Instructables
Picture of Turner's Cube - A Beginner CNC Milling Project
The Turner's Cube we are going to make is an interesting little project that originally came from beginners learning to work in the metal shop. The seasoned old veteran or shop owner would hand one of these to a new apprentice and tell him to figure out how to make it and reproduce it.

For me it was a fantastic first project on the Tormach CNC Mill at the TechShop: http://www.TechShop.ws

In this instructable you will learn how to make a Turner's Cube and in the process practice your skills and precision needed to tackle much more difficult projects and open the doors of all the incredible things you can make using a metal mill.

Tools Needed:

CAD program
CAM Program
Metal Bandsaw (horizontal and/or vertical)
Drill Press
Metal Scribe
Square or Center Finder (ruler works fine too)
Calipers
CNC Mill (Such as the Tormach 1100 at the TechShop)
1/2" End Mill bit
1/2" Parallels
2"x2" cube of aluminum




For my tutorial on designing the cube in AutoDesk Inventor 2012 go here: http://www.instructables.com/id/Turners-Cube-Designing-in-AutoDesk-Inventor-Pro/
 
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Step 1: Step 1 - Creating a perfect cube

Picture of Step 1 - Creating a perfect cube
finding center.jpg
The most important and often most challenging step of this process is milling a perfect cube.

The tolerance for the cube must be within .01 inches or it will be visibly off.

Cutting the blank

First get yourself a chunk of aluminum. It can be just about any shape but you will need to get it roughly to 2"x2". This can be done with a horizontal and or vertical bandsaw. I started with a 4"x8"x2" blank and made one cut on the horizontal band saw and then again in half on the vertical band saw.

The more care you take in getting it cut at straight right angles the better for later on.

Measure the blank with calipers and get a rough idea of how long each side is.

Facing the cube

This was the trickiest part for me; measure twice cut once!

I started off spending a lot of time learning how to zero all the axis of the Tormach. This should be included in the introductory class from the TechShop and you should already be somewhat familiar with this process. Be sure to check both ends of the vise for being at Y0.00  I try to get within .003 inches to be sure my precision is good enough. Don't forget to account for the width of the edge finder when finding zero (0,0).

Find the two surfaces that are the most parallel and put them against the faces of the vice. Below the piece I used a set of 1/2" parallels. At this point it wont make much difference and just about none of your faces are square yet.

Find your Z zero by starting the spindle and lowering it close then jump stepping till the bit cuts in. I used .002 steps here. Zero out your Z axis. Remember EVERY time you reset your piece in the vise you need to find your Z axis zero again. If your face is closer to finished you can lower the bit without the spindle moving till a piece of paper no longer slides between your piece and the bit, then set it at .003 (the thickness of a piece of paper)

Using the jump step settings on your CNC Mill bring your spindle about .05 below z0 and start to face the top of the cube. I would usually bring the bit left and away from my piece, use the Gcode g0z0x-1y0 to bring the bit to z0 then I would set the jump step to about .05 and jump down one step so you are at z-0.05 then set the jump step to .25 and the spindle speed to 7. Start slow and use the override at 50% and work up from there as you get comfortable. I would  manually move the bit back and forth across the face with my stepover never exceeding .25

Once my top is machined flat, measure the top to bottom and using the same faces that were against the vice, orient the piece bottom up.

Calculate how much you need to take off to get to 1.875 inches (the final thickness of the cube), find zero again and face the surface down at about .05-.1 thickness max depth at a time. Measure twice and be sure you have your math right. Better to face it in a few paths than screw it up now. There is no shame in leaving the cube roughly at 1.925 inches and doing the final dimensions when you are sure you have your cube faces all perpendicular and clean.

Repeat this process until you have a perfectly square cube at 1.875 in choosing the most square sides to put against the vice sides and bottom you can with each face.

Congrats, one of the most challenging parts is over!

Tips

-Use some compressed air each time you reorient the cube to be sure there are no metal chips between the vise and parallels and your cube. Once chip can screw up the entire precision.

-Remember to wack the top of the piece with a mallet after you tighten the vice to be sure the parallels below are held firmly and snug the vise one more time. Several of my mistakes came from the piece moving slightly in the vice when machining.





space12311 months ago
Thanks for posting. This is likely a dumb question, but I have yet to do my first project. Why did you need to use the drill press for the centre hole, rather than centre finding on the piece, and manually jogging the z-axis down in small steps? Thanks!
ravenquest (author)  space12311 months ago
Honestly it was just easier to do on a manual drill press as the center block can become somewhat fragile if you drill those holes last. I wanted to be sure how much pressure I was applying.

