i have almost completed a 4 shaft counterbalance loom.
i have two metric reeds One says M 40, the other says 10.
Any suggestions about nail spacing for my raddle?
If you want to work with metric measurements, make the raddle with 1cm spaces. If you want to work with inches, make them 1/2 inch. The size of your reed does not have to coordinate with the raddle. A metric 40/10 is almost equivalent to a 10 in inches. For a list of reeds with equivalents metric and inch sizes, there is a chart in my book, Learning to warp your loom.
Joanne is right, the number of threads in one space in your raddle and the size of that space don't have anything to do with your reeds. You need to figure (based on the size of your warp and the ends/inch that you want) how many threads you want in a raddle space (mine is 1/2 inch). If I want 24 epi, I want 12 threads per raddle group. How I thread the reed to achieve 24 epi depends on the reed that I am using.