Hello Everybody!

I have a D180x300 lathe, essentially its a copy of the Optimum mini lathe. I have made quite a number of mods, like scraping the saddle and top-slide. I have managed to get it to the point that I can take fairly deep cuts in steel.

However, engaging the leadscrew is slightly difficult, seems like there is not much tolerance and the carriage can even start moving if I dont manage to get the threads to engage. This is actually a minor problem, the bigger problem is that if I am taking a deeper cut, say 2mm off the diameter or more, then the half-nut is very hard to disengage and if I am taking anything deeper I essentially have to stop the lathe and run it backwards to be able to disengage the leadscrew.

At my fathers place I have a myford 7 and I dont recall having that problem with that machine.

Does anyone else have problems disengaging their half-nuts on their mini lathes?

Edited By Benny Avelin on 24/02/2017 09:45:34

Hey George, are we having fun

Bazyle, I have a picture from the manual so you can see how it works. It is an adjustable dovetail that I maybe need to adjust now that you got me thinking of canting over, there are no burrs as far as I can see. Isnt this exactly how the Myford is constructed? Maybe the range of motion is so small that when under high pressure the flex is so large that there is no way of disengaging?

Edited By Benny Avelin on 24/02/2017 12:49:56

Oh, this is an interesting problem. Actually I noticed the leadscrew moving while engaging the half nut back when I got the lathe. The way I adjusted it was as follows: I first moved the carriage to the tailstock end and engaged the half nut, then tightened the right mount for the leadscrew. Then I moved the carriage to the headstock and tightened, then back to the tailstock again and then to the headstock again to really avoid any height differences. After that I changed the position of the apron so that the horizontal movement at the middle of the leadscrew was visibly nonexistent. The movement of the leadscrew was invisible to my eyes, but per your suggestions I re-checked it and this time with an indicator. The lift is 0.1mm and the horizontal shift (toward the operator) 0.04mm. I am unsure about tolerances but this seems unproblematic.

Next, I checked the dovetail and it seems tight and smooth, there is however lots of play in the actual lever mechanism, I think this is the two pins sliding in the slots of the disc (see sketch above). Interestingly it is enough to try to turn the handwheel when the lathe is off and the half nut engaged to have trouble disengaging it, and even more interesting is that its much worse in one direction, i.e. the one that I experience while turning. Maybe I need to disassemble the apron and check everything.

Thanks for the suggestions, this forum is great!