Making Your Own Custom Coin

Welcome back to Switch & Lever! Today we’re going to make a coin using a CNC
mill. If you’re only interested in cool milling shots I suggest to skip forward to the time
indicated on the screen. Otherwise, let’s get started! Coins have been around for virtually forever, from small to large, from round to square to whateverthehell
shape this is. In metal, wood, plastic and maybe most importantly chocolate!
Gods, kings, queens, fictional characters and celebrities all have
their own coins. There are even coins which aren’t actual coins nowadays! So, why
don’t you have your own? Let’s change that, shall we? While there are many concievable ways to make
a coin, in this video we’re going to look at making a coin in 3d, together with a realistic
head, and milling the result on a CNC mill from a piece of brass stock. Now, there are two ways of making a realistic
looking three dimensional head on a coin, without modeling it from scratch, but unfortunately
both are somewhat time intensive. First one is perhaps the easiest one, but
it does require you to aquire an actual 3d model of your head. There is software, even
free software, from Autodesk called 123D Catch, which can take a series of photos and stitch
together a decent 3d model. For an entire head you need to sit perfectly still while
someone photographs your head from every concievable angle. For an entire head you could need between
50 and 100 photos to get a decent 3d model from it. However, if you’re only doing the
profile you could get away with less, as you could limit yourself to only doing one side
of your head. There are plenty of good videos and tutorials on how to use 123D Catch to
scan things, I suggest you check them out. Anyhow, once you have the 3d model basically
all you need to do is bisect it down the middle and squish it down so it’s thin enough to
fit on a coin. Model the rest of the coin features around it and this will be the geometry
which will guide the CNC mill. The second method is good if you don’t have
access to a 3d model to begin with, or means of making one, but you do have access to a
photo of the person you want to put on your coin. To use it on the coin you’re going to
convert the photo into what is called a depth map, in which parts of the photo which are
closest to the camera are colored white, and things furthest away colored black with everything
in between being a gradient of gray. Unfortunately, there is no easy way to simply convert a photo
to this, so it would require some hand painting in a photo editing software to get the image
to how it should look. In your 3d software you need to find a function
to displace geometry using the depth map you just made. This is done differently in different
programs, but look for displace or in some cases it may also be called heighfield. You
may need to go back and forth between the photo editing and your 3d software a few times
to get the desired result, each time fine tuning the photo a bit. Once done model the
rest of the coin around it and you’re ready to go onto the next stage. But first a slight detour, while this video
is about milling a coin, there is nothing stopping you from taking your 3d model and
using a service such as Shapeways to 3d print your coin, even in metal. Be aware though
that the cost difference between doing it yourself and having it 3d printed is prohibitive.
So, if you have access to a CNC mill then that’s the way to go. For this video we’re
going to be using a Roland MDX-40A mill, which is really not made for milling metal, and
requires some special attention to do so. Because this mill is used mainly for milling
softer materials using double sided sticky tape on a MDF base is usually sufficient for
work holding, even for high speed machining. Don’t, like me, be fooled into thinking that’s
enough to hold when milling metal however. Even if the tape holds the piece isn’t secured
properly, it will vibrate and the result will be undesireable. Because of this an entirely
new bed was made for the mill out of a sheet of aluminium plate, into this four holes were
drilled and tapped to securely hold down the workpiece. Since we’re going to be milling both sides
of the coin we need to make sure we can reliably mill the backside aligned with the front.
Therefore the workpiece was drilled with four holes matching the holes in the new bed for
the mill and the centerpoint of them was marked so the mill could be zeroed on that point. As this machine is not meant for milling metal,
even a soft metal like brass is tough on it, so the milling had to be slow, taking only
fractions of a millimeter at a time. Here we’re using an engraving cutter with a 90
degree included angle as it provided both sturdyness and could create some finer detail
than a ball ended endmill could do. As this wasn’t a production run and I wasn’t going
to make a lot of coins the speed wasn’t much of a bother. It took between 2-3 hours per
side of the coin, starting with a roughing pass to get most material out and then a finishing
pass for the last fraction of material to be milled away. Once the first side is done we’re going to
flip the coin to make the backside. If you marked the centerpoint and centered the mill
well for the front the backside should be milled in the right position without having
to reset the zero point. While doing it by eye isn’t the most exact method with care
you can still get it within a fraction of a millimeter, close enough for no one to notice
if the alignment is off or not. Make sure you’ve designated the screw heads as no-go
zones for the mill as well, so you don’t accidentally crash into them. I chose not to mill out the circumference
of the coin, mainly because the milling machine was underpowered. I did though mill up to
a ledge which could serve as a guide when taking the coin to a belt sander to hog away
most of the remaining material. The plastic was put there to protect the bottom of the
coin from scratching. Setting up an angle plate and another piece
of plastic and wedging a file inbetween allowed me to hand file a right angle shoulder all
around the coin in a much more controlled fashion than the belt sander would allow.
While time consuming it gave a very nice result. When you’re done you’ll have a very nice looking
coin, but in my opinion still a bit boring. It’s just bare metal, and it doesn’t have
life to it. Fortunately, that’s easy to change, without having to handle it for a long time
to build up natural patina. Since we made this from brass there are many different ways
to create patination, such as using liver of sulphur. Unfortunately, not having access
to that meant finding another more direct method of creating a similar look. Enter the
blowtorch! Heating up brass removes the shine, oxidizes the surface and makes it dull and
unattractive. No worries, we’re going to fix that with some matte black spray paint! Just
give the coin a quick coat and then quickly wipe off as much paint as you can before it
dries. This leaves paint in the recesses and makes it look dirty, but still doesn’t quite
bring the coin to the look we want. That’s what we’re fixing in the next step however.
Once the paint is entirely dry we can use a metal polishing compound, like this Autosol,
to polish up the high spots of the coin. The reason we burnt it in the beginning is because
we want to create a layered patina on the final coin. Some areas will be dark because
of the paint, some will be lighter but a bit dull because of the burnt oxidation and the
high spots will be nice and polished. Dirt and grime doesn’t happen uniformely in the
real world, so try to emulate that for a more realistic result. When you’re done it’s possible
that the paint looks a bit grayish because of the polishing process. To make it darker
you can treat the coin with a bit of linseed oil. It will absorb into the paint, darkening
it and then harden over time. Time to knock this up a level! A custom coin
is all well and nice, but if you do have access to a CNC mill making a nice box for it is
a fairly trivial matter. I ended up taking a piece of oak, cut it in two and milled out
a book matched box with recesses for three coins. While milling out the circumference
of the actual box notches were milled for hinges and small recesses in the corners to
hold neodymium magnets to keep the box closed. The coin recesses also were made slightly
deeper in the front allowing the coins to be easily removed by pushing the front of
the coin down so the back pops up. If you have a camera in a dusty or grimy environment
and you still want to get up close and personal with what you’re working on covering the camera
with saran wrap will work great. Just make sure you stretch the plastic across the lens
so there are no folds or bumps distorting the footage. Once the box is done and assembled give it
a quick oiling or varnishing and you’re done! Look at that fine ass box! Thanks for watching this episode from Switch
& Lever! While you’re waiting for more material be sure to check out one of the older videos,
and please do subscribe if you haven’t already! Until next time!

