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

A wood-screw is pretty much a self-propelled nail. The long central spike is solid, and that is the width and depth of the hole you drill.

The outer thread part is mainly fresh air — the actual screw part is quite thin and only takes up about 20% of the space, and has a sharp edge. So it just cuts a helix for itself as it goes in, and squeezes the wood a little.