I'm having trouble chisling my stop dados. I've cut the dado with a router stopping 3/4 in short and am squaring up the dado with a chisle. What keeps happening is the cross section doesn't cut clean and pulls some of the wood out from under my cut line. As far as I can tell the chisle is sharp. The wood is pine which may be part of the problem. The panel has a equal size rabbet on each end which I'm able to use a knife and am able to avoid the problem. Any advise would be greatly appreciated.