,Hello Keith,
I do indeed have the book! There has been lots of replies, but only a couple answered the question. To remind people, it was "How do you set up the correct gap for the alloy that you are using" I may well be wrong, but I don't think that even your book addresses the question.
There are lots of references saying what the gap should be, but virtually nothing on how to achieve said gaps. Apart from some information in Alec Farmers book re brazing tubes in the inner firebox plate.
For example I have seen people, including myself, riveting a structure to hold things together during brazing. The gap around the rivet must be close to zero, yet it still seems to solder well.
I must have been very lucky , because I never gave gaps a thought in the past, unless it was subconsciously.and I have never had a major problem.
Regards,
Andrew.