How to Make an Ice Ball Maker




Do you want an ice ball maker like those sold online, but don't have $800+ to spend?  Then make your own!

Don't know what an ice ball maker is, or how it works?  Then check out the last page of this Instructable for a video of it in action.

You'll need access to a machine shop, and specifically a CNC machine.  TechShop provides all the equipment you need for a monthy fee.  I made it at TechShop, and you can too.

Ice ball makers work by melting a large block of ice into the proper shape.  It accomplishes this by having two large blocks of aluminum (aluminum has high heat conductivity and capacity), each with a hemisphere carved into a side, slide together to form a single continuous chamber on the inside.  What's left is a perfect sphere.

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Step 1: Materials and Equipment

The basic material is two large blocks of aluminum.  You'll need to pick a size based on the size of the ice ball you want.

You'll need blocks that are in total at least 10 times the volume of your sphere.  This is so the aluminum properly melts away the rest of the block.  My ice ball maker produces 70 mm diameter ice balls, and the aluminum blocks are each 125x125x75 mm.  That's a 13-to-1 ratio, and works pretty well.

You'll also need stainless steel rod.  These serve as the bottom vertical guide shafts.  I used 3/8" SS rod.

Last, you'll need plastic rod of a larger diameter.  This piece slides over the stainless steel rod.  I used 3/4" teflon rod, but teflon turns out to be hard to machine.  I hear that Delrin machines well.

The only extra material is whatever you think will make the final product easy to use.  I added rubber feet and a cabinet knob for lifting the top.

For equipment, you'll need a CNC mill and a lathe, and basic tooling.  The inner hemispheres will be cut with a ball end mill, and you'll want as large a diameter here as possible.  I used a 1" ball end, but smaller diameters will work as well.  You'll also need a tap and die set.

Step 2: Cutting the Blocks Down to Size

The first thing you'll want to do is to make sure you have perfectly square blocks of metal.  Extruded aluminum bar is not very square, so you'll have to do the last step.

I started with 5" square bar stock, which is 127x127 mm, and machined this down to 125x125 mm with a length of 75 mm.

You can do this on a CNC mill or just a normal one.  Get a large diameter end mill or, even better, a fly cutter, and machine down each face of the block.  For the final finishing step, you may wish to clamp together the two blocks so that even if there is a small amount of error, they still match together perfectly.  Make sure to mark a corner so that you know the right orientation!

Alternatively, you can use round bar stock instead of square, and do most of this step on a lathe.  You might like the round model better for aesthetic reasons anyway!  It's up to you.

Step 3: Machining the Hemispheres

Next, you'll want to machine out the hemispheres.  This is the hardest step and will require you to learn how to use a CNC mill and the associated software.  If you use TechShop, take their classes and play around with some easier projects first to get a feel for how the machine works.  It's not too difficult, but it requires time to learn.

The basic model is easy: use AutoCAD or the equivalent to model the original block, make a sphere of the appropriate diameter, and subtract one from the other.  This leaves a block with a hemisphere cut out.

Then, you need to use CAM software to create the toolpaths.  You'll want at least two phases: a roughing pass with a large endmill to take away most of the material, and then a finishing pass with the ball end bill to leave a smooth inner surface.  Don't try to do the roughing pass with a ball end mill!  They don't like being "plunged" directly into metal.

Finally, use the CNC machine to cut the hemispheres.  Hopefully, you've learned by practice how to use edge finders, perform air passes, and so on so that you can perform this step safely and accurately.  If not, practice some more and find someone to help you!

Step 4: Stainless Steel Alignment Rods

Next step is to make the steel alignment rods that come up from the bottom block of the ice ball maker.  As I said before, they are 3/8" diameter.

These rods need to be nearly--but not quite--the full height of the ice ball maker.  I have chosen 138 mm out of the total 150 mm.  The rods start from the very bottom of the bottom block, but do not poke all the way out of the top block.  I have left 10 mm of solid aluminum above the top block, and then gave the rods another 2 mm of "slack".

The bottom part of these rods needs to be threaded.  I used a 3/8" die, pitch 24 for the threads.  I did the threading in a lathe, but you can also do it in a mill or just freehand.  The rods need to be as straight as possible, but you can always put some slack in the system later if you need.

I also used a lathe to bevel the edges a bit so as not to leave sharp edges, and make it easier to thread.

