Cross slide assembly completed - pretty much

Nearly there?
Just a couple of things to do, then I've pretty much completed the cross slide assembly:

• Back at the end of December I realised I'd make a rooky mistake with my bearing selection. So instead of needing to accommodate one 6200 bearing, I need room for two 7200B bearings. That means I need to lengthen the 10mm nose of the pulley end of the ballscrew by ~9mm to make room for the second bearing. At least that will almost eliminate any backlash. 
• The driven pulley is slightly too long, so will need to be machined back 2mm or so to clear the cross slide bracket.
• Make a shortened spacer washer between the bearings and the driven ballscrew pulley. I need to ensure there's a gap between the pulley and the cross slide bracket but currently it's rather excessive. It's not sensible to shorten the existing spacer washer as it's only 6mm long. Instead I'll make another one.

Out with the ballscrew. I'm not going to remove the ballnut and risk my balls dropping again, so instead I'll wrap it in some cloth duct tape.

No pictures, but the 4-jaw had enough room to accommodate the ballnut in the bore behind its jaws.

The second bearing is purely in thrust. Once it's been nipped up by the locknut, it doesn't really need any radial support. That may not be entirely approved but I'm buggered if I'm going to remachine the whole bracket from scratch just to extend the bearing bore.

Goes together nicely. There's a bit of residual torque due to the preload of the bearings but that's controlled by Nachi's tolerances. These things are designed to work as a pair. There's no discernible backlash at this stage.

So here's the whole cross slide drive assembly. It simply bolts onto the back of the saddle body using existing 1/4-20 UNC holes and attaches to the bottom of the cross slide. Apart from the double bearing cockup which I can live with, it's come out as I'd planned.

I'll keep it safely wrapped up in a bag to keep dust and grit out until I've made the rest of the components such as the Z axis (longitudinal) drive. Then I'll be able to move to the electrical / configuration part of the project.

Motor pulley change:

When I removed the puny 1.1kW spindle motor and shoehorned in a more interesting 3kW machine, I also ended up with a 1500rpm base speed instead of 3000rpm. As I don't want to lose the higher spindle speeds, I need to do something about that. The pragmatic solution seems to be to fit a larger pulley on the motor. I can't change the driven pulley, as it's integrated with the gearbox and also forms part of the spindle brake. 

I'm limited by space, so the max speed will be a function of how large a pulley diameter I can squeeze in there. Using a cheap ruler and a calibrated eyeball, I've estimated that a 160mm jobbie should just clear the adjacent features with some minor(?) fettling of the brake interlock switch mechanism. The current pulley is 106mm, so this should give me a ~60% speed boost. In conjunction with the VFD, I should be able to recover most of the 1600rpm, possibly a bit more. At the higher speeds, I would be turning smaller diameters, so perhaps this won't be problem. 

The driven pulley seems to be 144mm at the neutral axis and the axis centres around 235 -240 including some adjustment range. What belt length should I require? Looks like an A35 or A36 - ordered one of each at just under £5 each. 

Seems to fit OK and the larger pulley doesn't foul anything, like the cover or brake linkage. Now I just need the belt , refit the brake / switch and we are done. The latter need to be swung out of the way to get the pulley and belt on.