The obscure title relates to a sliding microscope mount which I had just finished – or so I thought.

The chunk thing on the right is a cheap (ish) but surprisingly good trinocular microsocope. the basic idea is that I can move it in and out of my watch-repair (well so far, watch destruction) box as I need it.

The block in the middle at the top of the bar allows for sliding the scope in and out (left and right), rotate the whole thing around the vertical and move it up and down to get the microscope in focus range. there's a clamp underneath to se the height.

Smugly, I took this picture and then decided to take the microscope assembly off and fit the thrust bearing that is intended to reduce wear….

The result was not all I'd hoped.

Sadly, the above picture is not prior to assembly, but after self-disassembly.

I didn't have any stock big enough for what I suppose is the central bearing, So I glued (loctite 638) 3 bits of aluminium bar I did have as you can see above then bored (the two horizontal holes on the mill and the cross hole on the lathe). The horizontal holes are 28mm with 25mm internal bore slide bearings inside (2 each tube). The cross hole 40mm to fit a 40mm silver steel bar I had lying around.

The obvious fix is to glue it back together.

However, one of the issues I had with this is that the stainless steel tube is not exactly precision ground. It's neither particularly straight nor particularly regular in diameter (variation of 2 -3 thou and generally oversized) along the individual 500mm lengths.

It took several goes on the lathe with some emery to get the assembly close to running smoothly. Hampered by the tubes being longer than my lathe bed.

So my first worry is that if I don't get it perfectly aligned when I refabricated it, then the moderate stickiness at some points in the travel will become complete blockers.

The cross hole is arguably worse. The tolerance here is less important, but there is clearly insufficient meat for the glue (each land is about 4 – 5 mm wide I think). I would plan to put a bolt through the centre between the horizontal bores, but harder to see how to do it for the cross bore.

Finally, I was clearly not paying attention to tolerances which I designed this. I assumed that a 25mm tube was, in fact, 25mm and straight. Clearly not, so I wonder if I should re-build the slider unit. Buy a big piece of ally (or steel) Forget the bearings and bore the horizontal holes a with a bit of windage so the steel tubes are a (very) free running fit.

MY concern here is that metal on metal isn't ideal (say stainless on aluminium or steel), but on the other hand, the slides will likely be used a few times a day and I expect would see my days out without getting to the point.

Any advice or suggestions would be most welcome!

Iain