The multi-versatile keyhole bit

I really like the idea of the sliding perpetual calendars ever since I came across one on GrabCad.
I remodeled this one to make it a little more of my own and made one.

While I still liked the main idea of the calendar, I didn’t like the way the sliding parts worked. Especially having to put some sort of washer and screw on the back to hold it all together. I wanted to be able to mount these flush like a regular wall calendar.
So I started brainstorming and had the idea of using a keyhole bit to cut the channel for the slides. So with a little bit of experimenting, I found that keyhole bits are very versatile.
I found the best way to make these cuts is to clear with a 1/4(0.25)" endmill first, down to the bottom of your keyhole, then come back with the keyhole bit (I’m using a 3/8(0.375)"). For my calendars, I’m using a single pass at 5/16(0.3125)" deep. I’m using 3/8(0.375)“LG 10/24 panhead machine screws that I tap into the back of the calendar windows. The maze you see in this picture…I made two passes, one at 1/2(0.5)” and one at 5/16(0.3125)" deep. The keyhole section of my 3/8(0.375)" bit is 3/16(0.1875)" thick. This made a 3/8(0.375)" “hidden” pocket. I dropped a 5/16(0.3125)" ball bearing in and voila, a ball maze.
So with this little bit of information, I’m sure you guys can come up with some amazing, pun intended, projects for your keyhole bits.
As for the calendars, with a little more testing with fonts and toolpaths I feel pretty good about them. I actually have my first order of six I’m working on now.
Make sure you edit your G-code to retreat the keyhole bit slowly.

I changed the font for the months and double dates after I made these two.
They are much better now.


That is really cool - I like it!

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Thanks for sharing, James!


James that is a great looking set up for a callander Did you get it from Grab CAD
And what is grab cad.
Thanks Jeff Peters

Grabcad is a site which stores various CAD designs:

mostly in commercial/proprietary formats.

Can that callender file be downloaded from a format that can be used
CC pro

It was linked in the first post above:

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I got the idea from the grabcad model. The model is linked in the first post.
I just wanted to make it more my own and realized the keyhole bit could be used for the window slides.