A cast iron pillow block was made on the lathe, bored on both ends for the bearings. The leadscrew end was machined to 12mm to fit into the bored end of the leadscrew extension made. The thread on the leadscrew extension is for preloading bearings, to remove backlash. Bearings are 6201 (12x32x10mm) that I was having on shop, from some stuff I dismantled on past.
The collar close to the bearings and pillow block is inserted on the pillow block, after the left end bearing. The leadscrew spring cover fits on it, for the leadscrew to rotate freely without contact with the leadscrew covers.
This is the collar for removing backlash. A tommy bar on a 3mm blind hole is used to tightening it and a point ended setscrew used to lock it in position.
Here is the o-ring fitted to the groove on collar. The o-ring is used to make the needed friction to keep the dial in possition, while it allows zeroing the dial very easily.
You can see that the collar was made with a recessed end, and the graduated dial was bored with an end on a smaller ID. This way, after installing the coupling collar with male dog, the smaller end on graduated dial will run on a groove between the two collars, preventing it from sliding back.
The coupling collar with male dog is secured in place by a 4mm setscrew that fits on a milled flat on the leadscrew extension. A circlip on a groove on the end of the leadscrew extension prevents the handwheel from falling while disengaging the handwheel.
Here it is fully assembled. This final aluminium part was made mostly for a cosmetic reason. It is bored larger on the right end for the coupling collar on handwheel to slide freely. A close fit on the left end, and two drops of loctite, keep it in place.
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