It can be done just as easily on the CNC mill though. In the end it came down to how much time I had left on my appointment at the mill.
space123 space12311 months ago
Sorry, I mean using the CNC mill rather than the drill press for the centre hole.
rog88112 years ago
As I have been offered a 3d print for my instructables, I thought of you and this instructable.

I wonder if your files are usable for 3D printing and if so would you mind if I used them please?
ravenquest (author)  rog88112 years ago
The STL would work fine for 3D printing. The only problem is you may need a support structure to make it work.
ironsmiter2 years ago
not to put TOO big a dent in your machining ego(though it is a neat piece of work)

but the turners cubes are nested, FREE MOVING cubes!
http://1stclass.mylargescale.com/abernat/turners%20cube.jpg

It makes for a MUCH more challenging project, thought the techniques used to produce it is nearly identicle.
ravenquest (author)  ironsmiter2 years ago
I've seen them made lots of different ways, free moving and not. I chose to make them solid for my first project since I wasn't prepared for what to do if it broke loose while machining it.

This was the original source I was inspired by:
http://www.cnccookbook.com/CCTurnersCube.html

You can see there are plenty of other cubes there that are not free moving.

As you said, it makes for a much more challenging project. You should post an instructable on how you made your's free moving. I've not really seen any info on how to do that.
powerglitch while posting... hopefully this isn't a doublepost.

Anyhow.
There's really no way to give a hint, without giving the whole thing away.

And since this is instructables, not frustratables...

The trick involves making the stepped plugs BEFORE beginning on the cube.
These plugs hold the inner cubes while you do the undercutting to free them from the outer cube.
A tight fit is needed, but not a pressed fit. 1-2 thousandths should be more than enough clearance.
Sounds like you need to post this one yourself!
Xyver canida2 years ago
Gotcha covered :)

http://www.instructables.com/id/Turners-Cube-Manual-Machine/
TheITSystem2 years ago
I'm inspired. I'm taking the class a week from Monday and looking forward to taking on this project as it is. I have half a mind to print one on the 3D printer just to blow off steam while I'm waiting for the class. I watched ravenquest work through this and like I said, inspired. Great work!
Ambermile2 years ago
Well, free-moving or otherwise, (and I don't see anyone stepping up to do an ible on the "completed" option - plugs or whatever), for a first-off project I think it's a great result and you should be well proud of it.
Skymeat2 years ago
I've been trying to make one of these on my lathe. Getting closer each time. I never thought of making one on a mill. Great looking piece.
very professional! really appreciate your great job!
awoodcarver2 years ago
Wow ...We use to do these in wood when showing at local county fairs with the cubes free inside the others , people would always ask if we made them in 2, 3, or 4 parts and look for a glue joint .... I never would have thought of doing one in metal .....Very nice work
keefo542 years ago
Stepped plugs ...ha ha ha no contest ...when you make the thing on a conventional lathe by hand ...ooooh just like the old days ....you pack the cubes with hard wax or wet tissue and then undercut to release the cubes I'm sorry but you have only done half the work .
If your having trouble about getting it square then leave it 1/2 longer in one plane ,hold it in vice and mill the top and 4 sides let the cnc do the work , then flip it over and remove the surplus 1/2 inch hey presto a cube
stick at it as its far more impressive with loose cubes but your doing well
ravenquest (author)  keefo542 years ago
Well I'd love to see an instructable on that!

Hephaestus2 years ago
I made one of these during my apprenticeship in the early 70s. I used a conventional vertical mill plus a boring and facing head., along with a variety of slot drills etc.. I concurr it is an excellent project and lends itself to CNC very well. Highschool tech teachers should look at the above article..
Roy Maybery
whenu2 years ago
Nicely done but probably more of a test if the whole thing was machined by hand.
twimh2 years ago
interesante proyecto,,,,,,,,,jejeje,,, tu tambien tienes una tormach PCNC,,,,que chido
jeffrey42832 years ago
That's a cool little machining project. I wish we had something in Tampa like TechShop so I could have access to that type of equipment.
mikeasaurus2 years ago
What a neat metal machine project!