On Sat, 29 Aug 2020 14:45:45 +0100, ss wrote:

The threaded screw turns and moves the smaller metal part along the 2
rods. The 2 rods should just push out and locked with grub screws, so in
theory tapping at the green arrows should push out the 2 metal slides.

Well the arrow heads aren't on the ends of the rods...

WD40 isn't very good, Plusgas is in a different league. Squirt all
the joints with Plusgas and go a way for a day or two (or diesel or
ATF).

Then tap the rods alternatly and from either end with something that
ensures all the impact hits the rod only. Thinking that you may be
able to free up the much smaller areas between rods and main casting
than the rods and cross slide.

What would drive the main screw? Can you get at that and perhaps free
that off an use it to stress either it to rods joint or rods to main
casting by jaming it somehow?

--
Cheers
Dave.