Jointly, the CNC Typeface

Jointly is a typeface designed for CNC cut joinery in wood. For as long as wood has been used as a construction material, there has been joinery. From dowel joints of flat pack furniture, to the half-lap of a log cabin, to the exquisite geometry of Japanese traditional joints, and the ever-classic dovetail, joinery says a lot about an object’s purpose, the craftsperson, and about history. But what if the joints could literally say something? Jointly was designed for messages that last, poetry in wood, and allowing furniture to truly speak for the first time.

One of the major limitations of a rotary type CNC machine like a router or a mill is the radius of the tool. Inherent in any CNC cut is a fillet or curve on every internal corner equal to or greater than the radius of the tool. Additionally areas narrower than the tool diameter cannot be reached. As such, a normal typeface can not be used as a mortice and tenon type joint. The corners, points, serifs and thin section of letter forms can not be cut by a router or mill. In every existing typeface I tested, there were places where either the internal cut or the external cut were not reachable by a rotary tool. JOINTLY was created to solve both of these problems. For a text height of 3/4 of an inch or taller, all internal and external curves have a radius greater than 1/16th of an inch and all spaces inside and outside of letterforms have a width of at least 1/8th. As a result, with a router bit of 1/8th inch diameter, the font can be used to create working joints.

Clearly other fonts can be used to cut text with a CNC machine, but in every other case, this is purely a decorative embellishment. Text is often cut using a v-carving or engraving operation with a pointed tool in order to reach the smaller areas.

For the cutting of the parts, I used a Shopbot router fitted with a custom fixture for holding boards vertically for the tenons and a second router for the horizontal mortise cuts. I have also used the Shaper Origin (hand held CNC router) to cut joinery. This is a much more affordable option and also what we used for my class at Castle Hill Art Center in Truro MA.

For materials, the shelved featured in this Instructable are made of walnut and cherry lumber and glued with Titebond.

A 3/4 inch long 1/8 inch diameter router bit is also required. Up cut or down cut will work, but down in my experience creates a cleaner cut. I acknowledge that these are a bit expensive, but I'd recommend buying at least two. I certainly broke a couple while dialing in the feeds and speeds for this project.

You'll also probably need a miter saw and table saw and sander. It certainly won't hurt to have a jointer, planer, slab collection (yes I cut the live edges off a few slabs for this, but I have plenty more, don't worry.), and a wife who's not afraid of the Alaskan chainsaw mill. Look how freekin' cool she is cutting up that mulberry log! (had to include that pic even though I haven't used those boards for any projects yet.)

Many of the specific considerations for the font design are discussed above in the introduction. In the first tests for this project, I designed each letter individually in Fusion 360 and added the appropriate radii and width constraints in order to achieve the desired effect. After struggling through that process on multiple iterations, I decided it would be easier to simply design a whole typeface.

Luckily for me, I discovered FontSelf Maker, a plugin for Adobe Illustrator that takes some of the mystery out of typeface design. I am far from a pro typographer, but the plugin really did help in making my idea into a reality.

For about the last decade, Autodesk Fusion has been my CAD/CAM software of choice. I love being able to switch between design mode and manufacturing mode seamlessly.

Once the typeface was created I installed it on my computer and could use it natively in any program including Fusion. From there the design of projects is as straight forward as with any other method. In sketch mode, I typed words on the joining surfaces and extruded them outward by 3/4 of an inch to create the joints. The Combine tool can be used to create the mortise sides of the joint in order to skip the step of extruding a second time. There is a space in between each letter to allow for proper tool clearance. For short words, in order to make sure the joints were still structural, I added a simple round blind tenon as well as the letterform through tenons. You can see them above in the CAD image or in later steps where the pieces are shown before gluing. These details are never seen in the final objects, but certainly other decorative details could be added in your own joinery projects.

In Manufacture mode, I used Adaptive Clearing followed by a contour pass for the tenons. In early attempts I used multiple depths in order to reduce the tool load, but found over time that with a small step-over, I could cut full depth in a single pass. For whatever reason, this was not the case on the mortises, and I had to run at 1/4 inch passes. Screenshots of my cutting parameters are included in this step as well as some screen shots of the CAD. Each board was a separate body, but I did not bother with making them each a new component.

