HackSpace – September 2019

FORGE

The results appear on the LCD. Most calliper sets
have imperial and metric selections. Some also
include a fractional measurements mode.

Inside Diameter The smaller ‘faces’ at the top of the

callipers are for measuring the inside diameter of an

object. The jaws here are inverted from the main

ones, but work in the same fashion. You open them

to the walls of whatever inside area you are

measuring and find the reading on the LCD.

Depth On the back end of callipers’ ruler/scale is

found a depth gauge (or ‘depth bar’). This is used to

measure, for instance, the depth of a hole. Simply

extend the bar into the distance to be measured, and

read the results on the display.

Step You can measure the difference between two

surfaces using the outside measuring face (main

jaws). You simply place the outside edge of the sliding

jaws against one of the edges you are measuring and

the outside edge of the inner, fixed jaw against the

other edge. The display will reveal this distance.

Some models of callipers have a fine adjustment

screw that allows you to move the jaws more

precisely. Some also have a set screw so that you can

tighten to hold a measurement. Knowing how much

pressure to apply when taking a measurement takes

some practice. It’s often a good idea to take several

measurements along an object and average them out

to get closer to a reliable number.

Other uses and measuring tricks:

Using callipers like a funky slide rule You can use

callipers as a conversion calculator. Simply move the

fine adjustment wheel (if you have one) on your

callipers to the number along the scale that you wish

to convert, then press the Mode button to switch

between millimetres, inches, and fractions (if your set

has this mode). Digital slide-rule!

Measuring the balance thickness of a ‘blind hole’

Let’s say you have a blind hole (a hole that does not

go all of the way through) in a workpiece, and you

want to know the difference between the depth of

that hole and bottom edge of your piece. Simply use

the depth bar to measure the depth of the hole, zero

out your callipers, and then measure the overall

height of the piece. The result shown will be the

balance of the blind hole.

Measuring centre-to-centre distance When

measuring the centre-to-centre distance between two

holes, first measure the hole diameter. Then zero out

your callipers and measure from near-edge to

near-edge of your two holes. (The hole diameter,

which you zeroed out, will be automatically

subtracted). This gives you your centre-to-centre

distance. This is particularly useful when trying to

figure out where to place PCB mounting posts when

designing project enclosures.

Callipers are also known as a vernier, which is a

short scale made to slide along a graduated

instrument for indicating divisions.

Thanks to

Lenore Edman, Jeff Worley, Richard Gould, Jake Hildebrandt

Figure 1

The top faces

are used for

inside diameter

measurements

Figure 2

The bottom ‘jaws’,

known as ‘faces’,

are used to measure

outside diameters

Figure 3

You can use the

distance between the

edge of the inside

face and the outer

edge of the outside

face to measure the

distance between

two edges

Figure 4

The ‘depth bar’ found

on the opposite end

from the faces is

used to take

depth measurements

YOU’LL NEED

A set of digital

callipers

Something

to measure

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