Mastermind Game With Rack & Pinion Box Latching Mechanism

Well, I didn’t get to proof this quite as well as I wanted to, because my 'Forge has decided to go wonky on me. But I did manage to get enough of the prototype done to verify its functionality, at least, and I know a few people are waiting for it and I don’t want to make them wait any longer. So here it is:


NOTE: The little part with the living hinge needs to be rotated to match the grain of the wood before cutting. I couldn’t fit it on my project page in the correct orientation for cutting on :proofgrade:, and forgot to mention it when I posted. :roll_eyes: (thanks for the reminder, @marmak3261!

Engraves and scores are in blue. My “final” build in the photos below is missing some of those, because my 'Forge is having issues with them at the moment. :frowning:

For the model in the photos, I cut the game board (center top) from PG medium red oak hardwood, and the inner box bottom (lower right corner) from PG medium clear acrylic; everything else was cut from PG medium maple plywood.

My plan is to cut the playing pieces (2 sizes of pegs to fit the 2 sizes of holes in the game board) from PG thick acrylic in various colors, but I want to play with rounding the tops, which requires engraving capability, so for the photos I’m just using temporary ones I threw together from scraps last weekend (I hadn’t received my acrylic order yet) so my granddaughter could help me play test it. :slight_smile:

Note–assembly photos include a couple of different models, since I’ve been experimenting, and didn’t always remember to take photos of every detail; I hope that’s not too confusing! Also, my craft table is messy and I’m too lazy to clean it up just for assembly photos. Don’t judge me, I’m giving you free stuff. :stuck_out_tongue_winking_eye:


Before cutting, you might want to put sticky stuff on the back of the game board, to stick it to the box top with. Or you can use glue. I used double-sided duck tape, and even remembered to change my material height to compensate!

The piece with the two little lock icons is the inner box bottom. You can dab some paint in them before peeling the masking, if you want to make them show up better. If you cut it from acrylic, you’ll need a spot of white paint on the back, too, or they really won’t show very well.

Start with the gear assembly, which mounts on the inner box bottom. Lay it on your desk with the lock icons facing up, and use the 5 toothed pegs (and dabs of glue appropriate to the materials you’re using) to attach the gear spindle and the two triangle-ish pieces, like this (this was a pre-lock-icon model):


Now assemble the box sides and inner partitions (gear side goes down):


Turn it over and finish the gear assembly (switching to the acrylic-bottomed model now – ignore the missing partition; I hadn’t convinced my ailing 'Forge to properly cut it yet):

Place the gear so that the lock icons show through the holes (they’re there, honest – I hadn’t added the white paint yet, so they’re hard to see):

Then drop in the pinions and position them so they stick out through the end slots – this is what will lock the box together. The two corner pieces are there to cut down on wobble, and are glued in place, flush against the sides of the box.

If you want to add wax to the slidy parts, now’s the time to do it. I didn’t find it really necessary – everything slides pretty nicely straight out of the 'Forge.

Now you can add the bottom of the box:

Here’s how it looks from the inside (if you’ve used the acrylic):

Next, the box top. Assemble the sides, then put on the top. The one in the SVG has letters engraved on it that will show through the holes, but my 'Forge refused to let me have them. (The 3 tiny holes are to eliminate vacuum when you’re opening the box.):

Sides (draftboard):

With top (maple):

Now you can stick on the game board using whatever method you’ve selected. It’s sized to fit between the finger joints, because @timjedwards thought it was prettier that way, and I trust my baby brother’s artistic taste. :wink: The single small hole will end up in the slot at the top end of the board, and the two in the opposite corners will show through the lower-most small peg holes.

Now put them together and try out the locking mechanism! (There was a henna artist at our office party the other day, so I’m rocking the New Age look right now.) :wink:

The last bit is the little shield that keeps the “guesser” from seeing the solution he/she is trying to figure out. Give the little living hinge a few gentle bends to loosen it up before you try to assemble it. Dripping water or alcohol into the slots while you gradually bend it farther will help make it more malleable so it doesn’t crack.

You’re kind of on your own for the pegs, for now at least. You can copy the holes from the game board for sizing. I’m thinking probably 30-40 each of 5 different colors for the large pegs, and 40 each of black and white for the small “scoring” pegs. For scorekeeping you just need one each of two different colors, or you can just use black and white.

And here’s how it looks all together:

Parts storage:

There you go. Now show me what you do with it! :slight_smile:


Awesome! (And past my bedtime.) :smile:


This is just amazing! I’m loving the clever closure and the decorative finger joints. Thanks for your generous share.

Off-topic, but how do you like the double sided duck tape? Been considering getting some.


I love your work. It so well thought out! Thank you for sharing your logic. :slight_smile:


Used to love this game! Haven’t played it in years! Very nice design! Kudos! Love the living hinge, the gear, and the finger joints!!

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You are more than generous for giving the community your files of your great work.


Wow. This is just amazing.


It looks beautiful! Thanks so much for sharing!


Very nicely executed, great share!


Wow. So Very. Now I just have to wait for it to get cool again here.


Off-topic? I didn’t think that was a concept in this forum! :wink:

I used it for attaching my lasercut (draftboard) shelf labels that I posted here a while back, and those have held up great. This is the first time I’ve attached a larger surface area like this with it. The hardwood had a bit of warp in it, so I left it clamped overnight to give the tape a chance to “set,” if that’s a thing. I’ll report back on how well it holds up.


These complicated designs are so difficult to pull off and demonstrate some serious skills and determination. So much going on here and a great use of the work space.


Absolutely beautiful! So many nice ideas converging into a cohesive whole.

I wonder if it would be too inconvenient to make the pegs the same height as the holes? No mistakes allowed…

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You helped! :slight_smile:

Re: Shorter pegs, that would have saved me a lot of time and effort spent gluing together 1/8” scraps to make 1/4” pegs! The scoring pegs would be difficult to manage at that size, though, wouldn’t they?


One could play with the cutting scraps to see…

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Takes it away from being 100% laser, but how about using laser cut dowels? By that I mean sizing the holes to the diameter of purchased dowels, then affixing the dowel horizontally to the tray with masking material and cut a series of vertical lines spaced to the height that you want the pegs.

All the pegs would be exactly the same size, much finer precision than I could get on any saw. It’s laser cheating a little, but not too badly. It would save a lot of glue time.

For that matter, why do scoring pegs have to be round? You could cut a long rectangle that is the same width as the height of the flat stock material. Then slice down that rectangle to get square pegs of the height you wanted. Of course, you’d have to adjust the holes on the board. You can’t fit a square peg into a round hole. :wink:


Yes you can, you just can’t fill the hole. There’s always a square cross-section available in every circle. :wink:

But I really like your rectangle/square “dowel” idea. Too often we think in terms of what we traditionally use like round dowels. No reason not to cut out our own square ones to align things or hold them together.


LOL. It’s so easy to tell the engineers on here some days.

We just can’t help ourselves :smiley:


I did know that even though I’m not an engineer, and I don’t even play one on TV. :nerd_face:. I just always liked that inaccurate saying!


One of my favorites:

Optimist: “The Glass is half full.”
Pessimist: “The Glass is half empty.”
Engineer: “The Glass is twice as big as it needs to be.”