Should vernier calipers be read?

Vernier calipers do not need to be evaluated.

Vernier caliper is a measuring tool for measuring length, inside and outside diameter and depth. The vernier caliper consists of a main ruler and a sliding vernier attached to the main ruler. The main ruler is usually in millimeters, while the cursor has 10, 20 or 50 scales. Vernier calipers do not read like other scales, and they are not designed for this function.

Take 10 scale caliper as an example, the 10 grid on the cursor is only equivalent to 9 grids on the main scale. Therefore, when a scale on the cursor is aligned with a scale on the main ruler, it means that the distance between the first scale on the cursor (that is, the zero scale) and the adjacent previous scale on the main ruler is the reading of the cursor alignment scale multiplied by 0. 1 mm, and it is easy to draw the reading rule of the vernier caliper as follows.

How to use vernier caliper

Wipe the measuring claw with a soft cloth to make it close, and check whether the zero scale line of the cursor is aligned with the main ruler. If they are aligned, they can be measured. If there is no alignment, zero error shall be recorded. The zero scale line of the cursor on the right side of the zero scale line of the ruler body is called positive zero error, and the zero scale line on the left side of the ruler body is called negative zero error (this regulation method is consistent with the regulation of the number axis, and the origin is positive to the right and negative to the left).

When measuring, hold the ruler with the right hand, move the cursor with the thumb, and hold the object with the outer diameter (or inner diameter) to be measured with the left hand, so that the object to be measured is located between the outer measuring claws, and when it is close to the measuring claws, it can be read.

When measuring the external dimensions of a part, the line between the two measuring surfaces of the caliper should be perpendicular to the measured surface and cannot be skewed. When measuring, you can gently shake the caliper and put it in a vertical position. Otherwise, the measurement result A will be larger than the actual size B; First, open the movable measuring claw of the caliper, so that the measuring claw can be clamped into the workpiece freely, then stick the parts on the fixed measuring claw, and then move the ruler frame, so that the movable measuring claw can contact the parts slightly and forcefully.

If the caliper is equipped with a micro-motion device, tighten the fixing screw on the micro-motion device at this time, and then turn the adjusting nut to make the measuring claw contact the part to read the dimension. Never adjust the two measuring claws of the caliper to be close to or even smaller than the measured size, and forcibly clamp the caliper to the parts. Doing so will deform the measuring claw, or make the measuring surface wear prematurely, so that the caliper will lose its due accuracy.