Chinese machine vise fettling

I bought my 150mm Kurt clone from an outlet in Canada a few years back at a significant reduction during one of those periodic sales. I forget the price but it was pretty darned cheap. You can see a lot of these Chinese products available from different importers / retailers at varying prices and you expect that the quality control will be somewhat variable. Sure enough, this is no exception to the rule.

After machining the X and Y housings, The Shiz was stacked high with swarf. I've decided to remove the machine guards to improve access and lower the machine vise by removing the raiser blocks. They were only added to raise the vise / lower the table so that the console and head don't foul the guards. As I'm not impressed with the guards (much of the swarf and coolant seem to end up on the floor), it seems rather silly to compromise on rigidity and accessibility. And this was a good time for a cleaning session. 

Not sure how it happened but before I knew it, I'd loosened off the leadscrew retaining collar. This allowed the thrust bearing balls to fall out which wasn't something I'd expected. The pressed steel cage that would normally retain the balls had come apart, allowing all 16 balls to fall out into the swarf below. 

To remove the leadscrew and nut you need to remove the fixed jaws, so this pretty much required a full strip down. And in return of course this required me to check out the nut and its sliding contacts. I'm not about to make a silk purse from this pig's ear but there are a few issues to address before putting it all back together:

• The bearing races are completely buggered (distorted). Made of some form of unhardened Chinesium that hasn't reacted well to the clamping forces in this application.

• The surface on the moving jaw where it contacts the flat face of the "spherical" seating in the travelling nut needs to be finished off to a sensibly flat finish.
• The "spherical", self-aligning(?) seating itself looks as if it has been made from a bit of rebar, chewed to shape by some talentless metal eating beaver. The astounding surface finish is just about visible in the above picture.
• The underside surfaces of the slideways haven't been machined. Or rather, the part has been put through the machining process but the raw casting didn't extend down far enough to meet the cutter. When these "angle lock" jaws are tightened, the nut pulls the jaws down by acting against this underside face. On mine, the surface is rough cast in places. So it requires a recut.

I ordered a suitable looking thrust ball bearing from ArcEuroTrade ("51105" type ie 25x42x11 for £4.40 plus vat and delivery) which should be with me tomorrow.

I machined the undercut(s) on The Shiz by manually jogging the machine. My first thought was to use a tee slot cutter but as I have only one of these and it only undercuts by 5.5mm or so, I had to use another approach. 

I have a Korloy "KGT" indexable internal grooving tool that is just the ticket. And no, I didn't pay that much for it - I tend to buy stuff from Cutwel when it is on offer, usually at a significant discount. This allowed me to make a full 7mm undercut.

Job done. Required almost 1mm to be removed before I got a consistently machined surface across the full width and of course I had to undercut both sides to ensure they ended up at the same height. As long as the travelling nut is still well enough aligned not to cause a problem, hopefully the design of the angle lock system will take up the movement.

Now to fettle the other stuff in the list while I wait for the bearing. Then back to machining the cover for the X axis bearing.