Introduction: 8-Ball in Solid Wood Cube

Picture of 8-Ball in Solid Wood Cube

There is something magical about wood puzzles. This mystery leaves the mind searching for any rationalization, any form of understanding that will answer the question of "How did that happen?" In this instructable, I will show you how to put an 8-ball into a block of wood so you can leave others searching for an answer themselves.

Step 1: Parts

Picture of Parts

You will need:

Step 2: Joint and Plane 4x4

Picture of Joint and Plane 4x4

Using a joiner and planer, take the overall size of the 4x4 down to 3" x 3" and cut into a 3" x 3" x 3" cube.

Step 3: Mark the Center of the Cube

Picture of Mark the Center of the Cube

Using a straight edge, mark the center of the cube so you know where to drill the holes.

Step 4: Router Edges

Picture of Router Edges

Using a 1/4" roundover bit, router the cube starting with the end grain using a push block to prevent tear out.

Step 5: Drill Holes

Picture of Drill Holes

Using a 1-7/8" hole saw or forstner bit, drill out the center. Drill one side of the end grain then the other. Slowly work your way around the cube removing the wood plugs as you go.

Step 6: Sand Cube

Picture of Sand Cube

Using sandpaper, smooth the cube and remove all sharp edges from the drilled holes. This will help later when the 8-ball is placed inside the cube.

Step 7: Soak and Boil the Cube

Picture of Soak and Boil the Cube

Using enough water to cover the cube, soak it for at least 24 hours. I soaked this cube for 36 hours just to be safe. After soaking, boil it for an hour to ensure proper saturation. Since wood floats, place something on top of the cube to hold it underwater. I used a glass vase I had nearby.

Step 8: Lubricate the 8-Ball

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I covered the 8-ball with paste wax to act as lubricant for the next step.

Step 9: Press 8-Ball in Place

Picture of Press 8-Ball in Place

After the cube is finished boiling, use a bench vise to press the 8-ball inside the cube through the end grain. Do this slowly to prevent the wood from cracking. If you push cross grain you will split your cube. I used a cut off piece of PVC to press against the 8-ball to protect it from the vice.


The reason this step works, is because of how trees are formed. Pretend that the bundle of matches in the photos above are the straw-like fibers of a tree (xylem). When the fibers of the wood get heated and saturated with water, they become flexible and stretchy. This allows you press the ball through the end grain of the wood. If you try to press the ball through the side grain, the wood doesn't move as easily, and in our project you risk possibly breaking the cube.

Step 10: Final Sanding

Picture of Final Sanding

The cube will no longer be smooth because it soaked in water for so long. Once the cube dries overnight, sand it smooth. Be sure to sand the inside of the cube as well. I found the best method was to do it by hand to prevent scratching the 8-ball.

Step 11: Apply Finish

Picture of Apply Finish

I finished my cube with a beeswax oil mixture found online. Apply liberally with a rag. I used this finish for two reasons. If there was still water inside the wood I didn't want to trap it there and risk the finish bubbling, and I didn't want any finish to change the look and smoothness of the 8-ball.

Step 12: How to Remove the 8-Ball

Picture of How to Remove the 8-Ball

Other than potentially boiling the cube and 8-ball again and repeating the process done before, the only way to get the ball out is to break the cube around it. Using a chisel, this test cube was no match and the 8-ball was easily removed.


Scumbdyoit (author)2016-02-06

The three holes drilled through the cube in perfect alignment intersect at eight points that outline an inner cube. The largest sphere that could theoretically fit in the puzzle would contain that inner cube, i.e., the length of the diagonal between opposite corners of the inner cube would equal the diameter of the inner sphere.

The diameter of the drilled holes would equal the diagonal of a face of the inner cube. If that hole diameter = square root of 2, then the edge of the inner cube = 1, and the cube diagonal = sqrt 3. Ratio of max diameter of inner sphere to drilled hole diameter is sqrt 3/sqrt 2 = 1.732/1.414 = 1.225:1. That could be increased slightly by sanding the corners of the inner cube.

Diameter of a solid sphere to be forced into the puzzle is limited practically by the compressibility and resilience of the soaked & boiled wood fibers. Ratio of the standard 8 ball diameter (2.25") to hole size (1.875") is 1.2:1, close to the maximum. I'm surprised it works so well. When all is said and done, what is the resulting diameter of the hole you forced the ball into? In other words, how much were the wood fibers permanently compressed?

