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.
Typically, a dowelling jig is your go-to tool for joining two planks with dowels. With a self-centering dowel jig, you can precisely drill holes that align perfectly opposite each other, ensuring a snug and seamless connection.
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 provided in this blog post, you will learn step-by-step how to make a dowel jig.
DIY Dowel Jig Video
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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Table of Contents
- Self-Centering Dowel Jig Video
- Self-centering doweling jig plans
- Materials and Tools
- 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
- L-Joints
- Should I make dowels?
- 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!
What you'll need to build the DIY Self Centering Dowel Jig
DIY Self-Centering Doweling Jig
2x Spruce wood (planed, preferably square) – (150 x 28 x 12 mm)
1x Spruce wood (planed, preferably square) (150 x 28 x 18 mm)
2x Brackets – (140 x 15 x 20 cm) – each with 3 predrilled holes preferably
4x Wood Screws – 3 x 20 mm
2x Wood Screws – 3 x 12 mm
Screws and other – https://amzn.to/41PodgQ
Check all the Tools I Use
Tools:
Jigsaw – https://amzn.to/3S85cDr
Hand Drill – https://amzn.to/3HqLEnH
One Hand Clamps – https://amzn.to/48jGxkZ
Spring Clamps – https://amzn.to/41Nuh9D
F-Clamps – https://amzn.to/48ArzY1
Tape Measure – https://amzn.to/3TN0SKM
Center Hole Punch – https://amzn.to/48Fq7mv
Hand Saw – https://amzn.to/48if4Qz
Machinist Square / Speed Square
Other
ø6mm Drill Bit (better for metal) –
Wood Glue – https://amzn.to/48ltKhJ
Epoxy – https://amzn.to/3tJ5R4L
Sandpaper Sheets – https://amzn.to/41OMx2p
Wood Screws – https://amzn.to/41PodgQ
Round hollow aluminum spacers
– diameter inner ø6mm, outer ø8mm – 18 mm
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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.
Creating a doweling jig is quite simple. But if you’re looking for a ready-made option from a shop, I’d suggest the following one.
Features an extra-large opening for clamping onto various-sized pieces of wood.
Let's Start
The total dimensions of the dowel jig are 150 x 140 mm. After deducting the side guides that leaves room for up to an 110 mm wide workpiece to be fit in the doweling jig.
How To Make a Self Centering Dowel 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 strips using a Jigsaw Crosscut Jig.
Mark the spots for drilling on the side guides carefully. Accuracy here is key and will greatly influence the precision of your doweling jig.
Although there’s room for adjustment in the next phase, pay special attention to drilling these holes accurately. This is a crucial step in creating a self-centering doweling jig and deserves extra attention and time.
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 make an indent using a center punch. Drill the hole and use a countersink drill bit to fit the screw head in. Make sure the screw head is flush with the surface.
Countersink the screws completely so they don’t get in the way when adjusting/setting the dowelling jig.
Attach the brackets to the side guides with screws, but don’t fully tighten them. Leave them slightly loose to allow the wood pieces a bit of movement.
NOTE: 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.
Ensure the wood pieces are perfectly parallel when the dowel jig is closed, which relies on the precision of your initial drilling.
If the pieces are significantly misaligned, you might need to create new ones. But if the misalignment is minor, simply sand the inner sides of the wood pieces to achieve a smooth, 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 this vertical drill jig and you can build it 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.
During the process, I made a notch in the center of the middle piece, positioned exactly between the holes. This notch acts as a “sight hole,” allowing you to line up the dowel jig precisely with the area you’re drilling into.
I crafted the notch using a hand saw, so there’s no need for power tools.
Cut the aluminum spacers to size – 18 mm – and round the edges a little bit to easily fit them in the drilled holes. Then 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. They not only spin more smoothly within the spacer but also ensure more precise drilling without moving the jig around.
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
A self-centering doweling jig can be used for various types of joints, including edge joints, L-joints, and corner joints like miter joints. Here’s a bit more about each:
Edge Joints: Ideal for connecting two wood pieces side by side to create a flush surface. This type of joint is particularly useful for joining two boards together seamlessly.
L-Joints: Perfect for attaching two strips of wood in an “L” shape. L-joints are useful for assembling table legs, framing pictures, or constructing box corners.
Corner Joints: These include miter joints and are excellent for creating precise corner connections, adding both strength and visual appeal to your projects.
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 (butt joint) of the wood piece or at the corner (miter joint).
- 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.
My Take
A doweling jig is a fantastic tool that significantly aids in woodworking projects. This one is made from readily available materials and is quite affordable.
Building this DIY self-centering dowel jig is relatively straightforward, but it’s crucial to be meticulous during certain steps to ensure the jig’s precision. The accuracy of your work hinges on:
- Drilling holes in the parallel guides that are secured with brackets.
- Making holes for the aluminum spacers.
These steps are essential and require precision to avoid potential issues. However, there’s no need to stress – just take your time and aim for the highest accuracy possible.
While it’s possible to create your dowels at home using various methods, from simple jigs to lathes, I generally advise against it. Commercially produced dowels are superior. Whether fluted or spiral, they’re stronger and easier to apply glue to. The grooves in the dowels help retain the right amount of glue, while excess is effortlessly expelled.
So.. Ready to build a self-centering doweling jig now? Let’s do it!
KEEP READING: Here’s another type of a Dowel Jig you can make – an Adjustable Handheld Dowel Jig
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