Calipers - outside caliper, inside caliper, jenny caliper - combination set - feeler gauge - pitch screw gauge
Calipers
Caliper is a tool used to transfer measurements from a part to a scale,
or other instrument. The measurement is then taken by rule between
the caliper joints. Calipers are very useful when dealing with hard to
reach locations that normal measuring instruments cannot reach. They
are an important measuring aid, and in the hands of a skilled worker,
they can be a real time-saver. The three common types of calipers are
the inside, the outside, and the hermaphrodite calipers. Calipers are
available with different features. Calipers consist of two legs that are
fixed firmly together at the top. Some calipers may have a fixed rivet
or screw, so that they will maintain the position in which they have
been set. Others have a spring loaded pivot point at the top and are
adjusted by a screw to open or close to the required position.
Types of calipers
Outside calipers
Outside calipers are used for measuring outside dimensions, for
example, the diameter of a piece of round stock.
Inside calipers
Inside calipers have outward curved legs for measuring inside
diameters, such as diameters of holes, the distance between two
surfaces, the width of slots, and other similar jobs.
Calipers: a. Firm joint calipers, b. Spring outside calipers,
c. Plain inside calipers, d. Spring inside calipers
Using outside and inside calipers
Calipers may be difficult to use. The accurate transfer of measurement
when using calipers depends upon the affectivity of the calipers
against the work. 'Feel' is the light pressure of the calipers as they
pass over the work. "Feel" skill is required for positioning hand
measurement tools and interpreting the measurement
result. Following steps/rules for using the calipers.
1. Do not force calipers, they will bend easily, and affect the
accuracy of the measurements made.
2. Make fine adjustments by either tapping one leg on a hard
surface to close the gap or by tapping the jointed end of the tool
to open the legs slightly. Practice fine adjustment of calipers with
one hand; this will leave you a free hand to steady the work.
3. For accuracy when setting any calipers to a rule, it is important
to read off the measurement at eye level.
4. If measurements are made using calipers for comparison, one
operator should make all of the measurements (this keeps the
feel factor a minimal error source).
5. Obtain `feel' of caliper on diameter to be measured. The
important thing to develop is a sensitive "feel" of the caliper and
workpiece. Hold one toe of the caliper in contact with work and
adjust the other leg until a slight “drag” can be felt on the other
toe as you rock it back and forth. This “feel” can only be
achieved by practice. The feel that is provided as the tool passes
over center is the limit of its sensitivity.
Obtaining the `feel' and Setting to the work
6. Setting an outside caliper i. Hold the steel rule so that it resets on the fingertips of one
hand.
ii. Hold the outside caliper in the other hand. It should be
possible to comfortably turn the adjusting screw with the
thumb and the first and middle fingers.
iii. Hook one leg over the end of the rule and adjust the other
leg to the required measurement as shown in the figure
below.
Setting outside calipers to a rule
iv. Adjust the second leg until it splits the division of the
required measurement on the steel rule.
v. Recheck the measurement by holding the one leg against
the end of the rule. The end point of the second leg should
be at the measured point.
7. To set inside calipers, rest both the toe of one leg and the end of
the rule on a flat surface and adjust the other leg as before.
Setting inside calipers to a rule
8. For transferring caliper measurement, place the toes of the tools
in contact, steadying them with a finger of one hand and adjust
to match.
Combination Set
The combination set, as its name implies, is a tool that has several
uses. The set consists of a blade (graduated rule), square head,
protractor head, and center head. The grooved rule is used with each
head. The groove permits the rule to be moved into position and
locked.
Combination set
Feeler gauge
A feeler gauge is a tool used to measure gap widths. Feeler gauges are mostly used in engineering to measure the clearance between two parts.
Feeler gauge set (25 pieces, 0.03~1.0 mm measurement range)
Thread pitch gauges
Thread pitch gauges are used as a reference tool in determining the pitch of a thread that is on a screw or in a tapped hole. This tool is not used as a precision measuring instrument, rather it allows the user to determine the profile of the given thread and quickly categorize the thread by shape and pitch. This device also saves time, in that it removes the need for the user to measure and calculate the pitch of the threaded item.
Three different sets of threading gauges. The uppermost gauge is an ISO metric pitch gauge, the larger gauge in the center is for measuring the Acme thread form, and the lower gauge is for Whitworth screws.
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