Bal-tec™ Home 3D Scanning Master Sphere Set
This set of Master Spheres, consists of five pieces of 5.00 inch (127 mm) diameter, precision ground, satin finished, solid aluminum balls. This set of master spheres is our Part number 5-OS5-AL. This set includes a heavy duty case. These master sphere are also available individually as our part number OS5-AL (without a case) The sphericity of these balls is held within 0.0002 (0.005 mm) maximum, which can be traceably certified to N.I.S.T. (National Institute of Standards and technology).
The electro mechanically etched surface of these balls provides the optimum optical properties, while maintaining near perfect sphericity and dimensional size. The nominal size of these solid aluminum balls is held to 5.00 inches plus or minus 0.0005 inch (0.0125 mm). The absolute size of each individual ball can be calibrated with a long form certification that is traceable to the National Institute of Standards and Technology (NIST).
One of these solid aluminum balls weighs only 6 pounds 4 ounces (2.8 kg). These balls are solid aluminum, so they can not be dented as the hollow plastic and thin aluminum will. These balls are almost indestructible. There is a three eights of an inch (0.375”) [9.5mm] diameter threaded hole machined in the ball. It has 24 threads per inch. This threaded hole is machined perpendicular to the spherical surface, i.e. concentric to the spherical outside diameter. This threaded hole is one half inch deep. See Figure #1
The aluminum ball material is not hygroscopic, so it will not change size with variations in the moisture content of the environment, as plastic balls do. The 12.4 micro inch, per inch, per degree Fahrenheit, thermal coefficient of expansion and contraction of this aluminum ball is consistent throughout the ambient temperature range. This is unlike most plastic materials, that expand and contract orders of magnitude more.
The good thermal conductivity of aluminum brings instant thermal equilibrium of these balls, unlike plastic materials. Temperature compensating these balls for the finest measurements possible is a simple matter of addition or subtraction. In order to assure traceability, each one of these balls has its own individual serial number laser etched around the three eights inch diameter, ( 3/8”, 0.375”, 9.525 mm ) threaded hole.
This five ball set, comes with a set of five lag bolts, that have a three eights inch by 24 threads per inch, male, adaptor thread, that protrudes from the front, to precisely locate the balls against wooden structures. An installation handle is included with the set, to drive the lag bolts. This five ball set, is housed in an extremely rugged, light weight, case that is included with the set at no additional cost. See Figure #2.
A super bonus that you get with this set of five, 5 inch diameter master aluminum balls is that any two of these balls can be attached to a specially designed one meter (39.37 inch) long Ball Bar (Dumb Bell) that is sold separately. This Ball Bar is designed specifically for calibrating optical scanners. This specially constructed Ball Bar is our Part number OS-BB 4000 for the standard steel version and Part Number OS-BB-4000-INV for the Invar® version of this Ball Bar. The Invar ball bar has a low thermal coefficient of expansion. This ball bar will give you both legal traceability and the absolute volumetric accuracy of your measuring equipment all according to ANSI B89 and ISO. See Figure #3.