How Big of a Pilot Hole Should I Drill?

People often don’t realize the importance of drilling a pilot hole in wood. In haste, some woodworkers will just try to use an impact driver to drive in screws in wood without pre-drilling a pilot hole first. This often ends up weakening the integrity of that board. It is essential to drill a pilot hole first unless you want the wood to split. However, at times people often get confused about how big of a hole they should drill. Most of the time the pilot hole is just too big for the screw. They end up with a loose screw or nail that can’t hold weight at all. So if you are wondering how big of a pilot hole should I drill, we got you covered.

As a general rule, you should drill a pilot hole as big as the screw’s body. However, this does not include the size of the threads on the screw. For softwoods, it is best to make the pilot hole slightly smaller than the size of the screw itself. For hardwoods, make the pilot hole as big as the screw. If you are planning on driving nails into wood, then drill the pilot hole slightly smaller than the shank. This goes for both hardwood and softwood.

People often treat wood like any other construction material. Which usually ends up with mistakes on their part. Wood is very simple to work with, but at the same time requires careful actions on your part. Simply by drilling a hole in wood you can end up saving material that otherwise might have gone wasted. Since wood is made up of fibres, which is why most people will tell you not to go against the direction of the grain while working it. The same principle applies when you are trying to push something between the fibres of the wood. So when you are driving in nails or screws without drilling a pilot hole it tears the fibres and your wood might end up splitting.

How to Determine the Size of the Pilot Hole?

Drilling a pilot hole is pretty simple if you know the sizes of the drill bits and the screws or nails you are using. Determining the size is very important as it will help you find what should be the size of the pilot hole. You can always mark your drill bits with paper tape to tell you what size they are. This way you will know what size bit you are using. When you are buying nails or screws, you already buy a box for them. They come with the dimensions and size so you don’t need to note that down.

Another thing that will help you determine the size of your pilot hole is the kind of wood you are using. Most people do not care about this as it does not make a huge amount of difference. However, the smallest millimetre of difference counts when it comes to fasteners. For softwood that has soft and not very dense fibres, using a bit slightly smaller than the fastener is the best way to go. However, driving nails and screws in hardwood is different. If you are using hardwood then you need to make sure the pilot hole is the exact size as the fasteners you are using.

Why is the Right Pilot Hole Size Important?

Most people don’t know why it is important to drill the pilot hole in the right size. Some people find that even if the pilot hole is smaller it is all good since the threads of a screw will do the rest of the job. However, what they don’t know is that if the wood fibres are densely packed, even a screw will struggle to drive in. This in turn might weaken the integrity of the board that you are working on.

Drilling a bigger pilot hole is obviously wrong as anyone can tell that the screw will just end up loose. So whether you are joining two pieces of wood or just securing a board, the fastener won’t be able to do a good job at it.

If you are working with soft wood, it is more forgiving and a slightly smaller pilot hole works perfectly fine. Though when it comes to hardwood it is important to drill the pilot hole in the right size. This is because the fibres are tightly packed so it is better to keep the pilot hole as big as the screw. If you drill a smaller pilot hole in hardwood, the fasteners will end up exerting pressure on the fibres. This will in turn weaken the integrity of the wood you are using.

Step-by-Step Guide for Drilling a Pilot Hole

Step 1 – Marking the Pilot Hole

First and foremost you need to mark where you will drill the pilot hole. If you are joining two boards together you need to mark them both. You can do this using any pencil or pen that will help you know where you need to place the edge of the drill bit.

Step 2 – Finding the Right Drill Bit

It is now time to find the drill bit of the right size. The drill bit should be either as big as the screw or nail shank itself or slightly smaller in case you are using a softwood board. Most drill bits are already marked with the size engraved on them. In case it isn’t you should always mark the bit with paper tape with the size written on it. Alternatively, you can write it down where you place the bit after you are done using it.

The box of the screws or nails you are using has the size written on it. Just find the drill bit with the same size as written on the box.

