Editor's note: This is the final installment in a multipart series focusing on manufacturers doing their own calibration. The series looks at the reasons why a manufacturer might make this choice, as well as some of the considerations that must be taken into account when embarking on this course of action.

When a manufacturer sets out to do bring calibration in-house, one of the fundamental questions to be asked is, "When is the calibration work to be done?"

This question should be a "no-brainer" to answer, one would suppose. Simple answers could include, "When the need is felt," or, "When it is most convenient." Like everything else in life, nothing is what it seems and these two answers are not enough.

There are really two questions to be answered. The first is, "When must the work be done?" and the second is, "When can the work be done?"

The answer to the first question is that the calibration work must be done on such a frequency that there is little or no risk of a worn or damaged gage or tool that would lead to bad work going out the door. A manufacturer who uses an outside calibration laboratory probably has the question of frequency answered. In-house calibration work can entail problems when it is squeezed between regular inspection work.

Once a manufacturer decides to bring calibration in-house, there are some things that can be done to avoid problems. Begin by getting the managers of the various departments together-including the shop manager, the tool room manager, the personnel manager and the union representative-so it can be explained how the calibration process works. The calibration requirements will affect them all and their cooperation is needed to keep the calibration program running smoothly.

The easiest time to calibrate tools is when there is a plant shutdown for vacation purposes. If a manufacturer doesn't have a vacation shutdown, and operators are allowed to use personal tools, operators must be told to turn in their tools to the calibration department before they leave on personal vacation. If this isn't done, chances are those operators will take their tools home or will lock them up in their toolbox, making timely calibration near impossible.

Production people don't want gages yanked away from them for a day or two in the middle of a production run. Often their view is that the quality crowd is "empire building" in doing in-house calibration. When they understand the rationale behind regular calibration and how it works, most operators will be helpful in ensuring the program is successful. Keep them cooperating with the calibration program by giving them a workable time frame for recalling their tools. Instead of specifying tool recalls in terms of weeks, use months.

Review the frequency of in-house calibration based on the working state of the tools when they are calibrated. Following an arbitrary time scenario such as, "All micrometers will be calibrated every six months," may seem an easy policy to set, but without correct review of the tools when they are delivered, in-house calibration may be occurring too frequently for some tools and not frequently enough for others.

One of the storms a manufacturer may have to endure with in-house calibration is centered on the shop floor. A measurement dispute may arise and said operator may claim that the gage or measurement tool is the culprit. One of the "combatants" will appear at the lab door, gage in hand, and request that it be calibrated while he or she waits. They will want the quality department to, "skip the fancy procedures and rituals and just give them the numbers."

It's difficult to convince an upset operator to leave the questionable gage or tool with the quality department for a few hours, or overnight, to acclimatize before it can be calibrated. If everyone in the plant is made aware of the "Hows" and "Whys" of the calibration procedures, it will help avoid statements such as "Hey people, that's what happens with those outside labs. We shouldn't have to go through all that with calibration being done in-house."

The use of control or check standards, can help reduce the calibration frequency and ensure that problems are caught in a timely manner. When people have breathing space, rather than get angry at your calibration department, they will be willing to work with them.

I hope these columns have given manufacturers some issues to consider when deciding whether to bring calibration in-house. With careful planning, in-house calibration can be done as efficiently and as accurately as when done by an outside lab. Implement an in-house calibration program one or two tool types at a time so that the program can be changed as the need arises.