Having been stumped in my previous post, I asked the question on the Scalefour Society Forum. Almost immediately I received a couple of very helpful replies:
Will L wrote:
It just worked for me. I have this feeling that despite what you said, you haven't followed the instructions... yet. The bit about filing down the back of the cross head in the filing guide provided. Could be that the pin will be a lot thinner when you've filed the cross head down to the correct thickness.
What Will said. My Neilson had no problems either. Have you had a look at the crosshead from the end to see if the pin is a bit mushroomed? Filing down could be the cure, failing that I'm sure Chris could furnish another casting if you asked nicely
Well, no matter what Will (or my manager at work) may think about my ability to follow instructions, I had indeed been following the instructions... Not that it is a chore, with instructions of the quality of Chris's.
I had put both of the crossheads into the filing jig to reduce the depth of them. This is yet another bit of clever High Level design, and you file the thickness of the casting down until it is that same as the slidebars...
However it does indeed appear that I have not quite filed down far enough. When I looked end-on to the casting, as suggested, this is what I saw:
That is literally 0.1mm of metal remaining as a "cap" that made the pin look much thicker than it actually is.
So the instructions are correct, I can carry on, and the Scalefour Society Forum once again proves its value! Thank you gentlemen...