Refitting the modified yoke and ballscrews

First, remove the double ballnut from the Y axis ballscrew, 'cos it's the wrong way round. I've seen ballnut upgrades where the ballnut goes in from behind the yoke but this requires a large slot in the yoke which in return requires a complete new yoke. However you do it, the new ballscrew has to be fed in through the hole in the front with the yoke already in place. I'm sure the supplier would have fitted the ballnut the other way round if I'd asked but having done this before on the Z axis I knew it wasn't a big deal. Having said that, it could go horribly wrong and end up dumping all of the balls on the floor. 

For a 25mm ballscrew, a short length of std 22mm copper (plumbing) pipe is just the right size to slide into the nut, over either of the shoulders that are provided for the main thrust and radial bearings at each end of the leadscrew (housed in those distinctive alloy housings behind the handwheel). You run the pipe tight up against the end of the rolled thread, then unscrew the nut off the ballscrew and onto the pipe. Once it's safely on the pipe, you can use a cable tie or some studding and washers to stop it falling out. Like this:

So this is a good time to check the fit of the ballnut in the bores. Looks good. Y axis:

X axis:

Now to fix the ballnuts to the yoke. I didn't do anything fancy here - just manually drilled and (manually) tapped a couple of M6 holes for the ballnut retaining bolts. Bear in mind that the conventional leadscrew nut is only held by a single 1/4" bolt.

The X axis fixings worked out fine:

And here's the Y axis fixings done:

Time to screw the ballnut back onto the Y axis ballscrew. Tight buttocks time again:

Push the ballscrew through the yoke and slide the ballnut into the yoke, then fit / tighten the retaining bolts using long reach hex driver. It's a piece of piss once you've prepared the way:

Done. And note the lube pipe pushed into the oiler hole in the ballnut (at 10 o'clock). And yes, I checked that the oiler pipes all still work when the table was off.

Now for the X axis ballscrew. I transported it back from Canada in this heavy plastic pipe. It' been in here for about 3 years now....

Very similar lengths and diameters to the std leadscrew but in fact it's slightly different at the left hand end where the servo and pulley will be fitted - I've designed it to accommodate a toothed belt as well as the std handwheel and power feed.

The lube pipe is cut and bent roughly where it needs to be, ready for the X axis ballnut:

At this point I tilted the head so I could get the engine crane in and reposition the machine. It was a bugger to get the table off, so swinging the machine anticlockwise will allow me to get the table back on without killing myself.

Better clean off the remnants of the sealant first while it's on the bench. If you use proper flood coolant, it will piss out between the end of the table and the bracket. (Rant alert). Of course, few people seem to bother with flood coolant these days, preferring to fanny about with those silly mist lube things, or even worse, those daft little brushes to dollop a few drops of oil on the work. Why do they bother? At the best it's lubricating the work but certainly not achieving any cooling as such. Seems to me you either use carbide tooling dry at high speed or use flood coolant with HSS tooling if you want to shift swarf properly. WD40 to stop loominum sticking to uncoated tooling but beyond that? But what would I know. (Rant over)

Up it goes again....

...and back onto the saddle:

The gib strip is refitted, so the table is safe from falling or fracturing the dovetails. Ready to fit the X axis ballscrew now:

As is traditional, I needed to finesse the ballnut a bit at this point, to allow it past the saddle casting. I really don't want any abrasive grit getting in there, so it's done up like a mummy.

That did the trick. Long reach hex driver again and it's in place (lube pipe fitted to oil hole etc):

I still have to refit the Y axis DRO scale and way covers, reposition the machine, retram the head etc. And the X axis leadscrew needs its toothed pulley otherwise the LH handwheel has nothing to tighten up against. Without that, the main thrust bearing has nothing to preload it and there will be about an inch of backlash.

I also specified an M12 x 1.5 thread for the ends of the X axis ballscrew. As that's a metric fine pitch ("normal" metric coarse is 1.75mm pitch), I don't have any suitable nuts, nor a tap to make my own. Had to order one from Cutwel which won't arrive for a day or two. In the meantime if I can find some suitable hex bar I will make up some blank nuts.

That'll do for now.