Small Hole Drilling of Balls— Micro Drilling Small Balls

Drilling holes in very small balls has been a major problem, up until now. There have been two approaches to this problem in the past. The first was to mechanically cut a hole in the ball with steel or tungsten carbide drill. There are two problems with this process: first that you could only drill relatively soft materials, and second, you couldn’t hold the ball against the torque of drilling. It only takes a matter of grams of force to permanently deform a small diameter ball.

The second method of drilling small balls was to cut the hole by Electrical Discharge Machining (E.D.M.). This method, where sparks of electrical energy do the cutting, sounds better than it ends up being. Using normal techniques, the voltage required to jump the gap between the drilling tool and the part will damage the ball. In many cases, it will actually incinerate the ball. In addition, the servo mechanisms that control the gap between the tool and the part being drilled simply aren’t sensitive enough to keep the tool from actually touching the ball and causing a short circuit that welds the cutting tool to the small ball. A fundamentally new approach to the drilling process that adds rotational vibration to the process allows the precise drilling of small balls that couldn’t be done before. This allows for more economical drilling of previously difficult to drill balls.

We are now routinely drilling 0.008 inch ( 0.2 mm ) diameter holes in one millimeter ( 0.03937” ) diameter Titanium balls that would literally have incinerated the ball using a conventional E.D.M. drilling process. This hole size is not the smallest that can be drilled and one millimeter is not the smallest ball that can be drilled. We are now able to drill small Tantalum balls, which were previously thought to be impossible to drill due to an oxide layer that forms on this material and insulates the electrical contact with the ball. As you can imagine, drilling small holes in balls of ordinary materials, is now a simple matter.

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