Step 3 – Drilling the Pilot Hole

After you have found the drill bit of the right size, it is time to make the pilot hole. To do so, place the drill perpendicular to the marked area. Once you are sure you are completely perpendicular to the drill, start drilling the pilot hole.

If you are unsure if your drill is perpendicular to the wooden board, you can always find a drill that has a level built into it. With the help of the level in the drill, you can see if you are perfectly perpendicular to the board or not. Also, with practice, you don’t need help from a level. Though it is very important that the drill is placed perpendicular to the board otherwise you will end up drilling at an angle.

Another important thing is that you shouldn’t drill too deep into the board. Knowing when to stop drilling is equally important as choosing the right size bit for the pilot hole. If your pilot hole is too deep it won’t sit in as well. You need to drill as deep as the length of the fastener. If you can’t tell how much is that, you can mark the drill bit with a marker and stop when you reach the mark. You can also use a stopper or just mark the drill with paper tape as well.

Bonus Tips for Drilling a Perfect Pilot Hole

  • Use a flat board to place the drill perpendicular to the board: If you don’t have a drill with a built-in level in it, you can always use a flat-edged board or block of scrap wood to make sure that the drill is perpendicular to the board you are drilling in a pilot hole.
  • Mark the drill bit with tape as a depth stop: If you don’t have a depth stop for your drill, you can either mark the drill bit where you have to stop with a permanent marker or tape. Marking with tape is better than using ink as the tape will stop the drill from going deeper. With marker ink, you will have to stop by yourself and there are chances you accidentally might over-drill.
  • Carve the pilot hole for perfect drilling: If your drill ends up fidgeting when you are drilling the pilot hole, just carve it slightly so the edge of the bit sits right in and does not fidget or move when you start. You can do that with the drill as well by holding it at an angle much more convenient to control after which you stop and then place it perpendicular and start drilling.

FAQs – Frequently Asked Questions

What happens if my pilot hole is too small?

If you are drilling a pilot hole in softwood and it is too small then there are chances it will work out just fine. For hardwood, however, it might cause the wood to split.

Do you need a pilot hole for deck screws?

Yes, you need to drill a pilot hole for deck screws as well.

Should I drill pilot holes in a stud?

Yes, when driving screws in a wall stud, you need to drill a pilot hole in it.

Is there a difference between drilling a pilot hole for a nail and a screw?

For a screw, the drill bit needs to be as big as its body, while for a nail the drill bit should be slightly smaller than the shank. A nail and a screw both are different types of fasteners. So they both need a different-size pilot hole as well.

How deep should I drill the pilot hole?

The pilot hole should be as deep as the fastener. If you can’t determine where to stop drilling the pilot hole, then using a drill stop should help you out.

How to make a pilot hole without a power drill?

It is not possible to make a pilot hole without a power drill. However, in cases where the screw is thin and small in size, you can hammer a nail of a slightly smaller size than the screw in the board. Then you need to pull out the nail and use a manual screwdriver to drive in the screw in the board.

What drill bit to choose if you don’t have one that is the size of the screw’s body to make a pilot hole?

In case you don’t own a drill bit that is the exact same size as the body of the screw, then it is a general rule to use one that is slightly smaller than it. Don’t use a slightly bigger drill bit instead go for the one that is closest to it but smaller in size.

Final Thoughts

Driving in screws without drilling a pilot hole can be a recipe for disaster for wooden boards. However, drilling the pilot hole of the right size is also important. Though even in that case, a smaller pilot hole is better than ending up with one that is bigger than the screw. Since you can always widen the pilot hole using a slightly bigger drill bit afterward if it’s small, it can’t go the other way around. So always choose the right drill bit sizes for the screws and nails you are planning to use. If you don’t know the size of the screws and bits, just compare them with your eyes.

Martin Swizz

Hi! This is Martin, I like to research, experiment, and learn new things related to wood carving and other kinds of woodworking.

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