Dowel joinery is great – strong and easy to do.
I didn’t have a dowel jig in my workshop, so I decided to make one – a self centering doweling jig.
Usually, you want to use a dowelling jig when it comes to connecting two planks with dowels.
By using a self-centering dowel jig, you can drill the holes exactly opposite each other, resulting in a connection that makes a perfect fit.
I made this centering jig with wood leftovers, 2 brackets, and a few bolts. It can be adjusted to different thicknesses and easily clamped down to a workbench. This jig is built for 6mm drill bits but it can be made in the same way for 8/10 mm drill bits.
This is a fairly simple and quick project and it will help out when it comes to connecting wood pieces and using dowels in your projects.
With the instructions in this blog post, you will learn step-by-step how to make a dowel jig.
I hope you enjoy it!
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Table of Contents
- Self-centering doweling jig plans
- Related Questions
- How To Make a Self Centering Dowel Jig
- Attaching Brackets to the base
- Insert Spacers for the dowel
- Assembling and Adjusting the Dowel Jig
- How to use a Self Centering Dowel Jig
- Edge Joints
- Should I make dowels?
- Self-Centering Dowel Jig Video
- Jigs used for the project
*Safety is your responsibility. Make sure you know what you’re doing and take all necessary safety precautions while working with power tools. Safety comes first!
Always be cautious and careful when using any power tool.
What you'll need to build the Self Centering Dowel Jig
Self Centering Doweling Jig
2x Spruce wood (planed, preferably square) – (15 x 2,8 x 1,2 cm)
1x Spruce wood (planed, preferably square) (15 x 2,8 x 1,8 cm)
2x Brackets – (14 x 1,5 x 2 cm) – each with 3 predrilled holes preferably
4x Wood Screws – 3 x 20 mm
2x Wood Screws – 3 x 12 mm
Round hollow aluminum spacers
diameter inner ø6mm, outer ø8mm – 1,8 cm
Hand Drill, ø6mm Drill Bit (better for metal)
Wood Glue / Epoxy
How to adjust a self centering dowel jig?
The principle is quite simple. A self-centering doweling jig self-centers itself around the workpiece using two parallel guide rails. The main piece has metal bushings into which drill bits are inserted. The bushings are located exactly in the middle of the axis of the main piece ensuring that the drilled holes are always centered. They also make sure the holes are drilled precisely vertically. To ensure accurate and uniform borehole depth it is good to use a drill bit stop collar.
- Mark the position of the dowels and the center between the dowels on the workpiece.
- Place the self-centering dowel jig around the workpiece, close the parallel guides, and align it with the centerline.
- Drill the holes
How deep should a dowel hole be?
The ideal depth of a dowel hole is one that exactly accounts for the length of the dowel. The optimal dowel joint precisely encloses the dowel from one end to the other. The longer the dowel, the stronger the joint. Nevertheless, a tiny void of around 2mm is usually left in the hole to catch excess glue or water and prevent dowel hole blowout. The resulting pocket also covers deviations in the length of the dowels.
On the other hand, it is important to realize that any resulting pocket reduces the strength of the dowel joint. In some cases, too much-trapped glue may seep through.
Are dowels supposed to be loose?
A good practice is leaving a tiny void around 2mm in the hole to account for glue and water. The dowel will expand in contact with glue moisture. It will swell and create a good tight fit.
Having a 6mm dowel does not guarantee it would fit into a 6mm hole. There could be two main reasons for that. Every single dowel may have a manufacturing deviation which could be around 0,1mm. The other factor is the material in which the hole is drilled. Materials behave differently. A 6mm hole in plywood will have a different diameter than a 6mm hole in hardwood or other material. Make a fitting test of the dowel before continuing on the workpiece.
The total dimensions of the dowel jig are 15 x 14 cm. After deducting the side guides that leaves room for up to an 11cm wide workpiece to be fit in the doweling jig.
How To Make a Self Centering Doweling Jig
Step 1: Build the Parallel Guides
Start by measuring and cutting all the wood pieces necessary for the jig (see dimensions above). You can easily crosscut the pieces on a Jigsaw Crosscut Jig.
Mark the position of the holes to be drilled on the parallel (side) guides. It is very important and crucial to drill the holes as accurately as possible. This will determine how accurate the doweling jig will be.
You will be able to adjust and fine-tune the jig during the next phase but take extra care when drilling the holes in this step. This step is one of the most important ones when building this self-centering doweling jig. It is worth spending a bit of extra time on this activity.
TIP: To accurately drill a hole in the wood pieces you can first use a marking gauge to mark the center and then a center punch to make an indentation, to allow for the drill to make a hole at the same spot.
Step 2: Attach the Brackets to the Parallel Guides
Before attaching the brackets to the parallel guides, in my case, I needed to make one additional hole in the center of the bracket.
(This might not be necessary for you depending on the type of brackets you use. If you can, preferably get a bracket with three already pre-drilled holes.)
Mark the center of the bracket using a ruler marking gauge and a center punch. Drill a hole in and use a countersink drill bit to fit the screw head in.
