Add Slots and Tabs to Your Boxes in FreeCAD

FreeCAD is a fairly sophisticated, open-source, parametric 3D modeler. The open-source part means that you can bend it to your will. [Alexandre] is working on a module that lets him easily add tabs, finger joints, and t-slots to models (YouTube link, embedded down under).

Right now the plugin is still experimental, but it looks usable. In the video demo, [Alexandre] builds up a simple box, and then adds all manner of physical connective pieces to it. You’ll note that the tabs look like they’re pieces added on to the main face — that’s because they are! He then exports the outlines to SVG and erases the lines that separate the tabs from the sides, and hands these files off to his laser cutter. Voilà! A perfect tab-and-t-slot box, with only a little bit of hand-work. ([Alexandre] mentions that it’s all still very experimental and that you should check out your design before sending it to the laser.)

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Laser Cut Miter Joints

polyhedraEvery project deserves its own laser cut enclosure, of course, but the most common method of joinery – an overabundance of mortises and tenons, and if you’re lucky, a bit of kerf bending – is a little unsightly. Until tastes in industrial design change to accommodate this simple but primitive method of joining two laser cut panels together at an angle takes hold, the search will continue for a better way to cut acrylic and plywood on a laser cutter. The folks at Just Add Sharks might have a solution to this problem, though: miter joints with a laser cutter.

Instead of the slots and tabs of the usual method of constructing laser cut enclosures, miter joints produce a nearly seamless method of joining two perpendicular panels. The key, of course, is cutting a 45° bevel at the joint and gluing or fastening the pieces together. Just Add Sharks is doing this with a laser cut jig that holds a plywood or acrylic piece at a 45° angle to the laser beam. Yes, it’s only one cut per pass, but after adjusting the depth of cut to 1.4 times the thickness of the material, miter joints are easy.

Using a laser for miter joints isn’t limited to 45°, either. There are a few examples of an octahedron and icosahedron. Of course fastening these mitered panels together will be a challenge, but that’s what clamps and glue are for.

Foot-powered lathe is a tour de force of joinery techniques


Meet [Quetico Chris]. He’s a master woodworker who likes to find his own alternatives to using power tools. Most recently, he was inspired by a fly-wheel from an old factory. He used it to build this foot powered wood lathe.

It works something like a foot powered sewing machine. There’s a lever for your foot which converts the downward force from your foot into a rotating force which drives the work piece. The mechanics of the lathe are pretty common, but we think the build techniques he uses are anything but. The video after the break shows each step [Chris] went through when crafting the human-power tool. His approach was to use wood as often as possible which includes foregoing modern fasteners for older joinery. He uses mortise and tenon, wood pinning, doweling, and a lot of puzzle-like tricks to get the job done.

We lack the skill and tools to replicate this kind of craftsmanship. We’re going to stick to letting a laser cutter form our wood connections.

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Joinery sure to be useful on your next sheet goods enclosure

It’s hard to be an expert at everything, but this collection of wood joinery techniques will make your next project look like you’ve just finished your degree in mechanical engineering. They’re targeted for use in projects where thin sheets of plywood are CNC cut to make enclosures and parts. [Sean Ragan] mentions that these are not new, but we haven’t come across such a large collection of examples as this.

The joints shown above address a series of different needs. You’re probably already familiar with the joint on the bottom right which makes nice corners for a box, providing a lot of surface area for gluing. But just above that is a simple variation on the idea which includes slots for square nuts. This type of mechanical fastener brings strength while keeping the option to take the joint apart again

To the top left you can see a design that includes a snap lock. As the two pieces are slotted together, the barbs flex until they find their mating openings and hold the pieces firmly together. Below that are some bulbed finger joints which don’t need glue to hold themselves together.

[Sean’s] post goes on and on with these designs. He even covers the laser-cut bendable hinges which we are quite fond of.