MTT-100

Vernier Calipers

The Vernier caliper consists basically of a stationary bar and a movable Vernier slide assembly.

The stationary rule is a hardened graduated bar with a fixed measuring jaw. The movable Vernier slide assembly combines a movable jaw, Vernier plate, clamp screws and adjusting nut.

The Vernier slide assembly moves as a unit along the graduations of the bar to bring both jaws in contact with the work. Readings are taken in thousandths of an inch by reading the position of the Vernier plate in relation to the graduations on the stationary bar.

The modern Vernier gages feature an improved long Vernier with 50 divisions instead of the older style with 25 divisions. However there are still Vernier gages with 25 divisions used in manufacturing and it is important that the user is able to read the 50 and the 25 division gages. The 50 division Vernier plate, with widely spaced, easy-to-read graduations and in combination with half as many bar graduations as previous old style instruments, make possible faster, more accurate and greatly simplified readings without a magnifying glass.

The Vernier principle is applied to many tools such as Vernier Height Gages, Vernier Depth Gages, Vernier Protractors, Gear Tooth Vernier Calipers, etc.

How to Read Vernier (English)

The bar is graduated into twentieths of an inch (.050"). Every second division represents
a tenth of an inch and is numbered. 

The Vernier plate is divided into fifty parts and numbered 0, 5,10,15, 20, 25, . . .45, 50.

The fifty divisions on the Vernier plate occupy the same space as forty-nine divisions on
the bar.

The difference between the width of one of the fifty spaces on the Vernier plate and one of the forty-nine spaces on the bar is therefore 1/1000 of an inch (1/50 of 1/20). If the tool is set so that the 0 line on the Vernier plate coincides with the 0 line on the bar, the line to the right of the 0 on the Vernier plate will differ from the line to the right of the 0 on the bar Pg. 28-29 by 1/1000; the second line by 2/1000 and so on. The difference will continue to increase 1/1000 of an inch for each division until the 50 on the Vernier coincides with the line 49 on the steel rule.

To read the tool, note how many inches, tenths (or .100) and twentieths (or .050) the 0 mark on the slide Vernier is from the 0 mark on the bar.

Then note the number of divisions on the slide Vernier from the 0 to a line which EXACTLY COINCIDES with a line on the bar.

EXAMPLE: In the above illustration the Vernier plate has been moved to the right one and four tenths and one twentieth inches (1.450), as shown on the bar and the fourteenth line on the slide Vernier EXACTLY COINCIDES with a line, as indicated on the illustration above. Fourteen thousandths of an inch are, therefore, to be added to the reading on the bar and the total reading is one and four hundred and sixty-four thousandths inches (1.464).

YOU ADD TO GET YOUR MEASUREMENT
A. 1.000 on the bar
B.   .450 also on the bar
C.   .014 on the Vernier plate (outside)
    1.464 is your measurement

HOW TO READ VERNIER CALIPERS (METRIC)

Each graduation on the bar is 1.00 mm. Every tenth graduation is numbered in sequence - 10 mm, 20 mm, 30 mm, 40 mm, etc. - over the full range ot the bar. This provides for direct reading in millimeters.

The Vernier plate is graduated in 50 parts, each representing 0.02 mm. Every fifth line is numbered in sequence - 0.10 mm, 0.20 mm, 0.30 mm, 0.40 mm, 0.50 mm - providing for direct reading in hundredths of a millimeter.

To read the gage, first count how many mm's lie between the 0 line on the bar and the 0
line on the Vernier plate. Then find the graduation on the Vernier plate that exactly coincides with a line on the bar and note its value in hundredths of a millimeter.

Add the Vernier plate reading in hundredths of a mm to the number of mm you counted on the bar. This is your total measurement.

YOU ADD TO GET YOUR MEASUREMENT
A. 27.00 mm on the bar
B. .42 mm on the Vernier plate
27.42 mm is your measurement

VERNIER GAGE, INSIDE AND OUTSIDE MEASUREMENTS

If you are using a (English) Vernier Gage, the same procedure is used for obtaining inside measurements as for outside measurements, however the top row of measurements are to be used.

The above also applies if you are using a (Metric) Vernier Gage. The top row of measurements is for inside work and the bottom row is for outside work.

Some Vernier Gage combines both English and Metric graduations on one gage. The top row on the bar and Vernier plate have Metric graduations. The bottom row on the bar and Vernier plate have English graduations. Both these scales can be used for direct reading for outside dimensions only.

For inside measurements it is necessary to add the width of the closed contacts to your dimension to arrive at the correct and complete measurement. The minimum measurement some are .250"  at the tips others .300" and must calculated. 

FINE ADJUSTMENT

After bringing the measuring contacts to the work by sliding the movable jaw along the steel rule, tighten the fine adjustment clamp screw. Rotate the fine adjusting nut to bring the measuring contacts into final position against the work. Tighten the lock screw to clamp the sliding Vernier scale into position.