Community challenge #12: Puzzles (closed)

Hi folks,

After exploring multi-sided machining in challenge #11, let’s move on to something different that hopefully will also get your creative juices flowing.

The theme for challenge #12 is: Puzzles

I remember making a set of four coasters designed as puzzle pieces, that would become a trivet once put together. I learned a thing or two about tolerances…but it made for a cool gift. Between simple puzzle pieces for kids and complex 3D brain teasers, hopefully there is room for everyone to participate.

The rules for this 12th challenge are:

  • submit your entry in this thread:

    • the project must made on a Shapeoko or Nomad.
    • the project must match the puzzle theme (when in doubt, PM me)
    • you must include pics of the finished piece.
    • you must include the design file (so watch out for any licensed vectors you might use, that might not be shareable)
    • tell us about your mistakes, tips and tricks, etc…
    • posting your project to CutRocket will get you a +2 bonus on the vote tally.
  • you can post multiple entries if you want.

  • timeline:

    • deadline is set to Aug 30th, midnight PST (= 3 weeks incl. 3 week-ends)
    • there will then be 7 days for voting.
      • voting will be open to legit community members only, and the jury reserves the right to remove votes from “outsiders”, and will also break any tie.

Here are the prizes for this challenge:

  • First place: HDZ 4.0 \o/


  • Second place: BitRunner (a.k.a. my preferred way to handle dust collection start/stop)


  • Jury’s prize: BitRunner


and Carbide3D swag, as it should be:


Have fun machining!


Ahahaha it is destiny saving for post later, my first “real” project on the SO3 was a puzzle, so cool to show my first real piece I did years ago, and better still, I have it on my desk and, get it up you Corona virus!!! you can’t take that away from me!!

OK so i present to you my adaptation of a puzzle box that i called "First. I gave it this loving name because it was genuinely my first for doing just about anything really, pocket, contour, cry it was all in this little bundle of joy.

Reflecting on this design i can and will improve it, but at the time i simply was not capable of making these refinements, such as pocket offset cutting, two sided cutting, these seem trivial in nature now 2+ years on.

I love looking back at this, and whilst it would be ace to win (after all this is what the contest is about), this is a little more deeper for me, this box like all our designs, are not just about fabricating a piece of material, these objects tell a story, this story / Piece is proof to all the people who have throughout my life told me again, and again that i will not achieve that much or account for anything, that i have and did!.

This is my puzzle box and a symbol to all those who face these challenges, we can and are able to do anything! we are only limited by ourselves!

Right before this turns into a deep Dr Phil / Oprah Winfrey Session lets have some fun!

So first off i will upload this to Cut Rocket, and share this design file, but please note the following warning


Seriously though, i would verify everything to make sure there are no crashes lurking. if time permits i will create version 2.0 of this with every design issue ironed out and new tool paths etc. but this is my genuine original design.

I can confirm no end mills were harmed in the making of this project.

Also please note this design will get you to what you will see in the pictures but it has flaws that i will cover.

OK now that that the health and safety police are happy for me to proceed, onto the design

The Puzzle

This is at its heart a level 2 puzzle, and is based on some very simple physics and puzzle piece placement, though it is very effective and repetitive (important for a puzzle). The puzzle does not require brute strength or force.

The Puzzle has two compartments the first has no lock or mechanism, and in my version holds a piece of paper with the rules outlining what they will get if they solve it and that if they need to force or use strength then they are doing it wrong

The second compartment holds the prize / treasure / money / insert word to describe the swag. this can only be opened after the puzzle has been defeated.





The Mechanism

The fundamentals of this puzzle is to get it to “unlock” and it does this by having a simple but effective slide lock gravity fed ball bearing mechanism.

A dowel is glued into position into the Bottom piece, then the Middle Piece is also slid down with the down going through the slot, the top piece then is also fed on in the same manner, only leaving enough Dowel sickout to allow the cap to be placed onto it, thus hiding the swivel point / axle.

The most important point here is before you glue the top cap you MUST make sure to drop in the ball bearing in

(DESIGN FLAW ALERT) when i made this, i had to draw it in Fusion360 from a technical drawing, not from an existing file, nothing wrong with that but i simply did not understand tolerances enough to realise that what i was doing was a drawing design / not a product - i hope you know what i mean, as in when i made the slot, i did so per drawing no +/- tolerance and as such was sticking allot, and as the usage increased it became stuck (more on that in a min)

Once the ball bearing is in you have the “lock” mechanism in pace.

