well, further to what I posted before, this is the first look at the sort of thing being made. This was a simple test conducted at the workshop to see what the machinist could make.
It turns out that they're pretty good
They can get the channels very thin, about 1mm, and the spaces between the channels about 1mm, and quite deep too.
The real thing should be done by next weekend. The final design is the same outside circle width, but has 3 more channels than this test.
It'll also obviously have the o-ring and tapped holes ( cheers to everyone who helped with that bit )
What do you reckon? Small isn't it.