| Established in 1952 | |
Page: 1510 |
| Technical Data Sheet: CMM-18 |
|
|
A Ball Bar (Dumbbell) consists of two very precise spheres of exactly the same diameter securely attached to the opposite ends of a rather long rigid bar. Invar® Ball Bar (Dumbbell)s with their ultra low rate of thermal expansion have long been used in Coordinate Measuring Machine research, but until now they have been far too expensive for general use. The 36% Nickel steel alloy known as Invar has a coefficient of thermal expansion of 0.68 microinches per inch per degree Fahrenheit. This is about one tenth that of steel and one twentieth that of aluminum. It is the lowest rate of thermal change of any commercially available metal. By purchasing the material in entire mill run volume and dedicating our company to serial production of Invar Ball Bar (Dumbbell)s, we have brought the Invar Ball Bar (Dumbbell) price down to a level for everyday use. |
The actual change in length of a Ball Bar (Dumbbell) with a given variation in temperature is affected by three factors:
The first factor is the Coefficient of Thermal Expansion of the material that the Ball Bar (Dumbbell) is made of.
The second factor is the length of the BallBar being measured. The longer the Ball Bar (Dumbbell), the greater will be the change in length.
The third factor is very subtle but it is just as important as the other two. This is the speed at which a material exchanges heat with its environment. Aluminum exchanges heat very efficiently, so it changes dimension quickly. Invar, on the other hand, does not exchange heat very efficiently at all, so it is very slow to move. This phase lag gives the calibration technician more time to perform the multitude of measurements required before even that very small changes in dimension actually take place. In addition, any short lived ups and downs, referred to as perturbations, in room temperature will be factored out entirely.
Using a Ball Bar (Dumbbell) with a low rate of thermal expansion is important, because such long dimensions are involved. Also, the long time period of well over an hour that is required to measure the Ball Bar (Dumbbell) in all of the 20 to 35 positions required to meet the ANSI-B89.4.1-1997 specifications for "Methods for Performance Evaluation of Coordinate Measuring Machines".
The Invar ball bar price is $100.00 more than the standard steel Ball Bar.
| Part # | Description | Price | Purchase |
| PBB-INV-100 | BALL BAR, PRECISION, INVAR 0100 MM, 3.937 INCHES | $330.00 |  |
| PBB-INV-200 | BALL BAR, PRECISION, INVAR 0200 MM, 7.874 INCHES | $370.00 | |
| PBB-INV-300 | BALL BAR, PRECISION, INVAR 0300 MM, 11.8 INCHES | $375.00 | |
| PBB-INV-350 | BALL BAR, PRECISION, INVAR 0350 MM, 13.779 INCHES | $375.00 | |
| PBB-INV-400 | BALL BAR, PRECISION, INVAR 0400 MM, 15.748 INCHES | $386.95 | |
| PBB-INV-450 | BALL BAR, PRECISION, INVAR 0450 MM, 17.7 INCHES | $386.95 | |
| PBB-INV-500 | BALL BAR, PRECISION, INVAR 0500 MM, 19.685 INCHES | $389.87 | |
| PBB-INV-550 | BALL BAR, PRECISION, INVAR 0550 MM, 21.653 INCHES | $389.87 | |
| PBB-INV-600 | BALL BAR, PRECISION, INVAR 0600 MM, 23.622 INCHES | $397.75 | |
| PBB-INV-650 | BALL BAR, PRECISION, INVAR 0650 MM, 25.59 INCHES | $397.75 | |
| PBB-INV-700 | BALL BAR, PRECISION, INVAR 0700 MM, 27.559 INCHES | $401.85 | |
| PBB-INV-750 | BALL BAR, PRECISION, INVAR 0750 MM, 29.528 INCHES | $401.85 | |
| PBB-INV-800 | BALL BAR, PRECISION, INVAR 0800 MM, 31.496 INCHES | $471.13 | |
| PBB-INV-850 | BALL BAR, PRECISION, INVAR 0850 MM, 33.464 INCHES | $427.70 | |
| PBB-INV-900 | BALL BAR, PRECISION, INVAR 0900 MM, 35.433 INCHES | $427.70 | |
| PBB-INV-950 | BALL BAR, PRECISION, INVAR 0950 MM, 37.401 INCHES | $440.63 | |
| PBB-INV-1000 | BALL BAR, PRECISION, INVAR 1000 MM, 39.37 INCHES | $441.00 | |
| PBB-INV-1100 | BALL BAR, PRECISION, INVAR 1100 MM, 43.307 INCHES | $540.63 | |
| PBB-INV-1600 | BALL BAR, PRECISION, INVAR 1600 MM, 62.992 INCHES | $578.23 | |
| < CMM-17, Archival Ball Bar (Dumbbell) |
