When Should I Pre-Drill Holes in Wood?

Should we pre-drill wood holes or not pre-drill – that is the question. And this is a really good question because there are times we could or should pre-drill, and there are times where we definitely do NOT want to pre-drill.

What is pre-drilling?

Pre-drilling means that you use a drill and a wood drill bit to drill a hole that is 1-2 sizes smaller than the fastener you are going to use in the wood. For example, if you’re going to use a 3/8″ screw, you would pre-drill a 1/4″ hole about 3/4 the length of the final screw depth in the anchor piece (the anchor wood or the piece of wood where the bottom of the screw will be placed into). The purpose of pre-drilling is to make a hole in the wood that allows for the fastener to still have a good grip but yet it does not require the fastener to do all the work because part of the hole has already been made.

There are discussions on the Internet regarding the topic of whether you should pre-drill wood or not. Most woodworkers agree that there certainly are times when pre-drilling is helpful to applying a particular fastener to hold 2 pieces of wood together, and many woodworkers also agree that the case for pre-drilling screw holes makes more sense than pre-drilling nail holes. However, the agreement pretty much ends there.

The Argument FOR Pre-Drilling

1. It helps keep the wood from splitting
2. It helps the fastener go in to the wood more smoothly – this is helpful especially for hard woods
3. It could provide a cleaner look for the fastener, especially when a counter-sink is used that provides a place for the head of the fastener somewhat below the surface of the wood. This can also allow for a cover or even a filler to be placed above the fastener which will completely hide the fastener from view.

The Argument AGAINST Pre-Drilling:

1. Many type of fasteners will never hold properly from pre-drilling. This potentially includes nails (depending on the kind) that are hammered into the wood and nail-gun nails.
2. Care must be taken when pre-drilling that you don’t accidentally completely pierce the wood on the opposite side of the hole you’re drilling.
3. If you accidentally use too big of a bit, the fastener won’t hold properly and you’ll have defeated the purpose of using a fastener. Fortunately you could fill the hole with a sawdust/glue mixture, let it dry and try again. This should hold up.
4. If you accidentally drill at the wrong angle your fastener will also enter the hole at the wrong angle. Just be aware of this issue when pre-drilling.

When Could You Probably Consider Pre-Drilling Holes?

1. When using screws for fasteners, especially as they get closer to the end of a board. The closer to the end of the board, the more likelihood of splitting when using screws.
2. When using nails for finer projects in hard wood (especially). Finer projects could include thin molding or applications where thin molding could be used such as in picture frames.
3. Any other time when using screws or nails (but not from a nail-gun) where there is a perceived threat of a board split or where you’re interested in hiding the head of the screw or nail using counter-sinking techniques.

Other Ideas and Conclusion

Other suggestions for preventing wood splitting, especially in hardwood (because softwood has more ‘give’ to it) include blunting the end of nails before nailing them into the wood (without pre-drilling) and wetting the nail with saliva to help lubricate the nail.

In the end, take whatever advice makes sense to you here and do your own experimentation. You’ll come up with your own methods and guidelines, and then you can share them with the next generation of new woodworkers!