No screw no glue hammer connection

Do you want to connect two pieces of wood together without screws?? This is a laserable wood connection that makes it very easy.

How does it work?

The hammer connection is a type of pin and hole connection, which is secured with a wedge. The unique thing is that the wedge is integrated into the design. The wedge is lasered out with the rest of the joint, held by two tabs (narrow pieces of material). To install the connection, insert the pin through the hole and hit the wedge with a hammer. The wedge breaks loose and pushes the pin apart, which wedges itself into the hole. And Voilá, a strong connection.

Benefits

The interesting thing about this connection is how easy it is to put together. You're done with one blow of the hammer. And you only have two parts to hold.

Then there are no more protruding parts, which is pleasant to use and looks good. If you want to finish your product completely neatly, you can design the pen in such a way that it protrudes approximately 0.2mm. You can easily sand off this top so that you no longer see lasered edges.

A big advantage is of course that you can easily have the connection lasered. Once you get the design right (which you can download below) then replicating it is a piece of cake.

Last but not least: you don't need any screws or glue. That saves money and effort. But above all, I think it gives elegance to have a design in one singular material that can be made in one production step. 

Disadvantages

Of course, as with all connection methods, there are drawbacks to consider.

Firstly; this is a connection that you will never be able to separate. Once fixed, it's fixed. 

Another consideration is how much material you lose at the expense of the protruding wedges. It may turn out that you need more sheet material. If this is a limitation, you can still consider lasering the wedges loose so that you can nest the parts of your design closer together.

Suitable materials

As mentioned earlier, plywood is an excellent choice for this connection. The clamping force is strongest with harder wood types such as birch plywood. MDF  also works well.

A thickness of 6mm or more is ideal. Thinner plates can be used, but will logically produce less strong connections. Bamboo is a special case. Although bamboo is a hard and tough type of wood, it breaks easily along the grain. If you decide to use bamboo, pay attention to the grain direction and make sure the clamping force is parallel to the grain and not perpendicular to it. Although HDPE and POM are possible candidates, they are quite slippery materials, which will reduce the strength of the connection somewhat. For these materials it is better to design a positive-fitting variant of this hammer connection (see below). Acrylate is a less good choice for this connection. Although you can get hammer joints to work in acrylic (see below), it is not as reliable. Acrylic is a brittle material and is sensitive to cracks and fractures in tense places. So there is a good chance that something will break while you drive in the wedge.

Possible applications

As mentioned, this connection is ideal if you have to make many pieces of something, because it is easy to assemble and you save on mounting materials. 

But you can also use it for small tables, cupboards, crates, sculptures and so on.

As an example, we designed a small side table.Ideal for putting up a plant, for example. This design is for 9mm birch plywood. It consists of two legs that you slide together and a table top that you secure with four hammer connections. 

Future improvements

The current hammer connection works with clamping force to hold the plates in place. This is also called a force-locked connection. 

For soft materials, smooth materials or materials that cannot withstand tension, you could also make a form-fitting connection. For example, you can make the pen a little longer and add some kind of brackets on both sides. These hooks are pushed out by the wedge and close around the surface. Such a connection requires little or no force and can still be a reliable connection.

You could also make smaller and larger versions. The hammer connection is now 20mm wide. It can be adjusted to different material thicknesses, but the width remains the same. If you want to adjust the width you will also need to make adjustments to the depth and the flexible parts of the pins to ensure the correct clamping force. 

Downloads

Is this something you could use in your projects?? That's possible! Below you will find drawings of the connection for different thicknesses, plus a parametric version that you can dimension yourself. You will also find the side table. 

The Hammer Joint may be used freely! Here you will find all drawings:

• Hammer joint for 3mm, 4mm, 5mm, 6mm, 9mm, 10mm and 12mm (2d vector pdf)

• Hammer joint for 6mm (3d step file)

• Hammer joint parametric (link to Onshape model)

The sample design (side table):

• Side table 9mm birch (2d pdf)

• Side table 9mm birch (link to Onshape model)

Tips for using the hammer joint

It is important that you use the correct version of the hammer joint as the design is different for each thickness of material. Although the drawings below have been extensively tested, you may need to adjust the drawings slightly for your specific laser, material or design. 

If you want to use the connection in your own design, you will need to paste it in different places in your design. How exactly you do this depends on your drawing program and experience. A 2D CAD program such as AutoCAD or Rhinoceros3D is ideal for this, but it also works well in other software such as Illustrator, Inkscape or CorelDRAW.

For reference, this is my process for designing something with this connection:

1. I make a 3D design of my project in Onshape where I draw simple blocks where I want the connection. Not the real connection, because that is too much work. 

2. I use the AutoLayout  function to lay all the parts flat, and then create an assembly and drawing with all the parts.

3. I download the drawing as a PDF and import it intoRhino

4. In the hammer joint design in Onshape, I set the thickness of the material I will use.

5. I download the 2D files of the hammer connection.

6. In Rhino I copy the mortise and tenon to all places where it is used.

7. Then I export the 2D drawing for laser cutting.

Use the Hammer Joint parametric model in Onshape

View a screencast of exporting from Onshape

I already mentioned Onshape. This is 3D CAD software that runs completely in your browser and therefore does not require you to install anything. It is similar in use to Fusion360 or SolidWorks, for example. Onshape is free to use as long as you don't mind your designs being publicly accessible. You must create an account to gain access. I have created a public document with the Hammer connection. You can find it here: Hammer joint Onshape model Click on the link to view it in 3D. If you want to adjust the settings (parameters) of the model for a different material thickness, you must create an Onshape account . You can then clone the model so that it appears in your own account. Then you can adjust anything you want. 

Adjust the parameters

In the Feature list (left) you see three variables (with the x icon):

• tenon-sheet-thickness

• mortise-sheet-thickness

• laser notch

Double-click it, enter a new value and click the check mark to save. Tip: Have you seen the folder "do not change"? It contains even more variables that, among other things, determine the width of the connection. Only adjust them if you are willing to do some serious testing and experimentation, as they have a major impact on the flexibility of the pin and the clamping force.

Export to PDF

Once you're happy with your settings, you'll probably want to download a 2D drawing to paste into your own design. To export both parts of the hammer joint in one PDF, do the following:

1. Click on the "Drawing 1" tab in the bottom bar.

2. Click the yellow update button in the menu bar to update the drawing.

3. Click the hamburger menu and choose Print. This will open a new tab with the PDF file, which you can then save.

Export to DXF/DWG

You can also export directly to dxf/dwg.

1. Return to the Part studio by clicking on the "fox wedge joint" tab at the bottom of the screen

2. Right-click on one of the items and choose "Export as DXF/DWG....".

3. Choose the desired format in the popup and click Export

Finally

What are you going to make with the hammer connection? We would love to hear or see it! Disclaimer: Although we have extensively tested the hammer connection, we cannot guarantee that it will work for you, in you application also works well. This work is intended as inspiration and as a starting point for your own designs. Good luck!