Hi Joe (Devmonkey)
Hi All

Firstly I am assuming profiled rails are being used not round rail for high accuracy, repeatability and negligible backlash.

Lateral adjustment of rails is difficult, particularly when you take into account the small amount of adjustment allowed by the clearance around the mounting screw in the bored hole in the linear rails. for type 25 rails typically a 6mm hole and a 5mm machine screw. This only allows +- 0.5 mm of lateral adjustment, and this is if all the mounting holes are perfectly placed. Note in the description the order of processing to minimise chips creeping into the joining surface and lifting the rail.

To solve this problem I devised method where the rails were positioned laterally first using cams. Once this was done I drilled and tapped the mounting holes using an inexpensively built jig. You can make the cams yourself or get them laser cut. You still have to countersink them as detailed in the link.

It is documented here:
https://www.model-engineer.co.uk/for....asp?th=139042

The method worked very well. Alas I have not completed the machine.
I can't wait to get back to it! Alas work has been getting in my way too.

Regards
John