Fun with Wire EDM

I love metal mechanical puzzles (Wil Strijbos’ and RD’s for example) and I’ve designed a few of my own as well (and I promise my Model #357 will ship this year come hell or high water!) So over time I’ve become familiar with machining processes and the tolerances they can hold since they’re the key to making a metal puzzle with a good feel. A few years ago I came across a super expensive but incredibly cool machining process called wire electrical discharge machining or “wire EDM”. It basically uses a voltage potential between an expendable wire and the metal piece that’s being cut to ionize the dielectric in between (usually deionized water). The resulting plasma erodes both the wire (which is constantly renewed from a spool) and the metal piece. Amazingly, wire EDM can hold tolerances as tight as ±0.0001”.

For several years I’ve been wanting to get a hold of anything made with this process to see first hand how such high tolerances feel. For example, Metmo’s Mk3 Steel Metmo Cube looks incredibly cool but they sell out almost instantly and the $300 price is steep. Lucky for me, I found a source for a puzzle cube made from stainless steel using wire EDM. Here it is:

It is a stainless steel cube about 1 3/16″ on a side. The pieces fit incredibly tightly together and slide beautifully with no side-to-side give. The four puzzle pieces are identical so you could reassemble them in lots of different ways if you wanted. The top and bottom of the cubes were brushed after assembly and the subtle differences in the brush marks let you reassemble the pieces as they were originally configured.

I’ve put these up for sale on my Etsy store in case you’re interested in getting ahold of one. I include a black cubical box that snugly holds the puzzle cube and together they weight a little less than 8 ounces, which has a nice heft. Here’s a video I made of it: