Vernier Caliper, Plastic

Quick Answer: The Vernier Caliper, Plastic is a sliding caliper moulded from plastic, with a main scale and a vernier scale for reading outside and inside dimensions and depths. A plastic vernier caliper is light, does not conduct electricity and suits first lessons on how a vernier scale works.

Where a Plastic Body Makes Sense

Younger students drop things, and a moulded plastic caliper survives knocks that would bend the jaws of a thin metal one. It weighs little, has no sharp steel edges and is simple to replace if lost or broken, so a class set can be issued to every pair of students for an introductory measurement lesson.

Plastic does not conduct electricity and is not attracted by magnets. That makes it the safer choice for measuring coil formers, wire bundles or components in circuits, and for magnetism practicals where a steel instrument could be pulled towards the magnets or disturb a compass.

The trade-off is stiffness. Plastic jaws flex under heavy pressure and their edges wear faster, so plastic calipers generally have coarser scales and drift out of zero sooner than a stainless steel vernier caliper. Plastic also expands more with temperature than steel. For senior practicals, where readings are recorded to the smallest division, a metal instrument is the sounder choice.

Specifications

Care & Handling

• Use light finger pressure; squeezing flexes the jaws and gives a reading smaller than the true size.
• Keep it away from radiators, sunny windowsills and hot plates, as heat can warp plastic.
• Clean with a damp cloth and mild soap only; solvents such as acetone can craze or dissolve some plastics.
• Retire calipers whose jaws no longer close to zero rather than trying to bend them back.

Classroom Uses

• First lessons on least count, using the caliper beside a plain ruler to show the gain in resolution
• Measuring coil formers, cable diameters and cell sizes in electricity projects
• Magnetism practicals, where a steel instrument would be drawn to the magnets
• Model-making and STEM kit activities where approximate measurements are enough

Why Choose LabEquip

Primary and middle schools, and teachers running large introductory classes, often buy plastic calipers as class sets so that every student can handle one. LabEquip lists this plastic model in the General Lab Products range; tell us the class size through the contact page.

Frequently Asked Questions

Is a plastic caliper accurate enough for school practicals?

It is adequate for introductory work and for learning to read a vernier scale. For senior practicals, where results are recorded to the smallest division and compared with accepted values, a metal caliper holds its zero and scale better.

Why is a plastic caliper used near electrical circuits?

Plastic does not conduct, so touching a live terminal or bridging two contacts with the jaws is not the risk it is with a metal instrument. It is still sensible to switch circuits off before measuring components.

Can it be used in magnetism experiments?

Yes. Plastic is non-magnetic, so it is not attracted to bar magnets or electromagnets and does not deflect a compass placed nearby, unlike some steel instruments.

How do I clean it without damaging the scale?

Wipe it with a cloth dampened with water and a little mild soap, then dry it. Avoid alcohol-based or solvent cleaners, abrasive pads and hot water, which can wear printed markings or distort the plastic.

Why does my plastic caliper not read zero when closed?

Worn jaw tips, a slightly warped beam or grit in the slider can all shift the zero. Clean the jaws and slider and check again; if an offset remains, record it as a zero error and correct each reading, or replace the caliper.

What does a caliper add compared with a plastic ruler?

A ruler reads only to its smallest printed division, usually a millimetre. The caliper holds the object between parallel jaws, its vernier scale gives a fraction of a main-scale division, and it can also measure inside diameters and depths.

Last Updated: September 2026