I'm new to woodworking and my first large project is an arts and crafts bookcase with keyed mortises for the bottom and top shelf. Its coming along okay, slowly but no big mistakes yet. I'm doing everything through my university's craft center. i started using a mortiser but the bits were worn and burnt- tore up my wood. so since I only have 8 mortises I decided to finish them by hand. The wood is red oak 3/4" thick. The problem I'm having is the chisel is splitting the oak when it reaches the other side of the mortise. (I started each mortise with drill holes) Is the best way to avoid this is to gouge both sides of the board where the mortise should be, either with shallow chisel marks or with a marking knife. Will this prevent chipping on the back side of the mortise. In other words does one have to work from both sides of a board rather than from just one side to avoid chipping? How do most people deal with chiseling out mortises and potential chips along the edge?