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

[Geof]

Very nice job Eric.

But I think it is toss up between the finished cube and the elegant fixturing you built to machine it; both are an impressive example of craftsmanship.

[widgitmaster]

Originally Posted by Geof Very nice job Eric. But I think it is toss up between the finished cube and the elegant fixturing you built to machine it; both are an impressive example of craftsmanship.

Thanks Geof!
I have been thinking of making some cubes out of plastic, or aluminum just so I don't have to toss the fixture in the scrap pile
It was surprisingly rigid, and the lathe was able to repeat nicely!

Widgit

[Geof]

Originally Posted by widgitmaster Thanks Geof! I have been thinking of making some cubes out of plastic, or aluminum just so I don't have to toss the fixture in the scrap pile It was surprisingly rigid, and the lathe was able to repeat nicely! Widgit

Plastic!!! Cast Acrylic.

Make them in cast acrylic, polish all the surfaces optically clear and they would look fantastic. Especially if you illuminated them correctly, you would get a prismatic effect in all directions.

See if you can locate a supplier for blocks of cast acrylic and how much it would cost, I will cover the material cost if it is not too horrendous in exchange for you making me one.


P.S. Never, ever toss a fixture in the scrap...that guarantees you will need it the day after you tossed it.

[widgitmaster]

Originally Posted by Geof Plastic!!! Cast Acrylic. Make them in cast acrylic, polish all the surfaces optically clear and they would look fantastic. Especially if you illuminated them correctly, you would get a prismatic effect in all directions. See if you can locate a supplier for blocks of cast acrylic and how much it would cost, I will cover the material cost if it is not too horrendous in exchange for you making me one. P.S. Never, ever toss a fixture in the scrap...that guarantees you will need it the day after you tossed it.

Now that's a done deal!
As I have already ordered an 8" dia x 7" long piece off eBay!

Two plastic cubes are in the works

Widgit

[widgitmaster]

Ok, I'm totally hooked on this large Cube, especially when its spinning on it's axis!

Unfortunately, my abilities in 3D CAD are nonexistent!

Could some one please tell me what the compound angle is if the cube is rotated 45°, then rotated until the two furthest points are perpendicular!
(The cube measures 3"x3"x3")

I have found some solid Vee Jewel Sapphire Bearings and points, and plan to make a base with a support arm that will allow the cube to rotate like a globe!

http://www.smallparts.com/products/d...ns/vja-hst.cfm

But in order to install the Sapphire Bearings, I need to position the cube with its point upward.

Widgit

[DR-Motion]

Hi Mr. Widgit,

I'm not sure which compound angle you are referring to; but the diagonal distance across the face of a cube is Square root of 2 times the length of the side, and the the diagonal distance from the most opposite vertices is Square root of 3 times the length of the side.

In your case the distance between the mounting points ( assuming no radius) is 1.732 x 3 inches = 5.196 inches.

hope this helps.

regards Gary

[widgitmaster]

Sorry,
Knowing that dimension does not help me setup a compound angle plate on my mill, in order to hold the cube in position for drilling a hole in the center of the point to insert a bearing!

Widgit

Originally Posted by DR-Motion Hi Mr. Widgit, I'm not sure which compound angle you are referring to; but the diagonal distance across the face of a cube is Square root of 2 times the length of the side, and the the diagonal distance from the most opposite vertices is Square root of 3 times the length of the side. In your case the distance between the mounting points ( assuming no radius) is 1.732 x 3 inches = 5.196 inches. hope this helps. regards Gary

[BobWarfield]

Widgit, sorry, while I was drawing this you were explaining what you really wanted.



I literally have to run out the door, but I'll pull the compound angle when I get back if nobody else has posted.

Sorry!

BW

[widgitmaster]

Now that's a Warfield to the rescue

[Geof]

35.26 degrees????

Better wait for Mr Warfield, I have more faith in him than my trigonometric ability.

[widgitmaster]

I keep getting 90º 55º 35º

Base = 4.2526, Height= 3.0, Hypotenuse = 5.1961

I'm anxious to get the cube spinning, and those sapphire bearings look really interesting!

[BobWarfield]

Okay Mr Widgit. I got my cube up on end with 2 rotations. The first is a 45 degree rotation around Z. The second was not intuitive, so I'm glad I could let the CAD program figure it out. It worked like this:



Geof, congratulations, you have essentially the same angle just from a different normal as the two sum to 90 degrees. I think I read somewhere that you do all your CNC programming without CAM? You definitely have some geometry skillz to do that, my friend! I'm too dumb (or too lazy) to do all that in my head. I kept wanting to visualize 2 45 degree rotations, but that 2nd rotation just ain't 45.

Now I can do this stuff in CAD, but I can only assume what magic the Widgitmaster must use to make that happen on his mill. I'm thinking 2 sine bars or other angle blocks?

Use the first to rotate the cube 45 degrees around Z, perhaps on a fixture plate of some kind. Now use the second to kick it up 54.74 degrees and you have it.

Does that work? I know you've gone to bed in Florida, so I hope I can see the exciting conclusion in the morning. I know you'll publish a fine photograph of the fixturing/setup, and you know that photo will be appearing in the CNCCookbook.

I agree, those saphire bearings are very cool. I can't wait to see your display stand, Mr Widigt. I know it'll be a gorgeous piece of art that I will be lusting after.

BTW, I don't know if you liked the dodecahedron I showed, but I would think making each solid would also be an interesting set of projects to display. I suspect intuitively (but I have had a drink or two this evening!) that you could take your boring bar to each face of the dodecahedron and create quite an amazing Turner's Cube the likes of which has perhaps not been seen before. Dodecs within dodecs. Think what a tasty fixturing problem that would turn out to be!

But we digress. I eagerly await hearing whether this helps, or if I need to get back in my CAD program and figure something else out.

Best,

BW

PS I am finally taking my first baby steps towards converting my mill to CNC. I can't stand being able to make all these drawings and then having to bring them to reality by hand!