Hill Cox 0000-00-00 00:00:00
CALIBRATION: YOU GET WHAT YOU PAY FOR BUYER BEWARE: NOT ALL CALIBRATION REPORTS ARE THE SAME. The title for this column would seem self-evident— pay less, get less. However, too many people believe someone offering calibration for well under market price can provide the same level of competence and detail as their more expensive competitors. Many buyers consider calibration reports to be the same with price or delivery the only differences between them. This is not the case when you consider how lower prices come to be. Here are some of the shortcuts that are taken when prices become more important than competence. • The lab in question is not accredited to ISO 17025 by a reputable agency. This saves the lab money, but when it comes to competence, you’ll have to take its word for how good it thinks it is. • No data, just opinions; for example, pass or fail. Until recently, a calibration report did not have to show data as long as it was available on request. This meant that a lot of reports were next to useless. Without the data, customers had no way of knowing the actual state of their gages or how many features were actually calibrated. By the end of December of this year, all A2LAaccredited labs will have to show data on their reports or the reports will not be accredited. Most other accrediting agencies are changing their rules as well. • Sometimes labs put so little data on a report that it means little. An example is reporting a reading from the front and rear of the go gage member, eliminating one in the center to reduce costs. If the reading at the front was undersize and the one at the rear is just inside the top limit, one could assume the gage is badly tapered. If there was a reading in the center and it was the same as the rear reading, a different picture emerges. On thread gages, some labs only report one or two PD readings, and ignore the major diameter. The low cost is obtained through a low level of information. • One way to offer cheaper calibration on new gages is to offer a certificate instead, one that may use data from the shop floor. You’re basically paying for a typing service. • Certificates of compliance or conformance are often substituted for proper calibration reports and auditors often accept them. These are the ultimate cheap report since they aren’t a report at all. In fact, such documents were never intended for use with gages. They are so useless, most companies give them away. • A major cost for calibration laboratories is the equipment required for the work being done. Cost cutters can reduce this by using equipment that is not as good as it should be. If the lab is not accredited, and no statement of measurement uncertainty is provided, you’ll never know if the equipment and/ or masters being used are suitable. The only way to protect yourself is to visit the lab to see what equipment is actually being used, however, even this may not be enough. I know of one gage maker that had a “lab” with all sorts of fancy equipment in it but a warning on the door prevented visitors from going inside. You could watch from the windows, of course, and might actually see someone in there on occasion. Had you been able to go inside, you would see that the room was decorated with unworkable equipment that could not be used for anything except to impress visitors. The actual calibration was done elsewhere in the plant. A reputable gage maker bought out the company and is doing things the right way. But similar dog and pony shows pop up from time to time on a smaller scale. • Another cost component for those who calibrate a lot of gages are the standards they are made to. Cost cutters don’t bother buying these documents from the creators of them and use secondhand material or rely on computer programs which may not match the original data. Where threads are involved, up to 14% of the numbers generated by a computer program will differ from the published values that are the only correct ones. Pay less, get less. Can you afford to save, say $10, on the calibration of a gage that will be used to verify $20,000 or more in component parts? It’s a gamble to be sure. Do you feel lucky?
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