When the puzzle if upright the ball bearing sits in the slot in the middle piece between the dowel and the slot in the piece, thus stopping you from opening the middle section because the notch prevents the piece from swivelling, because you are unable to pull the middle piece back.


I was able to do the notch on the bottom piece (mutters under breath, the second time) however i just did not have the ability or skill set to understand how to notch the Middle piece so that it would slide into it (i cheated and used a small wood chisel), but to design this flaw out i would simply cut this out first then flip part and do the rest, DUH! JON! obviously lol

This then once dry fit together should work, once happy simply glue the cap on.


There is a guy i know who put too much glue into the cap so that when i… um he, put it on to the dowel, the glue spat out and stuck the cap to the top of the puzzle. I have now told him how to fix that problem!!

The solution

Hard to hide this, and also if you are making it you are going to know - so will say spoiler alert but in honestly that is like saying you are waiting for a surprise purchase from Carbide 3D after you just bought something lol.

The first step that you need to do is to turn the puzzle box upside down - gravity will then make the ball bearing fall from Middle part into the slot on the top puzzle. When the ball falls in, it will enable the Middle part to slide backward away from the notch.

Only after sliding, the Middle part back can be turned on the dowel / axle, if done correctly the ball bearing is transferred and then exposes the opening in the Bottom Pocket.

Claim the swag and #fistpump

I tend to put money in or something that rattles as this disguises the noise the ball bearing makes when it rattles around or transitions into the slot correctly. The ball bearing is hidden within the puzzle and cannot be seen.

This will drive people mad (unless they have seen it before or know how to do it., because as they will turn it and manipulate it to try and find the was to defeat the puzzle, the box will sometimes open, however If someone accidentally opens the puzzle box, the reality is if you reset it they will be back scratch their heads!!.

So there we go, a warts and all original fail fast fail cheap puzzle that means an awful lot to me, and i hope you can use this to bring a bit of fun to your friends, family, grandchildren.


puzzle box .zip (457.0 KB)

Cut Rocket

Thanks people hope you like, and for those who are about to fight for C3D swag we salute you :slight_smile:



My second project was a “puzzle”:

I’ve gotten pretty good at solving it (the colors help a lot). But I don’t think I ought to submit it… (unless…)


In case anyone needs some ideas/inspiration/motivation suggest taking a look at a few of these:


Or see G. Maxton’s oeuvre:


Here was a birthday gift I did for a friend’s daughter. I used all MDF becuase it was going to be painted.

Project was made from 3/4 MDF.

All cuts were done with a 1/4" Compression bit .125 Depth of cut, .050" Stepover, 80IPM and 20IPM Plunge Rate.

Adding a few pictures to show how the puzzle pieces (letters) look removed.

CutRocket -

Childrens Step Stool V2 - 1x Pine.STL (315.9 KB)

Brace 1.DXF (51.4 KB) Side Leg 1.DXF (101.1 KB) Step.DXF (159.1 KB)


Incredible piece of art, and perfect inspiration for the contest. Now I want to mill one! Well a simplified version, maybe in the spirit of his micro-conundrumX3 with rounded edges that would lend itself well to milling.



Great job Scott, that’s something that the parents and later the daughter will have fond memories of!


Thanks Mike! files have been uploaded for anyone to modify and make their own!

But of course with name changes to protect the innocent…
Showing my age, yikes!

1 Like

It’s been a while since I played along during community challenges, so I’ll try something while you’re all working hard on your entries.

That puzzle cube art @WillAdams linked to sparked motivation to try a simpler one myself.
To cut corners I looked up puzzle cube ideas on Thingiverse, and found that one, with only 6 pieces:

Just importing the corresponding STLs was no fun, so I recreated the parts ni Fusion360 in a CNC friendly way, and with the intent to have flat sides when the cube is assembled, and filleted edges on the parts just where necessary to ensure machinability (I chose a 3.5mm radius on all filets, such that a 1/8" ball endmill would be able to cut them).

Here’s the assembled view,

Here’s the explosed view with parts layed out for the cut,

And here’s the victim (1.2" bamboo trivet, yes it’s a pity to cut that sweet endgrain trivet but it’s been sitting on a shelf for 6 months, I need to do something with it)

I’ll probably have to paint the parts different colors, we’ll see, I did not have thick enough stock from other woods.

