When you drill a large hole, sometimes you will find that the backside of the workpiece tend to splinter when completing the hole,especially when you use a large hole saw or spade bit. If the stock teared, you should be careful, because it maybe go into your skin and cause pain and infection.
There are two simple ways to avoid it.
1. Before drill, you can clamp a piece of hardwood behind the word. Do not use anything softer than your workpiece or you might find that a splinter will happen.
2. You can just drill half-way through the stock, until the pilot just penetrate the backside of the work-piece, then the piece over and drill form the other side.