Making Large "Turner's Cubes" on an Engine Lathe

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Originally Posted by aaron p

I have a question about the diameters of the circles and depths of each step. How did you figure out the dimensions so that the hole on the neighbor side wouldnt break threw the wall and such. I want to try to make one. If I make one, im freakin framing it and putting it on the wall!
Also, could I just make a fixture that locked into the normal lathe jaws? Say a 6" or 7" piece of stock, face/turn/face and make your same type of clamp system onto that?

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Hi aaron,
One of the best tools at my disposal was two years of College classes in AutoCAD back in thee early 80's! With all the things I design and build, they have all had time in my computers!

With the large cubes, I drew a square, then drew a line connecting the points. then offset the lines .03125" to either side. then I deleted the line in the middle. This was done on both the top and side views. Now on the top view, I drew a circle .25" smaller than the square. With a depth that intersected the lines. then I repeated the processes until the center of the cube was reached!

By doing it this way, the points in the corners became equivalent to a 1/6" pin!

I hope this helps answer your 1st question. As for fixtures, there is no limit to the types and designs you can choose from. My fixture was an attempt to hold a rigid stainless cube, and it actually worked very well for the fragile Acrylic plastic cubes too (except for a little chatter in the surface finish!

Widgit

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Originally Posted by ImanCarrot

I cheated and used a CNC mill to mill the holes out, but the maths is the same- I used.

Bore diameter= 85% of cube face length.
Depth of bore= 15% of cube face length.
Cube 2 face length= Cube 1 face length-(Depth X 2)

This was in acrylic.

I then dyed it black.

Admittedley, it's not a large cube... so when I get some time I'll have a go at this lump of ally :)

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Using the 85/15% math I came up with the following dimensions for a 3" start cube.
Dia. #1=2.55, Depth=.45
Dia. #2=1.785, depth=.315 more than the 1st step. .765" total from the face
Dia. #3=1.2495, depth=.220 more than 2nd step. .985" from the face
Dia #4=.8755, depth=.1545 more than 3rd step. 1.1395" from face
you can go on and on, till there is no meat left. just gets soo tiny, its hard to machine that small. Does this sound right?

The 1st square is 3"
2nd square is 2.1"
3rd is 1.47"
4th is 1.03"

Somebody double check my math please.

Came to this thread from Bob's webpage :)

Metric guy here, I made a solidworks07 model and used the "eye method" to make a 5 levels turner cube (50mm side, almost 2 inches)

http://peu.net/mods/turnercube01

By measuring the highlighted "hypotenuse" (measured the straight line not the arc) at around 3.2mm I was able to calibrate each step.

Then by serendipity I discovered that if you adjust the 1st cut-extrude operation depth all the other depths adjusted automatically to around the same value.
To achieve this I used the bag of tricks SW provides, so instead of extruding each side each time, I made a single side and then it was patterned at the remaining sides.

Here is the SW07 file for those who can open it. Now I need to find some metal/acrylic to try it :)


Pablo

made mine:

http://peu.net/mods/turnercube06

:rainfro:

Hello, all. I believe that this is my first post here.
These cubes got my gears turning, so I did a quick render with my Alibri CAD, and published a 3d adobe of the solid model.

Attachment 80441

If you have Adobe reader, open the file, then click once on the picture. You should then be able to rotate the cube through 3 dimentions.

I got a little carried away with the last two squares, It would be pretty tough to machine; there is only 5 thou of material at the thinnest point of the smallest square, but it looks neat anyway :)

These are all pretty neat.

I remember as a kid my uncle went fishing in Tennessee and purchased a "Tennessee Walking Stick". It had been carved by a local and had 3 - 4 loose balls inside of a rectangular hollowed out area. Basically, he had hand carved the balls inside of the hollow.

The fixed versions of these cubes are quite an accomplishment, but for some reason, I was thinking that it was possible to make the inner cubes "free" but still contained. Is that a misunderstanding?

