Vernier Caliper - Definition, Principle, Types, Reading, Least count, Diagram

Vernier Caliper

The vernier caliper is precision instrument which can measure upto 1 / 1000th of an inch in british system and 0.02 mm in metric system

Vernier scales are made to read 1 / 1000" in inches and 1/50 mm. in metric size.

Principle of Vernier caliper

Vernier Caliper works on the difference of main scale and vernier scale.
It involves dividing a line of known length into a certain number of equal parts and then comparing the length of these division with those made on a line of the same length but with a number of division which are one more than on the first line.

Vernier caliper diagram


If a fixed scale f 1" length is divided into 4 equal parts and sliding scale of 1" length is divided into 5 equal parts, then difference will be 1/4 - 1/5 = 1/20 or 0.05". Now if the sliding scale is moved in such a way that the first line of the sliding scale coincides with the first line on the first scale, the distance moved by the scale will be .05".

Vernier Caliper Least Count 

In Metric System - 0.02 mm

In British System - 0.001 inch

Vernier Caliper Formula [Vernier Caliper Reading]

One parts of main scale is - 1/2 mm
24 main scale division = 1/2 * 24 = 12 mm
25 vernier scale divison = 12 mm
1 vernier scale divison = 12/25 mm
So according to Principle Least count = Main scale - Vernier scale
Least count = 1/2 - 12/25 = 1/50 = 0.02 mm

Parts Of Vernier Caliper

1.Outside Large Jaws -
                                      It is used to measure the outer side of any project.
2.Inside Small Jaws -
                                    It is used to measure the inside of any object.
3.Depth Rod -
                        It is Used to measure the depth of any project or hole
4.Main Scale - 
                         It is made from stainless steel
5. Vernier Scale (Metric) -
                                            it shows the measurement in 0.1 mm.

6. Movable Jaw

7. Fixed Jaw
8. Lock Screw

9. Sliding Unit

10. Beam


How to Read the Vernier caliper (British System)

(1) Note the number of full inches that show from the zero on the main scale to zero on the vernier. In Fig. 15.30, it will be 3.000".
(2) Read the number of division beyond the inch division which we have already taken (3) and note them. In the fig. it will be 5 which will read 0.5".

(3) Note the 1/40th division on the main scale. In fig. it will be 2 which will read 2/40 or 0.05".
(4) To read the vernier scale, note along the scale until you find the line on vernier coinciding with the main scale line. this may be nicely read with magnifying glass. in fig. we see that line 15 on the vernier scale is coinciding with the line on the main scale, which will read 0.015" because one line on the vernier scale reads 0.001".
(5) To get the total reading we add all the readings :- 3.000+0.500+0.050+0.015= 3.565".
The same way the reading on the metric vernier can be had.

Types of Vernier Caliper

1. Flat Edge Vernier Caliper

2. Knife Edge Vernier Caliper 

3. Flat and Knife Edge Vernier Caliper

4. Vernier Caliper Depth Gauge

5. Gear Tooth Caliper

6. Dial Caliper

Read for milling machine-

Read for Lathe machine operations -

How to make cnc/ vmc programme -

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