The largest project I've yet made with this joinery method is a set of shelves to hold my brother's tea mug collection. He's an expert ceramics artist and has an extensive collection of his own mugs and those made by his peers and friends. My wonderful wife wrote a poem for him that forms the joints of his mug shelves. Other projects I've made include a ring box for my wife (she said yes!) and a few other much simpler shelves.

In order to get as tight a joint as possible while still being able to get the pieces to fit, I ran tests with 5, 7 and 10 thousandths of an inch clearance. It turns out 7 was the closest I could comfortably get.

As I was working on finishing up the large shelves for my brother, I was also invited to present at the International Symposium on Academic Makerspaces, so I decided to bring some ISAM 2025 shelves and a little gift for the keynote speaker, Adam Savage. Some images above show the cutting of those pieces.

Even after clearance testing of the joints, fitting 24 all at the same time for a glue-up was significantly harder than expected. There are few things more stressful than a complex glue-up of a project with hundreds of hours of work in it already. Luckily my test joints paid off, and both large sets of shelves were successful. Tips here are to make the tendons longer than they need to be, and make clamping cauls that fit over the joint comfortably. Oh, and don't forget to put packing tape on your clamping cauls in order to not glue them in place. That takes a while to clean up, as I learned the hard way again. Thanks to Charlotte and Hayami at the MIT Hobby Shop for helping on this glue up and acting as moral support though this whole project. I no-longer work at the shop, but having access to the space and the support that comes with it has been a blessing. I believe I used every one of the pipe clamps in the shop for each of the two major glue-ups.

One of the last-minute choices I made on this project was to fill the hollow letter holes. While some letters like the 'A' don't have a hole, the 'O', 'P', 'D' and 'B' do and I had left them hollow. After filling the 'D' in Adam, I decided I liked it a lot better and filled the rest. The pieces are so small, I determined it was actually easier to do this by hand with a chisel and sand paper rather than a CNC router.

On my wife's box, and some other projects, I left the tenons longer than the thickness of the board the mortises are cut in, allowing them to stick through. While I like this effect quite a lot, some people assume when looking at the pieces, that the letters were simply glued onto an already completed box rather than being part of the joinery. I have found this is less of a common assumption when the tenons are cut and sanded flush as I did for my brother's mug shelves and the other more recent projects. To each their own, I suppose.

For me, finishing has always been one of those steps that comes with a lot of choices and a sizable amount of dread and anxiety. Too many times after a long build, I've been disappointed by the finish. In this case, I was worried that there would be a spot of glue I missed in cleanup or sanding that would act as a finish resist and show up glaringly. My colleague Dyllan suggested using spray on shellac, a product I'd not used for wood working before. I was pleasantly surprised by a test piece and decided to use it for the final shelves. Somehow it turns out, I never leave enough time for finishing, so luckily the shellac dries quickly. Perhaps some day I'll learn better time management.

On the larger set of shelves, I added a french cleat for hanging them on the wall. I like this method because they are simple to install, require less measuring, and create a strong and repeatable connection.

The smaller shelves have keyhole hardware and for these I needed to cut pockets to fit the plates. I know I could have done this on a table router, CNC router, shaper origin or nearly any other method, but I love the milling machine and it felt like the easiest way to cut these details accurately.

The poem reads:

Take a sip and tell me

What spins by slow each day

What stirs and wakes deep within

Sit here now relish in today

Here are the photos of the final project. Also included is a ring box I made for my (now) wife.

To date, I've taught two CNC joinery classes. The first was at Truro Center for the Arts at Castle Hill, a small arts center on Cape Cod, and the second was at the MIT Hobby Shop where I worked for 8 years. In each, students had the opportunity to both use my typeface and design their own unique CNC joints. Some examples are seen above.

My initial goal with typeface joinery was to make a table, and I still hope to do so. I'd love if it had 3 inch thick boards and could be cut with a 1/2 inch router bit or larger. I'd like one side to say "HOPE" and the other to say "GROW". The boards I milled for this project should be dry soon, so maybe I'll work up the courage this year.

Another future plan to take this further is more fonts. My brother-in-law who is a programming whiz has offered to help create an algorithm to simplify the typeface creation process for future iterations.

I invite you all to try out using the typeface for your own projects and would love to see the results. The font file is included on my website at this link: Please note that the license for the design allows for free use and sharing, but no commercial sales. intellectual property theft is a crime, and it's also deeply uncool.

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JOINTLY © 2025 by Coby Unger is licensed under CC BY-NC-SA 4.0