Why do you use different letters on the pins?
The different letters marked on the bags of pins simply designate the sum result of the quality control criteria by which the pins are sorted. In fact, e ach individual pin is tested and retested to verify its performance. Each letter designation of the pins has its own chart so it will provide the same results with very minor differences - differences that are smaller than the operator's ability to measure.
What do the letters mean?
The letters are arbitrary designations to distinguish the groups described above. I've used one letter pin in the past, can I use a different letter pin now?
Users can always change from one letter designation to another as long as they use a chart with the s ame letter that goes with those pins. * Why is a specific letter of pins no longer available?
When the pins are made, each batch may contain pins that end up almost exclusively within one letter designation.
When will a certain letter of pins be available again?
There is no way to predict when a certain letter designation will be produced - in the next batch or following ones, and then again, it should not matter.
* There is one circumstance where using different letter designations of pins may appear to make a difference: When the samples being tested have a hardness right at the edge of their specification limit rather than clustering nearer the center of the spec range. A circumstance can arise where one letter-designated pin may provide a result that is just inside the Brinell spec limit while a different letter-designated pin will provides a result that is just barely outside. Given the reality of Brinell testing, it is just as likely that both these results may be good, or they both may be bad, since the operator is rounding the measurement result, typically to the nearest .05 mm. and typically the impression is created on a surface cleaned by grinding which makes measurement more difficult.. It has been well-established in studies that judgment error reduce the accuracy even more than the rounding of the measurement. The solution to this problem is better surface preparation at the test position and measurement with a more precise scope, like the Newage BOSS Brinell scanner. This will provide a measurement that is more precise than the .05mm interval of the chart and the operators can interpolate a more accurate result.
Also remember: The Pin Brinell is not actually doing a Brinell test as prescribed in ASTM E10. The displacement to load ration is the same, but the load in the impact model is applied much faster which may affect the results. The test itself is not as accurate as the standard E-10 test, although it falls within the range allowable for portable units. In cases where there are unusually tight precise requirements it will be useful to make comparisons between Pin Brinell results and standard Brinell results on the materials being tested in order to verify the capability of the Pin Brinell tester.
There are usually other factors involved when users suddenly discover they are not getting correct results. Thousands of these units are in use around the world so their capability has been well established. Users should try replacing the indenter, CP3 or CP3A, or using another penetrator holder, CP1. These parts will wear or break during use and this will cause an increase or decrease in force to the indenter and result in inaccurate results. Also, the correlation testing should be done on some materials not specified in the conversion chart.
Please refer to the instructions on the reverse side of the pin chart for more information |
