Hi Gary,
I don't turn much Koa, but have used a board or two of it before. As I
recall its kind of oily/resinous. Your friend may want to wipe the surface
to be glued with denatured alcohol or some other agent to reduce the natural
oils on the surface. This should hopefully help the bonding process. Like
any gluing procedure, too much glue and the bond is weak, not enough glue
and the joint is starved. Take a close look at the seperation to see if
there was a enough even glue coverage or if there was too much glue or not
enough glue at all.
When using the CA, don't use too much activator, as this too can weaken
the bonding strength of the glue joint.
To increase the strength of the glue joint, a good method would be to
turn a recess in the work piece and a mating tenon on the scrap block.
Doesn't have to be very deep, but it will greatly increase the strength of
the glue joint. They do however have to match up in order to be most
effective.
Hope this helps.
--Jim M.