Instructables
Once upon a time, one of my teachers at school brought in a Turner's Cube.  He showed it to us, as well as the cube with a sphere in it.  He was showing things that you could make on the CNC machine, and I thought the cube was amazing.  I knew I wouldn't be able to make a sphere on a manual machine, but a cube within a cube within a cube?  That didn't seem too bad!

And so the quest began!  I began researching Turner's Cubes, and I found information about CNC projects, turners cube calculators, and all that jazz (I even found some that this guy was making on a wood lathe, with all sorts of amazing shapes inside.  Dodecahedron's and the like).  But nothing on a manual machine!  Something had to be done.  I figured out how to make one, made a few prototypes, and once I got a nice one done I came here to share it with you!  Here is an Instructable on how to make a Turner's Cube, on a manual lathe (and mill).  I'll go through the calculations and everything, so you can make one of any size with any number of cubes!

I think this is an appropriate entry for the "Make it Real" challenge, because this is a project that is hardly ever done on a manual machine, it is usually made on a CNC machine.  I believe that making something with your hands and on manual machines  "makes it real" more then programming a robot to make it for you does.  I made models in Google Sketchup and Autodesk Inventor, and have attached the files here.

This project is actually not as hard as it looks, so don't get discouraged by how complex it looks.  Here are the skills you need to be able to make this:
- Working within a +/- 0.005 in tolerance (any more and it looks off) 
- Dialling in a milling machine (to as tight a tolerance as you can get it, 0.001-0.002 is the goal)
- Using a face mill + planar bar on a mill to make the cube
- Facing cuts on a lathe
- Boring flat bottomed holes on a lathe
- Undercutting on a lathe
- Know how to dial in work pieces on a 4 jaw chuck

All in all, this is maybe an 8 hour project.  Once you get all the tools ready, and know what you're doing, it's less then an hour a side. (times 6 sides, and the the time to mill a cube)

Tools/material needed:

- Aluminium stock
- Milling Machine
- 3 in face mill
- Planar bar
- Bandsaw
- Lathe with a 4 jaw chuck (or some sort of fixture to hold the cube, 4 jaw is easiest)
- Grinder (for making the HSS tools)
- Dial indicator with a magnetic back
- Dial indicator with a magnetic base
- Live centre (to set your tool heights to centre)
- Drill chuck (to hold the drill bits)
- Tool holder (for your HSS bits)
- Boring tool for the lathe (I'll show you how to make one out of High Speed Steel (HSS))
- Undercutting tool (again, I'll show you how to make one out of HSS)
- 90 degree chamfering tool (made out of HSS)
- Countersink to reach the smallest hole (5/8, if you use my numbers, if you make your own numbers, you may need smaller)
- Drill bits (to help rough out the bores)
- Files for deburring at the end
- Measuring tools (calipers or micrometers and telescopic gauges.  I like calipers)

 
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jim447210 months ago

Really Nice instructable, can you please explain what a PLANAR Bar is , I haven't heard of it before.

thanks.

Xyver (author)  jim447210 months ago
Planar bar is basicallt a round bar with one edge ground flat.

The flat end rests on the vice, the round end touches your piece, and makes sure that there is only one point of contact, forcing the other side of your work to be parallel with the other side of the vice
gfish1 year ago
You can also make a set of step-cylinders which nest into the bores. These hold everything in place as you do the final undercuts, and generally reduce the risk of damage from clamping forces.
You can make a sphere in a cube... Using an inverse ball endmill plunged from all six sides.
Xyver (author)  Chris Logan1 year ago
I was wondering how to do that... We saw an example of that, but it was made on a CNC. I imagined it was just a small endmill (<1/4 in) and some fancy programming to get the angles required for the circle. But inverse ball endmill would be perfect!

It would still be a bit tricky though, because you'd have to make the hole smaller the the diameter of the ball, and that would make it tricky to get the endmill in.

I may be getting some more time in a machine shop.... Perhaps I should try it to see how it works out.
The endmill dictates the hole diameter.

When I was in machining school (Warren Occupational/Technical Center in Lakewood, CO), we learned to grind the radius into the endmill. The trick, for this part, is to cut a larger radius than the cutter. The resulting ball will be larger than the hole when plunged through from six sides. But will remain attached to small support surfaces at the corners.... This is serendipitous, as you wouldn't want the aluminum ball coming free and bouncing into your fragile cutter anyway.

Once the manual machining is complete, Go back in with a jeweler's saw and free the ball.
Xyver (author)  Chris Logan1 year ago
Ahhh.... But then you'd have rough saw marks on the ball...

If you did plunge in fully on 5 of the sides, on side 6 you could stop, and do similar to what I did in Step 7, for the final side. Just stop the mill, and turn it by hand, so the ball falls off nicely and you dont have to deal with it spinning at upwards of 1000 RPMs :D
If you plunged it completely on 5 sides, you'd have a sphere that isn't very spherical.