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Originally Posted by harryn

The fixed versions of these cubes are quite an accomplishment, but for some reason, I was thinking that it was possible to make the inner cubes "free" but still contained. Is that a misunderstanding?

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No, not at all. You have to do what's called an "undercut" to break them loose. I like the geometric precision of the fixed version though.

Cheers,

BW

Whoaaaaaa I made the exact same cubes back in High School (2001)
Nice work! have you seen the one with different shapes on each side? They have:

Square
circle
triangle
four leave clover
Diamond pattern
cross

I never made the base for it, just the cubes.
Any more fun projects to share?

I use this as a comprehensive project for my students. 6-sides, 6-methods as follow: 1. Mill and Boring head, 2. Mill and rotary table, 3. Bore in 4-jaw chuck, 4. G-code on CNC machining center, 5. Toolpath with our CAD/CAM software (Esprit), 6. Conversational program on CNC machining center with mandantory multiple tool changes. If anyone can do all these processes, they can do nearly anything. All this on a 2 1/2 inch aluminum cube. Then just for fun, a 1/8" radius is added to all levels and around all outside edges. This has proved to be a great project that students think is "cool", and not just making parts for the sake of making parts.

Cruncher69,

What level students are you teaching? No one in here said that making parts just for the sake of making them was the way to go. Our high school is richly involved on the annual Robotics cometition held by US first organization. Basically what we do is we build robots, way "cooler" than making a 2 1/2 block with a bunch of operations.

http://www.team207.org/

Making these cubes is just the tip of the iceberg, we also learned how to engrave, make brass darts which covers many of the lathe operations such as drilling, turning, facing, paking paters, making round ends, threading, grooving, facing, knurling... We also learned how to weld, program using G-codes, program our motherboard for the robot, welding techniques, engineer the entire robot outselves, design in CAD, make 3D animations, you name it! Making anything really is learning something, you shouldn't put down this cube project for high school students since that's one of many abilities these young individuals can learn to make.

Hi all,
I know its been three years from the start of this thread, as I've been staring at the large stainless cube sitting on the shelf above my TV! Many changes have taken place in my family; unfortunately, keeping out of my workshop :( and full of stress!
Walking through my garage every day, looking at all my machines just rusting up from lack of use saddens me even more. So I decided to spend an hour a day in the garage to keep my hands busy!

The first project on the bench is a base for the stainless cube, one that has a little 3VDC 15-RPM motor to spin the cube! So I drew up a few sketches in cad, and started making parts!

But first I needed to make a bending jig to make two 5/16" dia, posts which will be welded to the upper bearing. Here is a picture of the bender:

After the parts were bent to an exact 90 deg., I made two small rings and a part to hold the upper bearing.
The upper bearing support had two shallow counter-bores on the sides, which allowed me to place the bent parts in them and in the lower bearing plate. Then I made up a test bar to set the distance between the bearings, and held all the parts together loosely with a rubber band. Now the welder made a tack on the little rings which had slid down to the lower bearing plate. Next the welder put a bead around the ring on each rail.
Before I can weld the bent rails to the upper bearing part, I put the bent rails in the lathe an carefully cut a nice fillet radius in the welds. Then I dialed in the rails so they were straight up to the bend.
After reassembling the parts with the test gage, I returned to the welder to have him finish the upper welds.
Then I spent a few hours filing and sanding the fillet on the upper welds. then I pressed in a new bearing!

Now that the upper bearing support is done, I can work on the lower bearing plate. At first I had turned and faced a piece of aluminum, and put the bores on both sides of the bearings. Then I had drilled the through holes for the upper bearing supports. This allowed me to get everything aligned for welding.

Next, I put the plate back in the soft jaws, and cut a nice pocket on the under side. This made the plate much lighter! Then I put the plate in the mill and drilled & tapped 8x #10-24 blind holes, these will be used to fasten the lower assembly which will contain the motor & gears!

