On 09/04/2019 21:38, Chris Green wrote:
I need to fit two chunks of wooden worktop together with their grain
running at right angles. I know I *could* run the join at 45 degrees
but that involves all sorts of other problems and compromises.

So, do I need to allow the joint to move to allow for differential
expansion along and across the grain? It'll be in a fairly low
humidity environment but the temperature is likely to fluctuate quite
a lot (basically in line with outside temperature).

It's oak if that makes any difference.

the joint needs to be allowed to move. that means no glue or firm fixing
in more than one place and the rest of the joint allowed to slide.
Screws or dowels in slots are often used.
the joint needs to be near perfect because any filler will fail.