In this post you’ll learn how to build a wood DIY perpetual flip calendar.
In this post we take a look at how to build a wood DIY perpetual flip calendar courtesy of Reddit user measuredworkshop. If you’re into woodworking and DIY projects or enjoyed this post be sure to check out @measuredworkshop on Instagram. He also has an awesome YouTube channel with close to 100 thousand subscribers.
This wood DIY perpetual flip calendar is a great beginner to intermediate woodworking project.
Finished project glamour shot first. These perpetual flip calendars were (maybe still are?) pretty popular as souvenirs at tourist spots. My parents have a small metal one that’s from Washington DC that seems like it was made sometime in the 1950’s.
Every time I go visit, I set the correct date on it out of habit, but I could never for the life of me figure out how it worked. I knew it had tiles inside and they somehow shuffled through, but in such a compact space, it just didn’t add up!
At the very least, I wanted to see how the numbers were arranged in there, but I didn’t want to destroy the thing. Google patents to the rescue:
Patent Link – William C Hiering
Patent Link – Howard L Fischer
It really is as simple as it looks. The tiles just stack and fall to iterate through the inside of the calendar. I guess the “magic” bit is that the center divider needs to leave room for just one single tile to slide through.
I decided to make my own DIY perpetual flip calendar just as a proof of concept, and because I knew wooden tiles would sound satisfying as they clinked through when you flipped it.
Not difficult math involved here, but I had a hell of a time figuring out how many tiles I’d need. I wanted the calendar to show the tiles shuffling through so I wanted to make the tiles different colors (I thought having different colors would make it easier to watch a specific tile iterate through).
How many colors would I need to go evenly into the number of tiles? I decided to go with 3 colors over 15 tiles, but that meant I had to cop out and make a 30/31 tile. I felt like it was a better decision than overshooting the 31 target and having to take up the slack with a “Thanks for playing!” or “Turn calendar one more time to reset to 1” tile.
I used walnut heartwood (dark), cherry (medium), and walnut sapwood (light) as my woods of choice for the tiles. Walnut was not the best choice, in retrospect, it came out way too dark, but I can always go back and use a white paint pen to make the numbers pop.
I ripped 1″ strips of each type of wood on the tablesaw, then resawed them down to about a 1/4″. This was still not thin enough. For 15 tiles, that would make the calendar at least 4″ thick and that would look stupid. So over at the thickness planer, I took the 1″ strips down to under 3/16″, almost 1/8″.
I added some decorative fluting on each side of the strips by making a shallow kerf cut on the table saw. I’m not sure they were totally worth it, you can barely see them in the final product, but enough so that it looks nice when you notice them.
I set up a stop on the crosscut sled and hacked the 1″ strips into 2″ tall tiles. Five tiles of each of the three types of wood.
I’m not amazing at lettering, don’t let the gif fool you. Off camera, I did a lot of sanding it back off and then eventually got smart and switched to pencil so I could refine the numbers as needed. The numbers are not even close to being uniform in style or size, but they look good enough to tell you the date.
I started with the odd-number side of each tile. Then each tile go flipped end-for-end and the corresponding even number was drawn onto the reverse side. This will change depending on how many tiles you choose to have, but for 15 tiles, the correspondences are:
1/16, 3/18, 5/20, 7/22, 9/24, 11/26, 13/28, 15/30&31, 17/2, 19/4, 21/6, 23/8, 25/10, 27/12, 29/14
After taking a few nights to do a few tiles at a time so I wouldn’t get sloppy, I sealed the tiles with a few coats of spray lacquer.
With the tiles done, it was time to make the enclosure of the DIY perpetual flip calandar. It didn’t need to be anything fancy, but it needed to house the tiles in a pretty snug environment; a lot of extra space might let the tiles jiggle around too much and potentially get stuck.
I decided to do miter type joints rather than box/finger joints just as something different. I took some scrap thin walnut stock and started with what would become the front and back faces. I hacked them down to 5.75″ x 1.75″ on the tablesaw.
To make the miters, I used my morso guillotine. Man, I love that thing, it was such a cool thing to find on Craigslist and it comes in handy more often than I would’ve guessed (keep an eye out for one if you can!). It’s a pedal operated guillotine that makes really smooth, clean and accurate 45° miters.