Countersink the screws completely so they don’t get in the way when adjusting/setting the dowelling jig.
Screw the brackets to the side guides.
Do not tighten the screws completely. Leave them loose a little bit to let the wooden pieces move to some extent.
The ideal position is to leave just enough space between the screw and the bracket to be able to move the bracket freely, yet still nicely attached to the wood piece, having the screw head countersank.
When you close the dowel jig the wooden pieces should be completely parallel. That depends on how you managed to drill the holes at the beginning.
If the wooden pieces are completely off you should consider making new ones. However, if they are misaligned just a little bit you can sand the wood pieces along the inner side to get a nice parallel fit.
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Step 3: Insert Spacers
Mark the position of the spacers and drill 2 holes. The distance of the holes on this self-centered dowel jig is 4 cm. Make sure you drill the holes on the centerline of the piece.
It is worth using a drill press for drilling the holes or a simple jig that would help you drill the holes vertically without using a drill press. You can find many guides on how to build these DIY jigs and you can build one literally in a few minutes.
I used an ø8mm drill bit to drill the holes. After inserting the aluminum rods, a hole of ø6mm remains for a ø6mm dowel.
In the process, I also created a notch in the middle of the centerpiece (right in the middle between the holes). The notch servers as a “sight hole” that lets you align the dowel jig with the piece you’re drilling, exactly on the spot where you want it.
I used a hand saw for making the notch, no power tools are needed.
Cut the aluminum spacers to size – 1,8 cm – and round the edges a little bit to easily fit them in the drilled holes.
Add wood glue or epoxy and insert them in the holes.
Try not to get glue in the spacers. If that happens clean the insides with a piece of cloth or you can use sandpaper once the glue dries off.
NOTE: I am using aluminum spacers. You might consider using steel spacers, though I don’t think it is necessary.
When drilling holes with the dowel jig I don’t use drill bits for wood but metal. Not only do they spin better/easier in the spacer but they drill holes more accurately not shifting the entire jig.
Step 4: Assemble and Adjust the Dowel Jig
Fix the centerpiece to the parallel guides with screws.
Leave the screws loose first, skew the jig to one side, and align the centerpiece with the side wood pieces.
When all the pieces are completely parallel, fix the screws on the centerpiece tightly.
This is what the finished self-centering doweling jig looks like.
You should end up with all 3 wood pieces running in parallel.
How to use a Self Centering Dowel Jig
You can use a self centering doweling jig to make Edge joints, L-joints, and corner joints.
Edge joints are great when you need to connect two pieces of wood together and make them flush. This is useful, for instance when you want to join 2 boards together.
L- joints are great when you need to connect two strips of wood as an “L”. An L joint comes in handy when joining table legs, picture frames, or box corners.
How to make Edge Joints with a self centering doweling jig
- Mark the center place of the doweling jig on the wood and the locations where you want to drill holes for the dowels.
- Place the dowel jig on the wood piece and align the centerline with the dowel jig notch.
- You can clamp down the jig to a workbench for better stability and accuracy while drilling.
- Set the right depth of the drill bit using a stop collar and drill the holes.
- Glue dowels in one of the wood pieces and check how far they protrude. Shorten them if they protrude too much.
- Glue the wood pieces together.
As mentioned earlier in the blog post I am using drill bits for metal. They seem to work better with the jig and they don’t get stuck in the spacers.
TIP: You can also use sandpaper to sand the inside of the spacer. This will give just enough extra space for the drill bit.
Once finished with the holes glue the dowels in and connect the wood pieces together.
This is how it looks after joining the pieces together. They line up perfectly flush.
How to make L-Joints with a self centering doweling jig
In the same way, as described above, you can join 2 pieces of wood as an “L” – either anywhere on the edge of the wood piece or at the corner.
- Mark the center place for the doweling jig.
- Place the dowel jig on the edge, align the centerline, and lock it.
- Fix the dowel jig in place.
- Set the right depth of the drill bit.
- Glue dowels in one of the wood pieces.
- Glue the wood pieces together.
The doweling jig is great and really helps a lot with the projects. The material is easily available and the total costs are low.
Although it is fairly easy to build this self-centering dowel jig it is necessary to pay attention to some steps in the process since they determine the accuracy of the jig. Specifically when:
- drilling holes in the parallel guides that are connected through brackets
- drilling holes for the aluminum spacers.
These 2 steps need to be as accurate as possible. That could give a bit of a headache. But don’t worry, take your time, and do them as best as possible.
You can also make your own dowels at home. They are fairly easy to make and there are multiple ways how to do it from a simple jig to a lathe. Though I wouldn’t recommend making those at home. Manufactured dowels are much better than homemade dowels. Fluted or spiral, they are stronger and it is easier to glue them. The notches on the dowels will hold just the right amount of glue and the unnecessary excess is pushed out.
So.. Ready to build a self-centering doweling jig now? Let’s do it!
DIY Dowel Jig Video Tutorial
If you want to see how it is done, check out the video below for a step-by-step guide on how to make a simple self-center dowel jig.
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