Now for the fun part!
I bought a big chuck of Walnut lumber 2"x12"x12" on eBay, and decided it would make a perfect base! So I scribed a 10 1/4" dia circle and band sawed it out!
Next I faced it flat on both sides, and drilled the 8x holes through the block. I decided that wood is too soft and easily damaged, so I took a 1/4" aluminum plate and sawed the same circle and drilled and countersunk 8x holes.

Next I put all 8 screws through the base plate and the walnut block, and placed the assembly in the soft jaws. Then I turned the base plate true to 10" dia, and turned a 30 deg angle on the walnut!
After sanding the wood, I removed it from the lathe and assembled the whole unit!

Now its time to make the drive & idle points, as I refuse to drill or weld anything into the cubes! If you remember back a few years, I had made a nice punch and guide block to make a three sided divot in a piece of stainless, using the mill's vise as a press! The guide block needed a slight modification, and it was ready for business!

I turned up a couple parts in the lathe, and pressed the first divot in the lower drive socket. Then i placed a small ball bearing in the divot, and repeated the press until the top of the bearing was within .001"

Then I did the same thing for the upper idle divot. Now I had made two other pins with divots in them a while back, and they were also measured with a ball bearing. The allowed me to place the cube in the lathe and hold it between points, where I used the lathe's DRO to measure the distance on the cubes three point sets. They varied only .0005", so the cube can be mounted on any two points without problems.
The measurements also allowed me to get the CAD drawing as accurate as possible!

Now that the cube is mounted securely and spins freely, its time to work on the inside of the wood block. At first I had only removed a small amount of material, so the lower drive shaft could spin freely. The motor mount will be made of black Delrin, around 2 1/4" dia. it will place the motor horizontally at 90 deg to the drive shaft. There will be two small nylon bevel gears attaching the two shafts.
My choices at this point are to bore a 2 1/4" dia hole through the wood and the base plate, and make the motor mount installable from the bottom. Or make the motor mount hidden inside the wood!

The only things which will influence my decision are the choice of using AA batteries or AC power pack! Or both!

Back to the Drawing board!

Eric, so glad to see you're getting back into the shop a little bit. I'm sure most of us wish we could be as productive on an hour a day!

Your cube display looks magnificent. Be sure to put a little spot light nearby. The reflections on the ceiling and the rest of the room should be mesmerizing.

Best Regards,

Bob Warfield

Thanks Bob!
Its good to be back on the Zone, instead of lurking around in silence!
Eric

That there is super cool I don't car who you are....!! Very nice work man. Someday I will get around to trying to make one of those cubes... Really neat.

Peace

Pete

Well it took me a while to do it, but I made a little transmission to make the cube spin!

First I made a black Delrin block that bolts on the bottom of the upper plate, and bored a 7/8" dia cross hole. Next I made a slide out of 303-SS, that fit nicely in the bore. After winning a 56-RPM gear motor that runs on 3-VDC, I bored one end of the slide to fit the motor. Then I made an extension spindle which has two bearings, two spacers, one nylon bevel gear, and a hole with a setscrew to attach it to the motor's shaft.

Then I turned the outside ends of the slide to .75" dia, and made two clamps with long arms. Next I made two 303-SS buttons with 6-32 UNC threads on one end, so they can screw into the long arms of the clamps.
One of the buttons has a 3/64" radius groove, which will trip the micro switch and turn the motor on!

The reason for the over complicated gear box, is that for everyone I had shown my project to, they all smacked one point of the cube to get it spinning! Well, those little nylon gears would not last very long, as the power ratio at 2" from the cube's centerline is more than the little 3/8" OD gear can handle!

So I devised a mechanism which engages the gear as it powers up the motor, and puts the cube in free wheeling mode when power is off!

Now I have ordered two single "C" battery holders, and will have to wait for their arrival before I hog out the inside of the wood! It would be nice to be able to remove a cover plate from the bottom to replace the batteries, so I will try to think something up!

Here is a nice movie of the spinning cube:
VIDEO