Ultimate Guide to Choosing Dowel Size

Most woodworkers underestimate the strength of a good dowel joint and just prefer screw joints instead. However, dowels are extremely durable and great for heavy-duty furniture. If you are using these for the first time you might have trouble with the right size. The right dowel size will determine whether the joint is going to be strong or not. So let us help you with that with our ultimate guide for choosing dowel size.

Choosing dowel size depends wholly on the thickness of your lumber. When it comes to the length you need to choose the dowel length twice the size of your drill hole. You want an equal length of dowel for the pieces of wood you are connecting. For the diameter, you need to choose one that is half the thickness of the piece of wood itself. Anything bigger will weaken the integrity of the piece as a whole.

In the old days, people used to make furniture by using dowel joinery. People tended to avoid using metal fasteners as they didn’t bring the kind of aesthetics needed in those days. However, screws are very durable and don’t break easily. Not to mention they are very convenient to use when compared to a dowel. So using screws is not looked down upon in woodworking. Though when people try to create a classic design for their furniture they still use dowels when necessary.

How Do I Choose the Right Dowel Size

When it comes to choosing a dowel size you need to consider two things. One is how long the dowel needs to be for the joint. The second thing which is very important is how thick the dowel should be. Dowels come in either the form of a rod or cut-down pins. Dowel rods typically come in 20 cm, 30 cm, and 40 cm lengths. However, dowel pins usually come in either 1-inch or 1-and-a-half-inch sizes.

Choosing the Length of Your Dowel

Since dowel rods come in various sizes and they can be pretty big. One might feel confused as to what length dowel should they choose. Standard dowel pins are usually only found as 1-inch and 1 and a half inches long. This means most people don’t need a bigger size than that.

If you are picking a dowel for a blind hole, then you need to get one twice its size. The usual size of a blind hole in dowel joinery is either 1/2 or 3/4 of an inch. You always need to get a dowel that is going to be twice the length of the actual hole. This will allow equal amounts of dowel length to be inserted in both blind holes of the two pieces that are joining.

If you are choosing a dowel for a through-holes, then it needs to be as long as the length of the lumber itself. Usually, it is one through-hole and one blind hole on the side grain or end grain in this kind of joinery. In this case, you need a dowel as long as the through-hole and the blind hole.

Choosing the Thickness of the Dowel

Choosing a dowel’s thickness is very easy compared to choosing the length. You just need to find a dowel half the thickness of the actual lumber you are going to use in the joinery. If the dowel is thicker it will weaken the overall integrity of the lumber and also the joint itself. The joint will be very weak compared to if you choose a dowel that is only half the length of the wood that you are connecting.

Should The Dowel Be Bigger Than the Hole?

One question often asked by new woodworkers when working on dowel joints is should the dowel be bigger than the hole? This question works two ways, should it be thicker than the hole, or should it be longer than the hole itself. In the above section, we already discussed one of these questions in detail.

As we said earlier, the dowel should be bigger than the length of the hole. It should be at least twice the size since you are using it to join two pieces of wood together. It should fill in both mortises or blind holes/through-holes completely. So you choose the length of the dowel accordingly.

When it comes to the thickness of the dowel according to the hole, then it should be an exact fit. It should be the exact thickness of the drill bit you have used to make the hole. It should not be bigger or thicker otherwise it will not fit inside. You don’t push a dowel in the hole you let it slide inside and fit in.

What if the Dowel Size is Too Big or Small?

If the dowel is too long for the mortise or hole you have made for it, then you can simply see it off. Dowel rods are big in size, you need to cut them to length already. If it is a through-hole then just simply slide the dowel all the way through and then use a planer to square it to the correct size. If it is too big then you can just use a saw and then use a planer or sander to adjust the size.

If it is smaller in size compared to the hole, then you can use a wood filler. A filler will fill in any length the dowel is missing. In a through-hole it will hide the dowel, in a blind hole it will fill in the gaps. However, a wood filler does not add the structural integrity to wood as a proper-sized dowel will. This means the joint will be weaker compared to the one of the proper size.

Recommended Dowels

If you are using dowels in a blind hole then they need to have some grooves in it to help the air escape. This is why the most common type of dowels that people use these days are fluted. They have grooves already made in them which help the air escape from the hole. If you don’t allow the air to escape from the hole and use a dowel that does not have any openings or grooves for that purpose, it will split or crack the wood as the air tries to escape.

When it comes to through holes you can use a normal dowel pin without any grooves in it. This is because the air can pass through the hole and does not get trapped.

These Hardwood Fluted Dowels from Rhino Industries are a great buy, not to mention they are kiln-dried and super durable. You can find dowels from your local home depot with ease too.

Tips and Tricks for Dowel Joinery

  • When making a hole for a dowel, using a jig will make sure you drill straight. You can always use a drill press as well, but if you don’t have one or it is not possible for the project then you will have to work with a jig. You can purchase these jigs or make one for yourself at home.
  • Always use fluted dowels for blind holes. As we talked about briefly earlier, if you use a normal dowel that does not have any openings for the air to escape it can damage the wood, often cracking and splitting it.
  • Cutting a dowel to size is common practice, so if you find the hole to be too small for the dowel then use a saw to cut it. If the hole is not blind but through, you can plane it or sand it if it’s just a little bit bigger than the length of the hole itself.
  • Don’t use too much adhesive in the hole when putting in the dowel. It will stop the dowel from properly fitting in.

Final Thoughts

Going out of your way to use dowels for joining two pieces of wood might feel like a hassle but it is very rewarding once finished. There are no open screw holes visible which give a beautiful aesthetic look to the whole piece. If you were not sure if you should use dowels because you don’t know how to choose the proper size, hope our article helped with that.

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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