Drilled and Threaded Balls

There are many applications where a ball with a threaded hole in it would solve a difficult problem. The most common use for a threaded ball is to simply hold the ball rigidly on to a mating part. This is common practice for holding spheres used to calibrate coordinate measuring machines and machine tools.

Another gage oriented application is to hold a hard steel or tungsten carbide ball on the measuring tip of a dial indicating gage. The threaded hole can be machined by conventional drilling and tapping methods, in plastic, mild steel, brass, 300 series stainless steels, and other unhardened materials. For the threading of hard metals such as hard steel, and even tungsten carbide, the Electrical Discharge Machining method may be used. This process uses electrical energy in the form of millions of tiny sparks to literally erode the thread form into a pre-drilled hole. Although little known and seldom used, the newest computer controlled E.D.M. machines have helical path interpolation that allows reasonable quality threads to be economically produced in even the hardest metals. Threaded holes that are a reasonable diameter in relation to the diameter of the ball can be E.D.M.’ed into an ultra precise ball with no degradation of the ball’s original quality.

The pitch diameter of a threaded hole can be machined very concentric to the axis of a ball. In the kinematic coupling arena, the truncated and threaded ball is one of the most stable and easiest to install devices. To attach ceramic balls with a threaded fastener, the ball is first drilled to produce a blind hole. A threaded bushing is then glued in the hole, and it is ready for service. The sophisticated E.D.M. process is not terribly expensive, so minimum quantities can be produced economically. A ball with a threaded hole, mounted in a spherical cavity, and held in place with a threaded fastener is an effective mounting technique that is quite economical. We stock a limited number of drilled and threaded balls. Please see our Kinematic Catalog #105B on this web site for many different sizes and designs of off-the-shelf drilled and threaded balls. Please see our Shopping Cart for stock available on hand.