Ricardo Furioso (author)2016-01-31






I love it.

Please do more.

ditto! x^D

avayan (author)2016-01-31

I can tell you that from all the ideas that came to my mind on how to do this, your solution didn't even surface. And I must admit I don't think any of the solutions I thought of would have worked. Quite enlightening, so thanks for taking the time to illustrate!

tpobrienjr (author)2016-01-31

I like it! The science lesson is good, too!

dianadfonseca (author)2016-01-31

Looks pretty and it's also a cool way to tease your friends! They will probably have no idea how you put the ball inside the cube :)

crabapple0001 (author)2016-01-31

Good job.

Thanks for the matches & science lesson, for us slower persons.

stechi (author)2016-01-30

Nice Job! I did a smaller one in response to "Impossible marble in Truncated Cube" and I found I didn't need to soak the wood, I just used a vegetable steamer, and it didn't take long, I think it just needed the heat to soak through. I think it is probably better for the wood if water doesn't soak in too much.

functionaldesign (author)2016-01-29

Interesting project and very nice instructions and pictures!

sdoolan (author)2016-01-28

to prevent cracking, did you. push against the grain?

tomatoskins (author)sdoolan2016-01-28

I can't believe that I forgot that important bit of information! Make sure to press it through the end grain of the cube. I have edited the instructable to make that step easier to understand.

KenW114 (author)2018-01-03

very good

SydneySERS (author)2017-08-15

I wish it stayed in and works inside of it.

actuonix (author)2017-01-04

This is amazing!

dreamitbuildit (author)2016-12-07

have you actually used liquid ammonia as my brief research does not show household ammonia will do anything. The bending forums say it is wishful thinking and that only the ammonia gas is going to work to soften wood. However, for this method ,maybe they are wrong so it would be great to read if betwys1 as found it does work to soak in household ammonia and was it straight from the bottle or mixed with water.

betwys1 (author)dreamitbuildit2016-12-10

I ran tests and deleted my earlier suggestion to soak in 10% ammonia water. I don't advocate soaking in water either. Steam or Ammonia steam is the best way - and plenty of exposure time. I ran tests using iron pipe and found ammonia steam is a little better than plain steam because it reduced splintering. A heater like a camp stove,in a box, heating a pot with a bottle-full of 10% ammonia water heated to boiling. 15 minutes of ammonia steam was enough for lollipop sticks which are thin. Several hours should work for the thicker sections in this trick block

betwys1 (author)2016-12-10

I am presently running tests to optimize conditions for making wood pliable. Not through with this yet, but I can already see that it is better to use steam or gaseous ammonia rather than soaking in water or ammonia solution. In addition, these gases have to penetrate the wood completely to be effective. The thicker the wood, the longer it takes. I find it is not necessary to use bottled ammonia (anydrous ammonia) because 10% domestic ammonia solution can do the job if it is boiled out of solution. Not sure if steam or ammonia is more effective, guessing ammonia, it it is done right

dreamitbuildit (author)2016-12-07

How much work time do you have to get the ball in? How slow do you go? That is, did you tighten ,wait, tighten, or slow even pressure over how many seconds or minutes?

I hope I am clear that I am asking how long it should take to get the ball in as well as how long do I have to work with it?

I am using doug fir as that was what was available and I had one just break on my less hole while the drill press (in 4 places at once) so putting pressure on this will be interesting.

I am soaking now (not sure if that is effective as jayhitek seemed to have failures with even long soaks and boils but I dont know what wood he used. )

So what was the push rate tomatoskins?

If I remember correctly it was fairly slow, but I didn't stop in the middle of it. I didn't time it and I made this almost a year ago so I'm not entirely sure how long it took. I would say at a constant rate. Sorry I can't be of more help than that.

How likely is it the size of the wood vs species. I tried making a block out of white cedar. The forstner bit was requiring too much pressure as it pushed through the interior it took a junk out. I could see it splitting at the spot as the bit was coming down, I just bought the bit and it felt sharp, HOWEVER , my drill press can only do 600 rpm on its slowest and I did read that you need 300 speed for a forstner to work properly,

I think your hole saw was the better solution, especially for end grain.