You clean the jewelry saw marks up by hand with your trusty needle files and maybe sandpaper. A machinist worth his salt can turn file marks into replica machine-tool marks. I do it often... And polishing the whole assembly to a bright finish is even easier.
ddw_az2 years ago
VERRY GOOD!
i use to do this by hand in Wood.
Xyver (author)  ddw_az2 years ago
Do you have and pictures of wooden ones you could share?
ddw_az Xyver2 years ago
these are my Uncles. My mother has mine
i have done copies of all of these Except the 3-interlocking rings on the left

GEDC0209.JPG
Xyver (author)  ddw_az2 years ago
Pretty wicked! Should try making some of these out of metal
it MAY be possible. I'd love to see it if it is.

however, the wooden models are only possible because of the ability to use a knife and the sheering properties of woodgrain.

One whittles down most of the joint, SNAPS the remaining web, then uses the knife and sandpaper to smooth out the roughness.

To achieve the same results in a machine operation, using metal, would probably require an EXTREMELY delicate bit, a very high rpm machine spindle, and a 5-6 axis machine. The very fine, fiddly work your hands do naturally with a knife blade are impossible to replicate in a 4 axis machine. And nearly impossible in a 6-axis.

Check out the 5:30 mark on this youtube video for the sort of fiddly maneuvers needed by a machine tool to replicate a fairly simple hand-tool woodworking process. http://www.youtube.com/watch?v=GU32Q6QXtWQ




You COULD replicate these in metal, fairly easily, but it would involve casting, not machining.
ddw_az Xyver2 years ago
here are some better photos of the plier joints
untitled.JPG
Looking at this actually makes me giddy. I love it.
This is really cool, I took a manual lathe class as a pre-req for a bunch of engineering classes a few months ago, I think I'll try this.
Xyver (author)  FirstAttempt2 years ago
Do it!
codongolev2 years ago
now I know what I'm making when I gain access to the lathe at my college (and learn to use it). I remember the first time I saw one of these, I just thought and thought and thought until I figured out how it was made. it's shockingly simple, you just need good spatial sense.
Xyver (author)  codongolev2 years ago
Most things are a lot simpler then we think they are. Just take it one step at a time, and before you know it, you're done!
blanchae2 years ago
Little typo: "Male it Real" challenge. Thought that I was reading Cosmopolitan for a minute...
Xyver (author)  blanchae2 years ago
Oh my! Thank's for pointing that out. Fixed!
ironsmiter2 years ago
WONDERFUL!

You beat me to it, but glad to finally see a REAL turners cube!
Not saying the "attached nested cubes" aren't fun to look at, but this requires a great deal more skill. And make better playthings for when you have grandkids.
Also glad to see you did the double nested version(so much more impressive than a one-in-one)


As I understand it, this was an apprentice job way back in the day.
And it was done entirely on a lathe(this being WELL before computers, heck most shops at the time didn't even have electricity!)
It was a testament to the young man's skill, to be able to make the 6 facing cuts, to get a cube. Ok, it was a REQUIRED BASIC SKILL. :-)


Step 11, on the final side cutting... that's an interesting technique!
Sure would have been quicker than how I did it.
I ended up making 5 stepped plugs, with 1-2 thou clearance.(4 jaw chuck, plus a backing plug). Obviously, all 5 plugs were turned on the same lathe.
The main advantage to having plugs is, you can have the machine running the whole time. You don't have to turn the chuck by hand for the last bit. Also eliminated the need for using your shims :-)
Xyver (author)  ironsmiter2 years ago
I'm just finishing up my final project at school, then I'm going to make the "attached nested cubes" (4 cubes) and a free floating one like this, but with 5 cubes instead of 3 :D I'll be sure to add them to this Instructable!
sitearm2 years ago
@Xyver; tweeted! Love the arcane vocabulary (is not a miller) Cheers! : ) Site
Thanks for sharing a very detailed and well presented instructable. though it's rarely done now, it certainly USED to be a very common way for a turner to show his skills. When you talk about using a "manual" machine you are of course only adjusting the machine manually,consider doing the same kind of thing with a "Pole Lathe" or "Treadle Lathe", it HAS been done, but not my me.
Xyver (author)  Dream Dragon2 years ago
I'm mainly talking about manual vs CNC, where we control the machine as opposed to robots controlling the machine.

I can only imagine how tiring a treadle lathe could be.....
you might be surprised how NOT tiring it can be ;-)
I made one of these when I was training. They are quite impressive and I'm still pretty proud of it :)
Thanks for sharing, I hope it inspires people to make one.
rimar20002 years ago
Nice and detailed instructable, thanks for sharing.
Xyver (author)  rimar20002 years ago
Glad you liked it :D