Last, I mounted the rods in a drill press, and sanded them (ultimately using 1000 grit) for a very smooth surface.  Remember that the plastic pieces slide on these, so the smoother the better.

Step 5: Hole Drilling

Before moving onto the plastic sliders, we'll want to drill the holes that the rods slide into.

Since the plastic has a diameter of 3/4", I chose to drill the slightly smaller diameter of 23/32".  This meant that I could machine down the plastic pieces to exactly fit the way I wanted.

It's very crucial that the holes on the top and bottom pieces are exactly aligned.  After you choose your hole positions, make sure to cut both of them at the same time per block--don't remove it from the vise in-between.  Doing so will add measurement error.

Because the holes are so big, you'll want to drill them progressively.  Start with a center drill to make the starter hole.  Then, use a smaller diameter drill, and only cut a fraction of an inch at a time before lifting it to remove the chips.  Do the same with the final size drill.

The top piece has holes of depth 65 mm (leaving 10 mm above), while the bottom piece has depth 60 mm.  I left the larger 15 mm on the bottom because we'll be threading holes, and we want a bit more strength here.

Step 6: Drilling and Threading the Alignment Rod Holes

Now, we work exclusively on the bottom block.  We need to make the threaded holes that the alignment rods screw into.

Find the tap you need (3/8"-24 in my case) and the drill you need (make sure to look it up in a table!).  This should be pretty straightforward: drill the holes in the same location as you did on the top side.  As before, make sure you start with a center drill!

Then, tap the hole all the way through.  If you use lubricant, this should be very easy since it is not a blind bottom, and the chips can fall all the way through.

When done, you should be able to thread the rods into the holes as shown in the left block in the picture.

You can see in the other picture that I have added rubber feet on the corner; this protects my countertop.

Step 7: Plastic Sliders

These pieces slide into the top block, as well as over the bottom rods.  You'll mostly be using a lathe for this step.

I started with 3/4" teflon, but as I said you can use other plastics.  Approximately half the rod needs to be machined do to *just fit* in the holes you've created.  When you get close to the right diameter, only machine off about 2/1000" at a time, and check to see if they fit snugly via friction.

Next, you'll need to drill a hole all the way through of the same diameter as the metal rods--3/8" in my case.  Again, use a center drill to start with.  You may need to drill from both ends to get the length you need.

Next, you'll want to use a reamer to smoothen and enlarge the hole.  Reamers are made with very slightly larger diameters than common sizes: a 3/8" drill is 0.3750", and a common reamer size is 0.3760".  This is perfect for us since it gives us just enough gap for a smooth slide.

The other half of the rod should be machined down to a smaller diameter; one that fits freely in the hole.  Mine ended up as 0.68" diameter; you may need more or less depending on how precise you are with the other measurements.  Constantly try sliding the rod down the metal rods to make sure they enter the hole freely.

Last, you'll want to bevel the end so that it is guided down if there is any misalignment at all.  If your measurements are perfect, you may not need this, but I did.

Step 8:

You're almost done! You should be able to assemble the pieces as the picture shows.

If you want to install a lifting knob, you can do so now.  Find a nice cabinet knob at the hardware store, and figure out what diameter screw it takes (mine was 8-32).  Find the appropriate tap, and the drill that you use with that tap.  Drill in the center of the upper block (again, use a center drill!), making sure not to go so deep that you plunge into the hemisphere.  Now tap the hole, cut off the head of the screw (so that you have a short threaded rod), and tighten it up.

Step 9:

When you're all done, the ice ball maker should operate like shown above.  Perfect ice balls!

Wondering how I got such clear ice to start with?  Then check out my other Instructable, how to make crystal clear blocks of ice.

Attached are some very basic AutoCAD files of my design.  They contain the original 125x125x75 mm block and the same block with a hemisphere carved into it.  You should be able to import these into your CAM program (like SprutCAM), but I recommend starting from scratch to understand the whole process flow.
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    97 Discussions


    1 year ago

    Hey, is there any possibility to bye one of your selfmade ice mould maker??

    Thanks for answering!



    7 years ago on Step 9

    would it not work better if it was copper?
    just wondering cause it has a better heat conductivity than aluminum

    8 replies

    Reply 7 years ago on Introduction

    Copper would definitely beat aluminum in the heat conduction department, and be beautiful to boot--the main trouble is that it's so expensive! I also can't find it in the sizes I'd need; 5" square or round bar. I'm sure it exists but not at the places I've looked at so far.

