Fabricated external lathe gearbox and finally managed to test it. I run it for very short time in order not to destroy gears. No oil in gearbox.
As there are couple of people who couldn't wait to see it in operation (rossbotics wrote: Looks great, cant' wait to see the finished product)
I posted it now before it is completely finished.
I would assemble it completely in a day or two and fill oil inside (ISO 46 hydraulic oil) and buy 925 mm v-belt (presently 900 mm v-belt is outside pulley groove), but I received an urgent call from crewing manager and had to pack my luggage and join the vessel very urgently. So that has to wait until I am back home again. Then I will post video of assembling gearbox and with fully completed gearbox (painted as well) in use.
Poor design of belt change and bad choice of spindle speeds made me to do something about it. Whoever has this type of lathe knows exactly what I am talking about. I was thinking about this project for a couple of years already and during my last contract I spent more than 3 months calculating speeds and what gears to buy. I made so many calculations and I made more than 500 different drawings always changing something. There was also an idea to have 18 speeds, but that would be overkill. Still there is possibility to install two additional gears (55 and 33 teeth) and get additional 6 spindle speeds: 125, 250, 375, 500, 750 and 1500. It can happen. I am in China again and gears (google translated it from Chinese as precision spur gears #45 steel tooth surface induction hardened) are very cheap here. Chinese gears for Chinese lathe.
Total weight of gearbox is close to 50 kilograms and that's the reason why it sits on very strong support. It is also placed far away from the chuck so it is not in the way of chuck key.
Once I was happy with my calculations and drawings, I bought all that stuff which can be seen in attached pictures.
What can't be seen in video is that I also installed drain plug at the bottom of gearbox (smaller oil eye glass) and glued rare earth magnet inside in order to collect steel particles.
mild steel, SS 316 and SS 304
I estimate that I spent little bit less than 100 dollars for all material, but now I have fully functional and user friendly lathe. Needless to say that I spent plenty hours of my vacation time for fabrication of this gearbox.