For the tops & bottoms, I decided to go with a slightly more complex miter so that I’d have more surface area for the glue to grab onto (since I didn’t plan on doing splines or anything to reinforce the joints).
This meant making a shallow cut into the top & bottom pieces (2″deep x ~1.75″wide X 0.25″ thick blocks of walnut). Those cuts were made about 3/16 from each end. I then took them back to the guillotine and hogged out the remainder at a 45° bevel so it would mate with the front & backs.
The front & backs needed viewing window so you could see the tiles. Rectangular tiles would be best viewed through a rectangular window, but I didn’t feel like getting out the scrollsaw. So I made an artistic decision to use a large (7/8″) forstner bit to hog out a circular viewing window. I drilled the hole 1.25″ on center from the bottom of the front & back panels.
I cut out only one side out of scrap walnut since I’d be making the other side out of acrylic sheet. I chose the nicest looking 1/8″ scrap and cut it to dimension.
The last bit needed was the center divider. I also wanted it to double up as a pivot so it needed to be thick enough to accommodate a through bolt. It also needed to be wide enough to only allow one tile to slip past it. The final dimensions ended up being 1.375″ x 0.5″ x 1.625″. I drilled out a 1/4″ hole to accept a through bolt and all the parts were ready for glue up!
I only glued the pieces in place rather than use hardware. It should be fine, this thing won’t see much abuse or strain. After the glue dried, I drilled through the pivot block to transfer the hole for the bolt to the side of the box.
A light sanding and a couple coats of poly and the box was done! I just needed the other side, which was just a piece of acrylic cut to dimension using an Xacto to score it and some downward pressure to fracture it. I drilled the corresponding 1/4″ hole in the acrylic window and the box was ready for assembly!
There are choices to be made here. You can “program” the calendar to count up when you tilt towards you or away from you (and backwards when you tilt away/toward, respectively).
I chose to flip the calendar away from me to iterate the date, so in that case, the bottom gets tiles 1,3,5,7,9,11,13,15 and the top cavity gets 29,27,25,23,21,19,17 (in that order if you’re looking at the calendar)
I used a brass threaded rod and two brass connecting caps to create the pivot ends and to hold the acrylic window in place using just pressure. Again, this thing won’t see much abuse, that’s plenty force to keep the acrylic window secured.
The money shot.
It might be a little difficult to see how the tiles iterate through the calendar in a gif, but it’s very satisfying, both visually and because of the sound it makes as the tiles clack against everything.
It works pretty well, you can spin it pretty fast and still have the tiles fall as they should to iterate. I didn’t show it here, but you are able to spin it the other way to count backwards.
That could be useful if you use it to make something other than a calendar using this mechanism (a counter for MTG or something?).
I was just going to leave it there, I actually like flipping it by hand, but to properly finish the DIY perpetual flip calendar, it needed a stand. I used a block of oak that was fire wood that I had squared up on the jointer.
It needed a slot big enough to fit the final calendar, so I measured out a 2″ wide chunk and hogged it out on the bandsaw. A belt grinder was used to clean the inside of all the cut marks left by the bandsaw, and I lobbed off some extra height so that the calendar would sit as low as possible in the stand.
Two holes were drilled 0.5″ down from the tops of the ears to accept the pivot parts. More sanding and polyurethane and the stand was done. Time for assembly!
Final assembly is as described above except with the stand in line now too.
Yep, it counts all the way through, perpetually. “What about February?”… I know. You could potentially make a really thick one of these with 365/2 tiles so that every month has its perfect amount of tiles, but then “what about leap years?” is a valid question.
At this point, February is a short month and you get bonus flips, easy enough. This is just a proof of concept after all, there really ought to be a way to keep track of what month it is too.
In fact, the manufactured souvenir ones do. If you’re lucky enough to have a 3D printer, you can even print a DIY perpetual flip calendar that is pretty slick looking AND has a month tracker.
DIY Perpetual Flip Calendar Conclusion
If you liked this post then be sure to check out more from @measuredworkshop on Instagram and on YouTube. If you still haven’t met your daily dose of DIY then check out our other DIY build logs. Lastly, remember that with enough research, planning, and determination you can accomplish any DIY project imaginable.