Why does pre-drilling a hole reduce the chances that wood will split when you put a screw in? Doesn’t the wood still need to expand the same amount?

Question

Why does pre-drilling a hole reduce the chances that wood will split when you put a screw in? Doesn’t the wood still need to expand the same amount?

In: 5

Answer 1

The amount of wood that gets “removed by drilling” is an amount of wood that no longer needs to be “pushed out of the way” when the screw is driven into the wood.

Consider what happens when you pre-drill a teeny-tiny pinhole of a hole, versus a hole slightly-smaller than the shaft of the screw, versus a hole equal to the size of the screw’s shaft. As the holes get bigger, the screws get easier to drive with less and less effort.