Strip down the Blidgeport - prepare to machine the yoke for ballnuts

Not The Shiz as such - but it's still CNC milling machines, so hey. 

The Bridgeport CNC conversion - state of play:

Before I had that nasty accident with the mouse when I was browsing ebay and ended up with 3t of Japanese iron, I was in the process of converting my Taiwanese Bridgeport clone to CNC. I had made or acquired 90% or so of the parts required for the conversion - then we decided to move back to the UK. The move and the subsequent  period in a rented house put the kibosh on any workshop activity. And I blame the resulting cabin fever in part for said nasty accident with the mouse....

By the time I boxed up the workshop for the move, this is what I had for the CNC conversion:

• Z axis pretty much complete. Leadshine closed loop stepper motor, aka "Easy Integrated Servo" - nice 2Nm stepper with integrated encoder and driver. And the ballscrew / yoke assembly to drive the quill.
• X and Y axis ballscrews. I got these from AliExpress, machined to my own dimensions. Although they are rolled threads, they will be a massive improvement on the worn out leadscrews and bronze nuts which are pretty much "ready" now after a hard life. The backlash was pretty special although fitting a Chinese DRO transformed the machine.
• Various Taper Lock pulleys, belts etc.
• Jetway fanless mini-ATX format PC with Linux operating system running from an SSD.
• Mesa 5i25 (in the PC) and 7i76 (remote expansion card). Beats a crappy parallel port breakout board into a proverbial cocked hat and eliminates the risk of latency.
• DMM-Technologies DYN-2 servo motors and drivers for the X and Y axes. Originally I'd planned to use the Leadshine closed loop steppers for the X and Y as well as the Z but then I found the DMM-Tech systems which come in at a similar price but with the performance of true servos. Rather like the CNCdrives servo drivers I bought for The Shiz, they are clearly not industrial quality (I opened them up to take a look) but this is a hobby conversion after all and has to be completed on a hobby-sized budget.
• Several Mean Well power supplies to run the drives - these claim to be tolerant of overvoltage surges due to rapid deceleration of axes. And a variety of cables and connectors.

And I'd made up some of the stuff I couldn't sensibly procure:

• The Z axis assembly, as mentioned above. This was the first part of the conversion I tackled, as it seemed the most challenging and potentially complex. Unless I decide to remake some of the components, it's pretty much ready to be fitted.
• The X and Y axis motor / belt drive housings. In fact, as these were manually machined, I slightly redesigned them and then remade them on The Shiz (plenty of posts on this blog that show that process). Much better final products now. I still need to make the cover for the X axis but that shouldn't be a massive job.

First steps (in the resurrection):

One of the biggest operations on the machine is changing the worn out leadscrews for the new rolled ballscrews on the X and Y axes. That requires the table to be removed so that the yoke (for the ballnuts) can be retrieved. The new ballnuts are slightly larger diameter (40mm) than the old nuts (39.75mm), so will need to be mounted on the faceplate and bored out on the lathe. The process isn't difficult but involves removing quite a few parts:

X axis Power feed (Align AL500X??):

Bearing brackets from X and Y axis:

DRO scale from the X axis

X axis gib strip and lock handles
X and Y axis leadscrews

The main machine table (but not the saddle):

This exposes the yoke and the various lube pipes:

After removing the backlash adjustment screw, the Y axis nuts can be drifted out. Originally these nuts were a single part but a few years ago I separated them by parting off in the lathe. That left a gap of about 3mm between the resulting halves. It then becomes possible to control large amounts of backlash by controlling the gap between them using the backlash adjuster screw. They are prevented from rotating by the large key.

That just leaves the yoke to be unbolted and lifted out. The lube pipes simply push into the holes in the yoke.

Here it is finally:

It's a bit of a bugger that the bore is so close to 40mm - but not quite. The ballnuts are exactly 40mm diam.

Took almost exactly an hour. The biggest challenge was sliding the table out to the left, as my engine crane has wheels, not castors on its legs and there was limited space. Anyway - job done. 

Next:

• Mount the yoke on the lathe faceplate and prepare to bore it out to take the ballnuts. The new ballnuts are 40mm dia and as can be seen, the yoke bores are around 39.7mm dia. Strange dimension, given that these machines are metric in many places and even if this dimension were imperial, it's different to the classical US dimension as far as I'm aware.. 
• Add some fixing holes to secure the ballnut flanges to the yoke. The current holes are for the original leadscrew nuts, each with a backlash adjuster screw and 2 lock screws. Obviously they are in the wrong position for the flange fixings.