Care and Maintenance of Calipers

Imagine this: You arrive at work to find your best customer has just returned $10,000 worth of precision metal blocks. They arrived with a nasty note saying that they are out of tolerance. You stand to lose one of your best contracts, not to mention your job, unless you get to the problem right away.

Here are some ways to prevent this from happening:

Highlights: Do’s and Don’ts for Caliper Care

The caliper is a precision measurement instrument, so make sure you avoid common mistakes that may damage it or put it out of calibration alignment. Here are a few tips:

Don’t

• Never drop or throw your caliper.
• Don’t lay the caliper on the bench where it can be damaged.
• Don’t lay the caliper in any kind of debris (metal chips or grinding grit).
• Do not exceed the measurement range of the caliper.
• Don’t use a caliper as a substitute for other tools. (e.g., Don’t use a caliper as a pry bar or a screwdriver)

Do:

• Wipe the measuring faces of the caliper and the to-be-measured surface of the work piece to prevent measuring accuracy from being negatively affected by dirt or dust.
• Clean the calipers after use.
• When not in use, be sure to return the caliper to its storage case.
• Only use your caliper on stationary parts.
• Protect your dial calipers from dust which can get inside the dial and cause inaccurate readings.
• Check the caliper’s calibration periodically and follow the manufacturer’s instructions for recalibrating if necessary.

Caliper Care and Maintenance

Calibration

Check the calibration sticker to check the calibration schedule. Make sure that the caliper is calibrated at least once a year and more often according to its use.

Check the Calipers for Dirt and Grime.

After use, it is important that you check for any unwanted residue that may affect the accuracy of the caliper. Prior to measuring, you must clean and dry the surface of the item to prevent dirt, corrosion, or a file of oil which could cause an inaccurate measurement. Clean the surfaces by applying a small drop of oil on the beam of the caliper and wiping with a clean cloth before storing the calipers. A light coating of high grade instrument oil will go a long way to extend the life of the tool.

Wear

Make sure to inspect your caliper for wear and tear such as burrs and scratches on the jaws. The accuracy of the calipers is dependent on the flatness and parallelism of the two surfaces that come into contact with the part. When these surfaces wear, the accuracy diminishes. A caliper has an accuracy of 0.001. The “rule of ten” states that a measurement tool should have ten times more resolution than the tolerance of the dimension.

Proper Storage

Check to see if the caliper is stored with the jaws closed. If there is dirt on the measurement surfaces, closing the gauge all the way grinds the dirt in between the two surfaces. If you have to store these tools for a long period of time, place a silica gel pack in the drawer of your tool box to prevent rusting. Moisture can become a big issue with digital calipers.

Temperature

Temperature has a substantial impact on measuring results. Precise measurement of work pieces should be ideally carried out with the temperature being about 70°F. Since it is not always possible to be in an ideal situation, one can minimize any error by having the work piece and measuring tool share the same temperature some time prior to the measurement. Precision measuring tools should not be put under direct sunshine or any other heat source because accurate measurements will not be achieved as the temperature increases.

Avoid Magnets

Precision measuring tools should never be put near any magnetic material such as a magnetic worktable to avoid being magnetized.

Avoid Errors That Can Cause Inaccuracy in Measurement

Alignment Errors

A caliper is prone to error described by “Abbé’s principle,” which says that a source of error is introduced anytime the reference line of a measuring system doesn’t lie along the same line as the dimension being measured. On a caliper, the scales or gears are not in line with the measuring faces or contacts. As a result, the caliper shifts and wiggles (in microscopic increments) in a way comparable to that of a table or chair when the legs become loose. The error can be minimized by measuring as close to the rail as possible

Errors Due to Vibrations

For consistent and repetitive readings, a gauge should be subjected to as little vibration as possible, or none.

Internal Diameter Measurement Errors

Another error limits the instrument’s effectiveness at measuring an internal diameter. The design of the standard caliper places the measuring contacts or jaws offset from one another. That means the jaws will never “find” the maximum diameter of the work piece.

Advantages of Calibrating Your Calipers

• Provide repeatable accuracy, saving time, money, materials, and labor.
• Calibrating a caliper is the easiest way to avoid errors.
• Reduce the risk of products failing in service.
• Save money from warranty and rework costs.

Tra-Cal Knows Mechanical Measurement Tools

Tra-Cal calibrates a broad range of mechanical measurement tools and equipment:

• Manual tools (calipers, dynamometric wrenches and screwdrivers, torque wrenches, etc.)
• Powered mechanical measurement tools (electric, pneumatics, hydraulic)
• Mechanical measurement meters
• Test benched (meters linked to a display)

Get Your Calibration Quote Today!