I wonder if the size of my block matters? My table saw can not rip down a 4x4 to 3" To have clean sides , since flipping did not line up. I end up with a 2 13/16" cube. But even the cedar boiled and still wet from the factory split right open and the ball was not any further .

I do admit, I did not soak for 36 hours. When these cubes split the wood is wet. But is long term soaking the key vs boiling?

I am doing a test of hole size. I have measured and traced the dry cube side, a cube face after boiling for 30 mintues and an over night soak. I have traced each hole and can tell you on white cedar there is no significant change in hole size. I will let it soak to the 36 hours and check again before and after heating it up But I suspect heating it is not the going ot show any expansion, If the mode works it will be the water allow it to compress the fibers and then expand back after not expand the actual hole.

dreamitbuildit (author)2016-12-04

Any idea how much ammonia to water and if soaking does the odor dissipate quickly .

Tried to soak douglas fir over night and can confirm household ammonia does NOT change the elasticity. I even put the cube in a plastic bag and microwaved it for 30 seconds until it was hot. Block broke with first turn of the vise. That is, a slight pressure was needed and I waited a few seconds and could hear it start to split .

This would confirm what I read that soaking in liquid household ammonia will do nothing to help.

betwys1 (author)2016-12-07

Hate it when a tip of mine is found
wanting. My impeccable source was contradicted in numerous places, so I
thought I had better do an experimental check - to get out of the 'He
said - She said' business. I bought two 8in X 1/2 in black pipe, two
1/2 black end caps, a black 1/2 in tee, a black 1/2 in elbow a galvo
bushing 1/2 to 1/4 to suit the 0-200 psi gauge I had on hand. This is
arranged in an upside down ell with a pressure gauge at the bend using
ptfe tape I had on hand..

With a quart of 10% ammonia, the materials cost $11.55

I have a bunch of lollipop sticks on hand as test objects. Here's what I propose:

fill the vertical eight inch leg with room temp water. Place 2 or 3
sticks in the other dry horizontal leg. Close. Heat the bottom cap until
the pressure rises to 25 psi, time it and chill out. Unscrew the top
cap and remove the lollipop sticks.They should be dry. Check the force
to deflect them through 90 degrees.

Then repeat the experiment
with 10% ammonia half filling the vertical leg.Heat as before. Chill
after the 25 psi is reached. Remove the lollipop sticks (outside) as
before and check the force needed to bend them. Do you see any problems
with comparing a brief steam soak with a similar ammonia gas soak?

When I run the test, I'll send details. Here's a picture of the rig hanging off a chair back.

dreamitbuildit (author)betwys12016-12-07

Yes do update betwys1 however you seem to trying to duplicate the ammonia guess method that uses anhydrous ammonia under pressure.

What I question is if bending something is the same as expanding something and would the hole return to the same size or will it stay the same expanded to meet the size of the ball?

My issue with the pine and Doug Fir was that it did what I assumed could happen, since the end grain is the grain, pushing it outward jsut cracked them along the grain. The cube was quite brittle and the hole size did not seem much wider after boiling and steaming.

I am not sure 1 7/8" is a safe size togo with. I am thinking your final photo is maybe not as you recall. I suspect your bit was greater than 2". I dont see how you could have that much more slop with only 1/8" wider hole. Also you still have to get it to expand another 1/4" unless your ball was not 2.25" If your ball is not that size than it might explain some things.

I am guessing cedar and other woods might have different bonds.

I only put a small turn on my vise and in a second or two it cracked and I could easily pop the entire thing open by hand.

I am trying to locate some cedar now.

tomatoskins (author)2016-12-07

I have never done anything with ammonia so I have no idea. I would love to see what your results are!

florinc made it! (author)2016-10-19

Here is my smaller version.

dreamitbuildit (author)florinc2016-12-07

What was was the wood species? I would be curious of the bearing, block and hole size. Thanks.

florinc (author)dreamitbuildit2016-12-07

The cube is poplar, 40mm each side.

The hole size is 28mm. I couldn't measure the ball, but it should be 30-32mm diameter.

dreamitbuildit (author)2016-11-27

How much ammonia to how much water for how long?

offseid (author)2016-10-18

I love any kind of wood puzzle that takes advantage of manipulating the grain. This one was new to me. I would love to try it! Thanks for the great post.

