[boydage]

Small Chinese lathe with a 900mm bed and a 240mm throw. It was originally a manual machine I converted to a CNC lathe. I dont use it much but when I do its awesome to a point. I have a few problems I am addressing now and was hoping an experienced turner can pop some opinion into this post.

Wanting to control my motor electronically I installed a 2hp treadmill motor that didn't have enough torque. I am installing a different 1.5kw 3 phase motor with a VFD, it will have a huge amount of torque in comparison. But I am not sure what speed range to work on when I sort out pulleys. What would I want to look for at the chuck? 500-2000rpm? Or?

Too much backlash using the standard acme hand screws I am installing some ballnuts on ball screws to remove all backlash. I am going to leave the main carrier but for the Z axis, would I be better to take the gibbed plate off and replace it with good linear rails on the saddle to hold my tool holder and eventually a turret? Once I remove the backlash on this axis it needs to be reasonably tight to be satisfactory. If I put linear rails on I will be able to move that axis a lot quicker. But is it worth doing?

oh. Just two questions really. Thanks

[cncmakers001]

It is a small lathe machine.
Buying a new CNC lathe machine could be more cost-effective.
And less trouble.

[boydage]

It is a small lathe machine.
Buying a new CNC lathe machine could be more cost-effective.
And less trouble.

Dear cncmakers001. Might be for you my friend. You assume incorrectly. Perhaps if I was beginning right from the start, but this is an upgrade. If you have some good educated robust advice for me and this forum I offer a clean slate for your keyboard.

[atomarc]

My two cents...for a small lathe like that, you'll probably be using higher R PM's more than slow ones, but having said that, I think a sheave ratio to achieve the speed you've listed would be good. You can pick a middle of the road HZ (+) on your drive to get you those desired speed parameters, then be able to drop some RPM as well as over-speed the drive for anything higher...they can easily tolerate 120 Hz.

Regarding your cross slide/compound changes using linear rails, if you have room for that modification, I think it's a great upgrade.

Stuart

[boydage]

My two cents...for a small lathe like that, you'll probably be using higher R PM's more than slow ones, but having said that, I think a sheave ratio to achieve the speed you've listed would be good. You can pick a middle of the road HZ (+) on your drive to get you those desired speed parameters, then be able to drop some RPM as well as over-speed the drive for anything higher...they can easily tolerate 120 Hz.

Regarding your cross slide/compound changes using linear rails, if you have room for that modification, I think it's a great upgrade.

Stuart

Thanks. Worth more than 2 cents too. Great. Ok. I am into it. We think, we begin. I have installed the motor with a new adaptor plate. It didn't take long to rebuild the Z axis I bored out the saddle and inserted a 2005ballnut, threaded a 2005 screw I have and thats all good too. Just waiting on a keypad for the second hand VFD I bought, I cant seem to connect to it with my PC to program it.

The final upgrade is the X axis. It will be very easy to pop a couple of HG rails on the saddle and manufacture a new top to accept my post. I was actually thinking about making a turret - I need to research more. Like, is Mach 3 capable of toolchanges and the length offsets I would need is a question I need to find out. I was considering using a quickchange toolpost for a manual type of toolchange.

I guess I will get this done. And go back to using my cnc lathe once in 3 months. Or, I may find I use it all the time and am lost without it. Either way, its a cool project.