Mechanical Engineering Center's Masterpiece: Square Hole

（English translation 2023-02-07）

A feed-through connection part was manufactured at the request of the Accelerator Laboratory (Fig.1). It is a dumbbell-shaped part with a narrow center with just a screw hole and a hole for venting gas, and looks not so difficult at first glance, but when viewed from the side, there is a rectangular hole that doesn't go through (Fig.2).

If it's made with wood, you can use a chisel to make a square hole using a technique called mortise joint, but this time the material is stainless steel. If it is a through hole, it is possible to make a rectangular hole with a wire cut electric discharge machine (but strictly speaking, a curved surface corresponding to the radius of the wire remains at the corner of the square), but it did not penetrate.

Therefore, the part was divided into two parts, and after electrical discharge machining was performed to form a through rectangular hole (Fig.3), overlay welding was performed (Fig.4). After attaching the two parts, the outer shape was processed (Fig.5). After the finishing process, it's hard to find the weld marks visually, so no one know how it was made.