BobM158 (author)2016-07-07

How much Ammonia, and soak for how long???

tomatoskins (author)BobM1582016-07-11

I've never tried using ammonia, but here is a link to a YouTube video that talks about it

Proassault (author)2016-06-29

This is amazing! ...I added this to my favourite ;)

+1 follower

Great job

Logan302 (author)2016-04-28

Wow that is sooooo cool. Very confusing when you see the first pic without reading the ible. Clear instructions aswell. Thanks for sharing

mchau2 (author)2016-02-14

hm, love the match stick gifs, but may i suggest to put a green tick and red cross on the end grain 1 and side grain respectively, so that there is a more clear cut visual cue, i love your style of documentation as is!! great job!!

RaymondC4 (author)2016-02-13

I done this before at school. The only thing is that there's another cube inside it! :D

jayhitek (author)2016-02-03

I love this Instructable. But I had two failures. I made three just incase. I let two soak for 24 hours and boil for 1 hour.
The expansion of the hole must be massive.
For my third attempt I'm going to soak for 48 hours and then boil for 2 hours.
Any advice?

tomatoskins (author)jayhitek2016-02-03

What kind of wood are you using? If your particular wood keeps splitting you might need to make your hole a little bit bigger. I only did this twice. First attempt is shown in the final step and it had 2 inch holes in it (as you can see it left the 8-ball really sloppy). My second attempt I may have just gotten lucky when I went to the smaller hole above.

jayhitek (author)tomatoskins2016-02-08

Another failure for me. This time I soaked for 5 days and boiled for 2 hours.

I not giving up though!

I made one more block and one of the holes is 2"

jayhitek (author)tomatoskins2016-02-04

Or maybe i drill just one 2" hole in the end-grain insertion point..

and then hope no one notices the non comformity..

jayhitek (author)tomatoskins2016-02-04

used cedar. At first I thought it was white ceder. But after I boiled it and it turned red including the water. So I am led to believe it is red cedar.
I will try and make another one today using 2 inch hole saw. Along with a cube that is 3 1/8 by 3 1/8. Maybe that little bit extra will give an appearance of more meat to the wood.

Feb 3, 2016. 7:49 PM

SteveMann (author)2016-02-08

Excellent work, and nice as a sculptural artistic form.

askjerry (author)2016-02-05

My grandfather drilled a hole in a glass coke bottle (Remember them?) and made an arrow shaped piece of wood. He did the same boiling trick... compressed it in a vice overnight, then took out what looked like a flat toothpick and inserted it in the hole of the bottle. Soaking it in hot water again caused it to expand back to original shape. When dry... everyone wondered how he did that.

germap (author)2016-02-03

Thanks for illustrating this so well!

Dawsie (author)2016-02-01

I love these kind of puzzles I have seen the letter E with a nail only in the centre branch of the E through to the bottom branch of the E :-) took me a while to work it out :-) again it's all down to boiling the wood :-)

Thanks for sharing this one :-) will have to see what I can use in place of the 8ball :-)

billtheboomguy (author)2016-02-01

Very nice. Need to try it.

Trask River Productions (author)2016-02-01


george.kriete made it! (author)2016-01-31

First sorry for all the multiple copies of my pictures. I could not remove the duplicates.

Your block looks great. I have a hard time finding quality wood by me. Seems only the two big box stores and a few small lumber yards, but only construction grade lumber.

I have made a diamond in a cube and some different size cube in a cube.

I have also made a golf ball in a cube and a miniature billard ball in a cube. Sorry no pictures of those.

I see you used a hole saw, does it cut better than the fostner bit. they seem to heat up rather quickly. I need to cut slow and let it cool between cuts.

I also noticed you used bees wax to finish, that is what I will try next time. I have used lin seed oil, it smells bad and needs to be reapplied.

Thanks for the pionters and you do really great work.


You will definitely get a better cut if you use a Fostner bit. The only reason I used a hole saw is because I could get one at a fraction of the price. Being a student, every little bit that I can save matters.

ILykMakin (author)2016-01-31

Step 11: Apply "Finnish"

Would it be okay if I applied Swedish or Norwegian instead?


GREAT project. I'm doing this.

About This Instructable




Bio: My name is Troy. I'm a Mechatronics graduate studying Mechanical Engineering. I love making things and doing anything outdoors (especially SCUBA diving). I am ... More »
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