The Frequency machines we sell should not need calibration. However, over time the clamps could loosen, depending on how much you use it, and that can effect the readings. If you are getting questionable readings, you can send it to us and re can re-calibrate. That would be the least convenient, I know, but the best way to insure it is reading properly. If we know which machine you have we could possibly talk you through recalibrating yourself, but you would need a shaft or club that is in fact a “recalibration stick” you can use. If the machine is working properly now, take a shaft and clamp it in as you normally would, put the weight on the tip end and take the reading. Mark the shaft with that reading and now you have a calibration stick. We sell a calibration stick for $124.99, but unless you do high volume I am not sure it is worth that spend. If you believe it needs recalibration and want to send it back, just call our customer service department and they should be able help you. If not, let me know. By the way, like the bevo88 tag. Assuming your a Longhorn. My home state and big Longhorn fan living up here in Buckeye land. Hookem! If your not, sorry for the assumption.