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Thursday, January 22, 2015

Cube Twist

A few months back, I finally finished a bottle opener for my old man (pictured below) using a technique called a Cube Twist or Rubik's Twist. While very simple to do technically, the result is disproportionately alluring. After making the bottle opener, I had a number of people request information on how I did it, so I decided it is easier to show through pictures than through words.

First and foremost, having a square cross section is critical for a cube twist (it can be done with rectangular or other shaped cross sections, but that will not result in a cube twist). For this particular project, I have a tapered, square pyramidal shape, but it is easier if the entire length of the cube twist is the same size, which makes the final step- twisting- easier.

I added a little bit of decoration to the top end of the stock which will eventually become a glass cutter.

This is where the cube twisting begins. After having as perfectly square a cross section as I can forge, I took the ANNEALED stock over to the bench. Annealing is critical unless you want to burn through half a dozen hacksaw blades if you are using hardenable steel. Wouldn't hurt for mild carbon stuff either, but this was W1 if I remember correctly.

First step is to cut a groove down the centre of each face, starting and ending at the same spot for each of them. Aligning the ends is important for later. A hot cuter can be used, or a dremel or the like, but the narrower the cut the better, especially on thin things like this. You can see that the cut wandered a little near the tip, but as long as it is close and a non jagged transition, it doesn't make that much of a difference.

Cut about 1/3 of the way through the piece on each of the four faces, but no farther than half (as it would meet the other cuts and make the cube parts impossible).

Using a pair of callipers or eyeballs, whichever are closer, measure the thickness of the stock from the corner to the closer edge of the groove. This will be how far apart each of the following cuts will be, making cubes. If that doesn't make sense, look at the next few pictures.

First, cut across one of the corners at the end of the grooves. If they are aligned properly, the three cuts (one from each face and the third down the corner) will all exactly meet. Next, repeat the cuts down the length of the corner until you reach the far end of the groove. With a constant width cross section, the spacing will be the same, but since I have a tapered shank, the space between each cut became steadily smaller to maintain squares.

Here is one side done. Notice how each of the cuts across the corners come down to the grooves? The farther down you can bring them the better, as long as you do not cut too far and mark he other side of the groove.

Half way there. For the next set of cubes, turn the piece over and cut the same pattern on the OPPOSITE side. The result should look something like the above. For the best effect, there should be the same number of cuts on one side as the other. If you are using a pair of callipers, that will happen naturally. If not, just mark them all first before making the cuts. An easy to lay the cuts out first is to cover the surface with soapstone. The white makes it easy to mark with a scribe or something.

Now where the magic happens. Heat the piece as evenly as possible assuming a uniform thickness. Twisting happens easiest where the metal is hottest, so an even heat makes an even twist. Because I have a taper, I had to heat the thick end far more than the thin end, and do it in steps. If you have never done any twisting before, play around with it first on something you did not take an hour to cut nicely. I use a pipe wrench with the teeth ground off to twist things, which does not leave any marks on the steel.

Action shot.

And here is the final result. One cube twist. If the steel bends a little, use a wooden mallet to coax it back to straight so as not to damage the crisp corners. All said and done, it took around an hour and a half to make, including forging the original shape, taking the pictures, and hardening.

Below is the bottle opener which started it all-

Happy twisting!

1 comment:

  1. Thanks. I was long time curious how this shape is don. GT