Then I realized I don’t have any endmills with a 1.2" length of cut, nor any 1/8" endmill with enough reach for some of those fillets, so I ordered some and now we wait…

EDIT Aug 20th: received the endmills. I proceeded to lay out the parts as best as I could (close but leaving a large enough gap beween them for some adaptive clearing fun with a 6mm endmill)

I chose to do the roughing using a 3D adaptive toolpath, 6mm 3FL square endmill, 20k RPM, 90ipm, 0.04" optimal load, 0.6" depth of cut with spiral plunge. 0.5mm radial and axial stock to leave.

My stock was actually 30.15mm thick, I ran a surfacing pass to bring it to exactly 30mm.

The roughing pass went great. I just LOVE bamboo and how clean it comes out of the machine.

Check out that tiny shard that was left over by the toolpath, and still standing straight…what are the odds!

Anyway, that’s it for tonight, finishing pass coming up tomorrow.

EDIT Aug 23rd: well, after this little mishap, I had to redo the roughing part (luckily the stock is large enough to give me 4 tries at this). I then used two parallel finishing toolpaths, one at 0° and one at 90°. BUT since I don’t have a long enough 1/8" ballnose, I used a long 1/8" square endmill. Given the geometry, it could have worked, but is not optimal. Also, I had a number of problems with my G-code sender setup, and had to re-home between each toolpath, which did not help. It was still good to complete the cut:

Some walls are just horrible, others are fine:

And the resulting cube is… “yeah, I’ll give it another try”

I could probably spend time sanding the pieces to a better fit, but I won’t, I’d rather spend time trying better endmill/toolpaths combinations our of the machine. Now to find a 1/8" ballnose with a long enough reach…

EDIT: well this is the last day of the challenge, and I wanted to give this another go, but I don’t have a long enough ballnose yet, so I decided to do everything with the long reach 6mm square endmill, and use a ramp finishing toolpath:

which turned out to give a near perfect finish (considering the sub-optimal use of a square endmill for finishing…) right off the machine,

And a better fit:

I would still need to work on my tolerances, I have enough stock left for ONE final try.


Very nice take on a block puzzle. I have done this style, and a number of burr puzzles, with students over the years. Unfortunately, all of those are in storage at the school, and I can’t get to any of it. Might throw a design file or two up, as I have those.

Anyone looking for ideas, look up `notchable burr’. Fairly straightforward. Lots of fun.

I will be submitting a new project here when I get the time to do it (engineering life hit me hard this week), but something a little different. The CAD is done, but the CAM is rather special.

EDIT: added models for BURR 305, one of the most difficult to solve notchable burrs. The models for the parts are in Inventor, so I present STLs here in the interest of simplicity
Part2.stl (2.2 KB) Part3.stl (1.4 KB) Part4.stl (3.0 KB) Part5.stl (3.0 KB) Part6.stl (2.0 KB) Part1.stl (2.2 KB)


Here are some coasters I just made specifically for this challenge. Theyre each comprised of “seven segment” style numbers 0 through 9. The numbers were machined out of starboard and the base was made out of pine and some other scrap wood I had on hand. I got the idea from a tik tok video of a similar puzzle that was 3d printed, and deisgned it in fusion 360.

Fusion 360 Link:
CutRocket Link:

The design work was much easier than I expected, I ended up just making a sketch with a grid and connecting the dots to get the basic shape of the numbers. I then used the size of the numbers to create a box to hold them. After adding some fillets it was all done.

I also made a render to easily differentiate the numbers and solve the puzzle.

All of the CAM was sone with fusion 360. This was my first time working with the new manufacturing model feature and the arrange feature. Both features were really helpful and allowed me to do CAM on the numbers without “dissassembling” the model or needing to make copies. The toolpaths were just 2d contours with an 1/8in Amana plastic cutting endmill and then a 1/16in endmill to give the corners a tighter radius. The first set was cut with tabs but I had an issue with the tab sizing and spacing so for the next set I just used the painters tape and glue trick.

For the box I used an adaptive toolpath to rough out the middle with a 1/4in endmill and then came back with a 1/8in mill to clean up the edges. I used a 1/4in ball endmill with a steep and shallow path to add the fillet to the edge of the box. I’m really glad I added the fillet to the second box, I think it really makes the box stand out and look more professional.

The first round of machining didnt goes as well as I had planned, I accidentally set the tabs to be way too small and they ripped and caused the numbers to shift and get roughed up. I ended up repeating the process but instead of tabs I used painters tape and glue to hold down my stock. This worked flawlessly and the numbers came out really crisp. After manufacturing the base I realized my tolerances were off and the numbers could barely fit, so I ended up remaking it with a slightly larger opening and with the added fillet it turned out amazing.

