Ballscrew machining and pulley spacer / locknut

Let's get busy machining stuff: 

Here's what I need the ballscrew to look like:

So firstly, chop off the excess length and face off / turn down. 

Both ends done - coupling at one end, bearing and pulley at the other

Now make up a locknut with M10 x 1.0 thread. I have some nice 1" bronze, so why not use it? Nice to machine and very colourful!

The tap is clearly nice and sharp....

Nearly done. I need to drill a couple of holes in the nut so I can use circlip pliers to tighten it. I'll do that in the mill later when it's next in use.

So that's the ballscrew pretty much ready to slot in. I'm thinking that I will drive the ballscrew via the coupling with a piece of 8mm rod initially, to avoid having to butcher the original leadscrew until it's absolutely necessary - or even at all. Something to think about....

Machining the underside of the cross slide body:

Let's prepare for machining the underside of the cross slide now. I'm almost at the point of replacing the leadscrew with the ballnut but first I have a few mm to remove from the underside of the cross slide, to make room for the ballnut yoke, the encoder read head and the limit switches. Also, I need to machine the fixing holes for the ballnut yoke (M5 clear, with plenty of rattle). Although it would still be possible to use the original leadscrew and nut at that point, I'd need to pack the nut out to do so. 

Let's double check the dimensions, particularly the required height of the underside relative to the ballscrew centreline. If I got this wrong, the ballnut won't be at the correct height for the ballscrew and I'd have to bugger about with packing or machine some more off the yoke, depending which way I erred.

Design height:

In Fusion, I see the centre height of the ballscrew above the slide surface of 6.36mm.

Measuring with my cheapie digital calipers, I see 6.45mm, with >20-30um tolerance. Given that I have designed the rear bracket to have the best part of 1mm adjustment at the fixings, that looks pretty safe.

Now I need top check the ballnut yoke height vs the dovetails in the cross slide body.

Ooops-ette. The yoke is 19.2mm, not 19.06mm. It's currently 0.14mm too tall. Looks OK, although not 100% as planned - presumably due to manual measurements way back when. I can easily accommodate that in the bracket adjustment. 

The channel is 25.4mm (1") wide and the ballnut yoke is 28.5mm wide, so I need to machine a shoulder on each side, of 1.55mm width with enough depth to clear the adjacent lands ie ~1.5mm. That's a pretty trivial mod and means I can refit the original leadscrew nut at a later date without messing about - there's no point of no return.

So:

• Machine shoulders at either side of the yoke: >1.5mm depth, leaving 25.4mm width.
• Machine the underside of the cross slide body.
• Drill and counterbore the yoke fixing holes. These are now M5 fixings - originally showed M4 which are a bit spindly, yet there's room for larger jobbies.

Sacrilege time:

This is a lot less significant as surgery goes, compared to the butchery I perpetrated on the saddle. 

Pleasingly, Tim Paterson's post processor add-in worked splendidly and although there was no tool change, it handled the replacement of the rapid feeds nicely.

Slight problem-ette, though. Half way through the operation (one side done), the machine stopped and refused to resume, claiming an e-stop situation. Bugger. At least it simply came to a halt with no harm done.

In fact, with the table in the middle of its envelope and the actual e-stop clearly not depressed, there wasn't a "real" e-stop at all. But on this machine the limit switches are on the same input as the e-stop, so more likely was that they were the root cause. Annoyingly, I'd forgotten to tell the tool library that the BAP300 tool would be cutting dry, so the coolant came on and the tap wouldn't completely stop the flow. The Y axis limit / home switch assembly is in this little box under the saddle and sure enough, when I loosened the screws on the cover, it was clearly full of coolant.

It's obviously getting in through the top. I'd seen previously that it was full of neat oil but couldn't tell if that was coolant or lubricant, not least because the previous owner had only ever used neat oil.

Anyway, dried it out and machined a slot in the cover to enable the egress of any further further ingress.

And back into action. Finally for the cross slide, I needed to counterbore the yoke fixings:

Job done for the cross slide body. Now let's see how it goes together....