I have personally heard many opinions on this topic and a lot of times, customers default to having their tools recertified every 12 months. However, how often you need your tool recertified really depends on how often they are used and what the operator’s expectations are regarding the accuracy of the tool. If you are going to use your tool once a month or so, then I would suggest that you stick with a once a year recertification schedule. If you are using your tool frequently, then a 6-month recertification schedule may be more appropriate. Some of our customers who use their tools very frequently and have high demands on tool accuracy have their tools recertified every 3 months. One very good habit to be in is to compare each subsequent certificate with the one before. If there are inconsistencies or trends towards under performance, it is a good idea to consider the time between certifications and consider certifying your tool more often. Finally, if your tool ever undergoes repair work which causes the main seals to be changed, then it should be recertified.