While using the manufacturing model I accidentally chose the wrong sized stock and my router ended up cutting through my toe clamp on the first run. Thankfully all I had to do was 3d print another one.

After making sure everything fit correctly I stained the wooden boxes to be slightly darker in order to better contrast with the white numbers. And after that I had my final products. Hopefully theyll make some nice coasters for my new appartnment and at least be a fun conversation piece.


Awesome! (and welcome to the community)
This goes to my “I need to do one of those myself” list. How large are they ? I would probably like to make a single trivet-sized piece.

I have not yet had a chance to look at the new manufacturing model features in F360, sounds interesting.

p.s.: don’t forget to include the link to your f360 project, and post it to CutRocket for bonus points.
p.s.: very cool combat robots too !


Thanks! The two I made are 5.3x6.3 inches but they can be scaled up or down relatively easily by editing the original sketch. The new manufacturing model and arrange tools feel like a nice improvement, Product Design Online released a good tutorial that explains them really well.

Thanks for noticing the robots by the way, Ill probably make a few posts about them on here soon!

I also added the fusion and cut rocket links to the top of the post!


Gopher hole puzzle

Walnut pieces with a sapele box, both finished with Danish oil

This is a classic puzzle and the pieces could be made in a number of ways, but having the precision-aligned CNC holes is visually appealing, and pocketing them out felt safer than using my drill press. A machine fit for the “buttons” could be designed but I did not take that route.

“Top”: Gopher Hole No Thru.c2d (254.4 KB)
“Bottom”: Gopher Hole Thru Cut.c2d (243.3 KB)

The puzzle design

The main square is 2.55" × 2.55" × 1.4". I used a thickness and width of wood I had available, hence the strange dimensions. I am new to CNCs so I put the design together in Illustrator and exported SVGs into Carbide Create. I used a 0.25" end mill and a 60° Vee bit to bevel the buttons and holes. I also modeled the pieces in Solidworks for extra practice and renders. One could easily add more pieces but I feel 6+2 is an appropriate level of complexity. There is also one duplicate piece.

The puzzle has taken both of my test subjects about 25 minutes to solve. There is one satisfying and simplifying "Eureka" moment:

As an example, a piece with 3 buttons on one side and 0 buttons on another side should obviously be placed with the buttons into the holes at the top or bottom of the puzzle. There are two such pieces in this puzzle (#2 and #3) (and one more “lucky guess” piece: #5). With this clue, it may only take 10 minutes to solve the rest.

Making the puzzle & lessons learned

  • Care must be taken to mirror the pieces correctly for the top and the bottom.
    It was hard for me to visualize the pieces and match the buttons and holes properly. I accidentally cut one set of holes right on top of a set of buttons…

  • To orient the piece when flipping:
    For the top of the pieces, I referenced off the bottom-left of the SVG. For the bottom of the pieces, I flipped the board across y and referenced off the top-left of the SVG. This was enough precision for me!

  • The pieces are probably best cut out on the CNC.
    I planned to draw the outlining rectangles using a CNC pocket and then use a table saw to cut them out. I would recommend using the CNC and tabs to dimension everything! This should improve safety and reduce sanding time.

  • Plan your containing box ahead of time!
    Consider oversizing the bottom and top hole grids so they fit in rabbets. My box has simple butt joints with homemade walnut dowels. I haven’t included any “plans” for the box as part of this project.

(Forgot to take a picture when she solved it!)


I love this, intact I love just about everything about it, well done. And I feel you are going to be someone to keep an eye out for, welcome to the Community!!



How are your projects coming along guys ?
I did the roughing pass for my puzzle cube tonight (I edited my post above to include a few pics), that was interesting (#BambooRocks)


Perhaps fortuitous that you didn’t have thick enough wood in another species, the bamboo looks great!
Looks like the runtime was going to be about 21 minutes, what did thee actual runtime turn out to be? Which end mills did you end up acquiring for the depth of cut required?


First attempt in aluminum going! Using classic belt Z and first part came out pretty nice and clean, with some small burrs to sand off:

Edit: Testing multiple variants of toolpaths in the same piece…learned quite a bit:

A much better result from lessons learned (and the pieces fit)! :

The Z-belt is having no problem chugging through the Aluminum which has been pleasant to see. The one annoyance has been with how thin of an onion skin to leave without accidentally punching through and having the workpiece start to get pulled up (!). I’ve found about 0.002" to be working for the moment.

I’ll update this with pics and more as I get through it. I’m holding my breath and seeing what tolerances I can get for this to work. 40 more pieces to go!