HackSpace – September 2019

(Wang) #1
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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