I don't think you will find technical data from glue manufacturers that recommends "roughing up" a surface to be glued. A smooth freshly planed or sawn surface is best. Roughing increases the thickness of the glue line and that is generally not a good idea. Lightly scuffing plywood with sandpaper to remove manufacturing residue is the exception. Epoxies tend to forgive us for small transgressions, but why not go with the adhesive manufacturer's recommendations? I wouldn't worry about the sanding of end grain. End grain joints don't have much structural integrity anyway. Gussets and/or blocks secure those joints. Rich Hartwig Waunakee WI
>I can see where the accepted idea of roughing up the wood surface > with coarse sandpaper is a good move because it increases the surface area > for gluing.