Caring for your precision measuring instruments

MESCO Metrology team · September 28, 2026

Precision instruments only stay precise with the right care. A few habits before, during, and after each use protect both the accuracy of your measurements and the instrument itself. This guide covers the hand tools we see most often in our lab: micrometers, calipers, Holtest bore micrometers, bore gauges, height gauges, and dial and digital indicators.

For every instrument: after use, check it for damage and clean it. If it’s dropped or knocked hard, stop using it and have it inspected. Store it in a room free of heat, moisture, dust, and oil mist.

Micrometer

Before use

• Turn the thimble through its full range and check it moves smoothly, without catching.
• On digital models, replace the battery if it’s low. When you close the battery cap or output connector cover, don’t trap the rubber seal.
• Clean the measuring faces: close them lightly on a sheet of lint-free paper, then draw the paper out.
• Check zero: bring the faces together slowly, then turn the ratchet stop 1.5 to 2 turns so it clicks and applies the set force. Repeat 3 to 5 times.

During use

• Don’t wind the spindle back past the top of its range. It can damage some digital micrometers.
• If the display shows an error or the count looks wrong, take the battery out and put it back in.
• Protect the spindle from knocks.
• In long sessions, recheck zero from time to time. Heat from your hand expands the frame.

After use

• Check it for damage and clean it. If you find damage, have it repaired or replaced.
• Release the spindle clamp and leave the faces 0.2 to 2 mm apart, not touching.
• For long-term storage, oil the spindle with micrometer oil to prevent rust and take the battery out.

Caliper

Before use

• Wipe the beam’s reference surface with a cloth and a little micrometer oil.
• Slide the jaw along the whole beam and check it moves smoothly, without catching.
• On digital models, fit the battery positive side up. Clean the measuring faces, close them, and set zero.
• Hold the closed outside jaws up to the light. No light should show between them. Check the inside jaws the same way for dirt or burrs.

During use

• Use a steady, even force, and measure as close to the root of the jaws as you can.
• Keep the jaws square to the part; don’t measure with them tilted.
• If it’s dropped or knocked hard, stop using it and have it inspected.

After use

• Check it for damage and clean it. If you find damage, have it repaired or replaced.
• Leave the outside jaws open 0.2 to 2 mm, with the locking screw loose.
• Take the battery out for long-term storage.

Holtest (three-point bore micrometer)

Holtest is Mitutoyo’s three-point internal micrometer for measuring bores.

Before use

• Clean the contact surfaces.
• Turn the thimble through its full range, and check the anvils move in and out smoothly.
• Set it with a calibrated setting ring. If you’ll measure with only the tip of the anvils, set zero at that same point.
• For absolute measurement, enter the setting ring’s calibrated value as the preset.
• Replace the battery when the low-battery symbol shows, and make sure the seal sits properly under the cap.
• Each measuring head is matched to its body. Fitting a different head voids the accuracy specification.

During use

• Bring the anvils lightly into contact with the bore, then turn the ratchet 2 to 3 turns (5 or 6 clicks) for a steady measuring force.
• Protect the anvils from knocks at all times.
• If the display shows an error or the count looks wrong, take the battery out and put it back in.
• Don’t wind the spindle back past the top of its range. Stop if you feel resistance.

After use

• Check it for damage and clean it. If you find damage, have it repaired or replaced.
• For long-term storage, apply micrometer oil to the anvils and contact surfaces to prevent rust.

Bore gauge

Before use

• Clean the contact point and anvil with a dry cloth.
• Tighten the clamp screw to lock the dial indicator in place. If it still moves, clean the gauge stem and the clamp screw.
• Set zero on a setting ring, or on an outside micrometer set to the nominal size. Rock the gauge gently and zero at the turning point, where the reading reverses. A bore gauge checker makes this quicker.

During use

• Tilt the handle as you insert the gauge into the bore or setting ring, so the guide goes in first and then the anvil.
• If it’s dropped or knocked hard, stop using it and have it inspected.

After use

• Check it for damage and clean it. If you find damage, have it repaired or replaced.
• Dry it completely and put a thin film of micrometer oil on the contact point.
• If the contact point is scratched, or you suspect dirt inside the head, don’t take it apart yourself. Send it to our service team.

Height gauge

Before use

• Clean the column, the base’s reference surface, the scriber mounting surface, and the scriber’s measuring face.
• Clean the granite surface plate you’ll use it on.
• Set the scriber as close to the column as the job allows.
• Move the slider through its full range and check it moves smoothly.
• On digital models, fit the battery positive side up. After a battery change, bring the scriber down onto the surface plate and set zero.
• Carry it with both hands, one on the slider and one on the base.

During use

• Turn the feed wheel slowly and keep the measuring force steady.
• Use coarse feed to move quickly (push the handle in and turn the whole wheel) and fine feed for the last approach (pull the handle out and turn the sleeve).
• Don’t let the scriber stick out over the edge of the surface plate.
• If it’s dropped or knocked hard, stop using it and have it inspected.

After use

• Check it for damage and clean it. If you find damage, have it repaired or replaced.
• If it won’t be used for a while, leave the scriber unclamped and just above the surface plate, not touching it.
• Switch it off. For long-term storage, take the battery out and put the dust cover on.

Dial and Digimatic indicators

Before use

• Clean the spindle with a dry cloth or one dampened with alcohol. Never oil the spindle.
• Move the spindle through its full range and check it moves smoothly.
• On digital models, fit the battery.
• When you set zero, push the spindle in at least 0.2 mm from its rest position.
• Line the spindle up with the direction you’re measuring. An angled spindle reads short (cosine error).
• Where there’s a lot of oil mist or dust, use a water- and dust-proof indicator.

During use

• Don’t move the spindle fast or push it sideways.
• Use a stand or holder that won’t flex under normal use, and clamp the lug so the spindle stays square to the surface.
• On a Digimatic indicator, an “E” that flashes at the end of the display while the spindle moves is normal. If it stays on with the spindle at rest, the indicator needs repair.

After use

• Check it for damage and clean it. If you find damage, have it repaired or replaced. Don’t oil the spindle.
• Take the battery out for long-term storage.

Dial test indicator

Before use

• Clean the contact point with a dry cloth.
• Move the stylus through its full range and check it moves smoothly.
• Use the stylus length specified for the model. A longer or shorter stylus changes the reading a lot.

During use

• Use a stand or holder that won’t flex under normal use.
• Don’t take the indicator apart or modify it.
• Set the stylus as close to parallel with the surface as you can. The reading is only true when the stylus is parallel to the surface, so the contact point moves the same way the surface does. Up to 10° off, the error can be ignored. Beyond that, multiply the reading by the coefficient below.

True value ≈ reading × K. For example, a 0.10 mm reading at 30° is about 0.087 mm.

After use

• Check it for damage and clean it. If you find damage, have it repaired or replaced.

Good care keeps an instrument accurate between calibrations. It doesn’t replace them. Have your instruments calibrated on a regular schedule, and see Measurement basics for how micrometers and calipers are checked.

Adapted from the Metrology team’s small tools product training, based on Mitutoyo’s instrument care guidance. Always follow the manual that came with your instrument.