Established in 1952 Bal-tec Page: 3420

Time-Saving Ball Bar (Dumbbell) Fixture

Part Number 3B-KM

3B-KM Cmm4a.gif (5394 bytes) Cmm4b.gif (6998 bytes)

The Three Ball Kinematic Platform (our Part Number 3B-KM) can be used with any Ball Bar (Dumbbell) having approximately one inch (25.4mm) diameter spheres. This tool will allow you to evaluate a Coordinate Measuring Machine in one half the time required by conventional means. It does this by reducing the number of measurements that must be taken.

A micro-inch accurate reference datum is created at one end of the Ball Bar (Dumbbell). This fixed reference datum consists of a three ball kinematic coupling mounted on a rugged steel platform. One of the spherical ends of the Ball Bar (Dumbbell) rests in the nest formed between the three high quality stainless steel balls.

The opposite end of the Ball Bar (Dumbbell) can now be swept to describe a micro inch accurate hemispherical shell. While many X-Y-Z positions of this outer sphere are measured, only one measurement for the original position of the reference datum ball is required.

The Three Ball Kinematic Coupling is of unique design. It consists of three ultra fine-grain truncated stainless steel balls that are hardened to 58 Rockwell C for long wear. The precision flat ground bases of the three balls are held solidly against the rigid steel platform from below by three socket head cap screws. These high quality balls are .750 inch (19.05mm) diameter with a blind bottom 1/4 inch (6.35mm) diameter hole, with 20 threads per inch (metric threads will be supplied on request). This design allows the kinematic balls to be indexed to literally hundreds of new positions, thus assuring many years of quality use.

The 4 inch (101.6mm) diameter solid steel platforms is 1-1/2 inch (38.1mm) thick and weighs over 5 lbs. (2.36kg). There is a counter-bored hole through the platform which allows it to be clamped solidly to the CMM table by either a 3/8 inch or a 10mm diameter socket head cap screw. A precision flat-lapped annular ring on the bottom of the platform forms a positive coupling with the top of the CMM table. An attractive black oxide coating is applied to the platform to resist corrosion.

NOTE: We also stock several standard diameters of truncated and threaded kinematic balls which are available separately for your special tooling applications. See our Kinematic Components Catalog #105 (Truncated and Threaded Balls).


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