    I did make a nice copper cylinder on the lathe as part of a mini element collection. It's the prettiest element of the ones I have to far, and nice and dense too--although tungsten beats it there!


    Reply 4 years ago on Introduction

    spcutler, you said: "Copper would definitely beat aluminum in the heat conduction department", but in your explanation about how the device works, you said the aluminum has high heat capacity. Indeed it does, and it has three times as much as copper. Is heat capacity or heat conductance the dominant factor?


    Reply 4 years ago on Introduction

    You need some of each. Regarding capacity, the main thing is that you have *enough* of it--it needs to be enough to melt away all the parts of your ice block that aren't the sphere. If you had a material with twice the heat capacity as aluminum, it could be half the volume.

    Too much capacity could be a minor problem. My device got noticeably frosty at the end of a run. This was an advantage because it meant the ice ball wouldn't melt any further (since it was at the same temperature). A device with much larger capacity would continue to melt the ice and the ball would become deformed unless you took it out quickly.

    Regarding conductivity, my intuition is that it should be high but not too high. Something like plastic would take way too long. However, with aluminum I found that the balls would sometimes crack if they were too cold (well below freezing) and the aluminum was warm. The crack was caused by thermal shock. Something like copper with even higher conductivity would be even more prone to thermal shock, so I think aluminum ends up being just right.


    Reply 7 years ago on Step 9

    I think you might have nailed it on the aluminum...Copper is a pain in the ass to keep clean. Tarnished Aluminum just looks a bit dull..


    Reply 7 years ago on Step 9

    true enough XD copper is so anoying to keep clean but you can plate it with zinc and it won't oxide anymore and the heat transfer won't be much affected by the microscopic coat of zinc.
    at least i think so.


    Reply 7 years ago on Step 9

    Tungsten conducts heat better than copper?
    That I did not know!
    Anyway nice instructables man!


    Reply 7 years ago on Introduction

    It doesn't, he meant it's much denser than copper. Tungsten is nearly twice as dense as lead.


    4 years ago

    Can u sell me one of these please


    7 years ago on Introduction

    New goal: get a 3D scan of my head, and then mill that into some aluminum. Perfect ice faces, every time. Thank you!

    1 reply

    6 years ago on Step 9

    I am really on a mission to make these really cool ice balls...hope you can help me out here....

    I do not have access to any machining equipment and even if I did, I am not a machinist...would you consider making one for me? I would of course pay you for the material, machine time and your time.

    Thanks again,

    Marko in Mass


    6 years ago on Step 9

    You are my hero. I've been trying to make clear ice balls for a while and your post does it all...clear ice and the ice ball machine...and a whole lot cheaper than the on-line units.

    Question : What size piece of clear ice do you need to use in the unit? Does the size of the clear block of ice matter...assuming it is big enough to fill the sphere...and does the shape of the clear block make any difference.

    I found a small mini-version of the on-line model and when I use mine, sometime I get flat spots on the ball...and I think it might be because I am using irregular shapes of clear ice...pieces just broken off a larger pc of clear ice.

    Thanks again and great instructional video.



    6 years ago on Step 9

    Way cool ! Given that you have a CNC at your disposal, I am surprised that you didn't add any runoff channels/gates, to keep the countertop dry. Since you don't want to corrupt the shape, just make an outer ring around the shape, and an outlet channel.
    I would love to make one of these for ice formed whiskey glasses, say four at a time, or perhaps shotglasses in quantity. Shape then freeze until the party. Have to make grips/indents so it doesn't become too slippery.

    Perfect for pool parties - and very little to clean up, at least for those of us who drain our glasses.

    1 reply

    Reply 6 years ago on Step 9

    That's a great idea! I was originally thinking in terms of having a small hole in the bottom that the water could flow through, but that would, as you say, corrupt the shape. And I'll admit, drilling tiny holes in a nearly-finished project always scares me! Your idea with the channels solves both problems. I was already planning on making some more, and I'll be sure to try that out if I do.

    One thing to watch out for when refreezing--because there is still a film of water on the surface, you will tend to get marks corresponding to the container you put them in. So it looks a bit imperfect, though after 30 seconds in the glass the marks will melt away.