| Established in 1952 | |
Page: 2370 |
An extra feature of two ball couplings is a safety tether consisting of a loop of plastic-covered steel cable that prevents a crash from sending the Ball Bar (Dumbbell) bouncing across the CMM table.
Besides adding the precisely lapped cylinders adjacent to each sphere, the quality of the spheres themselves have been improved by an order of magnitude over the Standard Ball Bar (Dumbbell). The Ultra-Precise Ball Bar (Dumbbell) has spheres which are round and exactly the same size within 2.5 micro-inches (63.5nm). Although sophisticated and very time-consuming laboratory techniques can measure sphericity to a somewhat finer level, 2.5 micro-inches (63.5nm) is generally considered to be the limits of commercial metrology. The surface finish is below 0.5 micro inches (12.7nm). This quality is twice as good as the requirements of ANSI/ASME-B89.4.1-1997 for Performance Evaluating Coordinate Measuring Machines and ten times as good as high quality bearing balls. The absolute size of these Ultra Precise Spheres is held within + or - 0.000020 inch (508nm).
The Design uses unique high strength connections to join the Ultra Precise Spheres to the bar. Computer controlled Electrical Discharge Machines (EDM) are used to drill small diameter concentric holes deep into the already finished spheres. This process uses millions of tiny bursts of electrical energy to erode a hole in each sphere without affecting their original high quality. Both ends of the bar have corresponding drilled holes. As the high-strength glue is applied to the assembly, a steel pin is inserted between these holes to form very strong connections.
In order to provide a stiff, light-weight Ball Bar (Dumbbell) that is still very rigid, the bar is made of 3/4 inch (19.05mm ) diameter steel tubing that has been cold drawn over a mandrell. This steel tubing is electroless-nickle-plated to provide an attractive appearance and to give excellent corrosion resistance.
Because any long gage device is extremely sensitive to increases in temperature through contact with the person operating the measuring machine, a special thermal isolation is provided for the Ultra-Precise Ball Bar (Dumbbell). This is not just bulky insulation, but a series of insulation, isolation and then insulation again. This protects the Ball Bar from dramatic increases in length which would normally be caused by brief contacts with the human operator.
A finished inventory of the 14 most popular lengths of Ultra Precise Ball Bar (Dumbbell)s are maintained in stock for immediate shipment.
We maintain an inventory of stock component parts to quickly produce custom lengths of these Ball Bar (Dumbbell)s. Individual Ultra-Precise Balls or matched pairs of these balls are sold separately for those who may prefer to produce their own Ball Bar (Dumbbell)s or other special calibration devices (See Technical Data Sheet CMM-8, Pg.1 and 2).
Each Ultra Precision Ball Bar (Dumbbell) is shipped in an individual plastic tube case for permanent protection.
Each of our Ball Bar (Dumbbell)s is assigned an individual serial number that is permanently stamped into the bar.
A general certification of conformance stating the nominal size and roundness of the spheres is supplied with each Ball Bar (Dumbbell) at no cost.
An individual inspection certification that is traceable to the National Institute for Standards and Technology giving the exact size of each sphere is available. Their sphericity is documented with an individual polar chart recording. The nominal center to center distance between the Ultra Precise Spheres of the Ball Bar (Dumbbell) is documented.