I am asked the question in many seminars "what do you recommend for recall frequencies on calibrations"? The answer can be very simple yet extremely complex. The simple answer is this-I will not recommend any frequency on your recall system. I also do not recommend that a calibration laboratory suggest recall frequencies for you either.

 Why? Because you are responsible for any product that may have been measured and accepted using the instrument that just failed calibration. It would not be fair to have someone else suggest how often to calibrate your gages when you are the one who has the best understanding of the gages use and the conditions under which it is being used.

 So how do you decide on what recall frequency will work? Let's turn to the ISO 100012 for an answer. The ISO 100012 suggest that you consider 2 items when deciding on recall frequencies:

1. Risk of Failure

2. Cost of Calibration

Your initial choice for setting a recall can be based on several factors including:

• Engineering intuition

• Your experience of gage use

• Your knowledge of other users intervals

• Manufacturers recommendation

• Severity of use

• Environment

• Accuracy

• Gage R&R Studies

• Cost

• History of Calibrations

Frequencies can be set using various options:

• CAU (Calibrate after use)

• CBU (Calibrate before use)

• Number of Uses

• Hours

• Days

• Weeks

• Months

• Years

• etc.

When sending gages to a calibration laboratory it is important to specify what recall dates you want on your gages. The laboratory will most likely default to 1 year. This has been spelled out in their Quality Manual. If you want it different than 1 year you need to tell them in writing. The Purchase Order is the best place to do this.

 You can also adjust frequencies based on calibration histories and Gage R&R studies.