100 thoughts on “Making Your Own Custom Coin”

  1. Wow that turn out great the my first project in my cnc was a coin and it turn out really bad also i broke 2 carbidre end mills

  2. Damn, I really feel like doing this, but the machinery… wondering if it's possible to just take the brass (or an existing coin) and make what you want with a drill bit and tons of patience.

  3. It is probably not cheap to make your coin, sure metal is cheap enough if wanting a silver coin, but to get a place to do this for you would be very expensive.

  4. Heres the actual questions though, The machinery needed to make that is quite complicated so it would be beneficial if maybe the equipment was also in the description. Im guessing its thousands of dollars at least, so if one needs to find somebody to do the imprinting of the coin once all the graphics and 3d modeling was finished, they know what to ask for.

  5. To make the coin even more realistic, just put them in a bucket of gravel and shake it to add texture to the metal (like a tumbler).

    Just a small advice : add more caracter to that dull robot voice you have …

    Btw such a great idea that small recess at the bottom of each coin pocket to easily take them out.

  6. Question sir: "if your cnc machine is not intended for metal, how about milling plastic and use it to make a mold for metal?"

  7. Sure! Make your own coin. If you have 3D software and the experience to use it, a CNC machine, tooling, CAM software to create the program from the 3D software, and the knowledge of how to import the program, touch off the tools, and run the machine. No problem!

  8. My first thought when seeing the box: What? No brass hinges? 😉

    Very cool project – thanks for sharing it 🙂

  9. If you have something in the way of a rock tumbler you could add wear and smooth out some of the layer lines with some very fine sand.

  10. Hello, it's a great video and very detailed.

    What kind of blade do you use for bronze, I would like to try it with my cnc.

    You think that the cnc has to have a great power to do this.

  11. For everyone that want to make their own coin but don’t have that machine take a coin sandpaper it and then go saltwater metal etching (search for meatballs etching tutorials)

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