I'm tossing around the idea of making my own CNC lathe from scratch. $2300 after shipping gets you a gear-head 12x36 import with fit and finish issues all over. A CNC conversion gets rid of all the threading gears, the direction changing levers, the rack and pinion, the threading leadscrew, and the cross-slide leadscrew. Seems like a waste. On top of that, you still have to buy the new ball screws and mount adapter plates before it's ready for the steppers/servos.
That same $2.3K can get you some bigass THK linear rails and blocks, a nice 2-3hp Baldor/Leeson 3-phase motor, a VFD, some smaller THK parts for the cross slide components, all the necessary ball screws, and enough money left over to fabricate the rest of the lathe.
Due to the lack of a foundry, it'd have to be made mostly of steel, probably similar in appearance to the Oneway wood lathes.....
I looked into this but the big stumbling block is getting a quality headstock. I was planning on using a 4" Granite surface plate for the bed. I don't really like steel as it resonates like a bell and this will effect accuracy and surface finish.
In the end I picked up a 11" Hardinge TFB for $2300 and will be retrofitting this with a 2HP vector drive, servos and GRex running MachIV.
Forgot to ask, are you talking about woodworking or metal working lathe?
I have been thinking about doing just that for the past two years
I mean, I have been hunting eBay for the parts.
Currently I have
- two THK HSR45 large 1m linear ways for the z
- one 25mm diameter 980mm C3 ground NSK ballscrew
- two 400mm Hi-Win linear ways for the X
- one 10mm 350mm C5 ground STAR ballscrew for the X
- 1.5kW Optimum speed controlled DC motor with controller
- one spindle: it was built by a guy in Germany who was making his own CNC lathe too but had to stop due to personal issues. It features 6 bearings, is over 300mm long and accepts a 100mm chuck. I measured more or less 1/100mm circular error...
Currently hunting down eBay for two 1200mm long THK HSR25 linear ways as the HSR45 are HUGHE. They have to be bolted down with M14 screws and I think they'll be too high for the lathe.
I was thinking to bolt everything down on a 2" thick aluminum plate that's been trued on a large shaper, mounting the Z on two aluminum extrusion (probably rexroth 90x90mm profiles as I can get them at the same factory where they shape the large plate). Milling the top mounting surfaces flat and then bolt everything together
The headstock is already in a 80x80 extrusion so I'll put it on top of another extrusion or casting to get it to height.
Also I plan to fill the extrusion with concrete when done, but the plate and extrusions alone will be very heavy...
No finished plans yet as I wait to have all vital parts here (waiting for the Z linear ways).
My only problem right now is for a good tailstock design and how to mount it to the rest.
Would be great to exchange ideas! I should get the final parts (rails) for Easter.
I would be tempted to do this the easy way, go find an old machine of the size you want that is allready equiped with ball screws and hang a new control. The iron does not wear out, it only gets better with age, and these machines get dumped because the original controls make them uncompetitive for jobs.