3. GAUGES
โข Gauges perform an essential services in any
scheme of quantity production on an
interchangeable basis
โข A gauge (or Limit Gauge) is a tool or instrument
to measure or compare a component.
โข It is employed in the sense of an instrument
which having fixed dimension, is used to
determine whether the size of some
component exceeds or is less than the size of
the gauge itself
4. ๏ก Gauges are used for dimensional control of
the component parts , their function being to
establish whether or not surface levels lie
within the zone specified by the designer.
๏ก Gauges must be manufactured & checked
with reference to standard of length, which in
turn is related to a fundamental length
standard. The standard of length is then
transferred through the gauge to the
component
5. ๏ก The true value of a gauge is measured by its
accuracy & service life which, in turn,
depends on the workmanship & materials
used in its manufacture. Since all gauges are
continually subject to abrasive wear while in
use, the selection of the proper material is of
great importance
๏ก High carbon steel & alloy tool steels have
been the principal materials for manufacture
of such gauges
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10. Classification
โข According to design
โ single limit and double limit gauges
โ single ended and double ended gauges
โ fixed and adjustable gauges
11.
12. Standard gauge
โข If a gauge is made as an exact copy of the
mating part of the component to be checked
ex: bush for shaft
13. Limit gauge
โข Used widely in industries
โข For two permissible limits of the dimension of
a part
โข Two gauges are required for two limits
โข These are GO and NO GO gauges
โข GO gauge foe MML
โข NO GO for LML
14. Limit Gauge
โข Limit gauges are made to the limits of the dimensions of
the part to be tested. There are two limit of dimensions,
so we need two limit gauge.
โข โGo gaugeโ should pass through or over a part while โNot
Go gauge 'should not pass through or over the part.
18. Types of limit plug gauges
1. Solid type
2. Renewable type โ taper inserted type
3. Fastened type โ single, double ended
4. Flat type
5. Progressive type
6. Pilot plug gauge
7. Combined dual purpose type
41. TAPER GAUGE
โข The most satisfactory method of testing a
taper is to use taper gauges.
โข They are also used to gauge the diameter of
the taper at some point.
โข Taper gauges are made in both the plug and
ring styles and, in general, follow the same
standard construction as plug and ring gauges.
45. THREAD GAUGE
โข Thread gauges are used to check the pitch
diameter of the thread.
โข For checking internal threads (nut, bushes, etc.),
plug thread gauges are used, while for checking
external threads (screws, bolts, etc.), ring thread
gauges are used.
โข Single-piece thread gauges serve for measuring
small diameters.
โข For large diameters the gauges are made with
removable plugs machined with a tang.
48. FORM GAUGE
โข Form gauges may be used to check the
contour of a profile of work piece for
conformance to certain shape or form
specifications.
Template Gauge
โข It is made from sheet steel. It is also called
profile gauge. A profile gauge may contain two
outlines that represent the limits within which
a profile must lie
49.
50. SCREW PITCH GAUGE
โข Screw pitch gauges are used in picking out a
required screw and for checking the pitch of the
screw threads.
โข They consist of a number of flat blades which are
cut out to a given pitch and pivoted in a holder.
โข Each blade is stamped with the pitch or number
of thread per inch and the holder bears an
identifying number designing the thread it is
intended for.
51.
52. RADIUS AND FILLET GAUGE
โข The function of these gauges is to check the
radius of curvature of convex and concave
surfaces over a range from 1 to 25 mm.
โข The gauges are made in sets of thin plates
curved to different radius at the ends.
โข Each set consists of 16 convex and 16 concave
blades.
54. FEELER GAUGE
โข Feeler gauges are used for checking clearances
between mating surfaces.
โข They are made in form of a set of steel, precision
machined blade 0.03 to 1.0 mm thick and 100
mm long.
โข Each blade has an indication of its thickness.
โข To find the size of the clearance, one or two
blades are inserted and tried for a fit between the
contacting surfaces until blades of suitable
thickness are found.
56. INDICATING GAUGES
โข Indicating gauges employ a means to magnify
how much a dimension deviates, plus or minus,
from a given standard to which the gauge has
been set.
โข They are intended for measuring errors in
geometrical form and size, and for testing
surfaces for their true position with respect to
one another.
โข Indicating gauges can be of a dial or lever type.
57. Materials which are used for making gauges are high carbon and
alloy steels, cemented carbides, etc.
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59. 59
Taylorโs Principle
โข Go Gauge should always be so designed that
it will cover the Maximum Metal
Condition(MMC) of as many dimensions as
possible in the same limit gauge,
whereas Not Go gauge to cover the minimum
metal condition of one dimension only.
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Design of Limit Gauge
โข Allocation of Tolerance
โ Manufacturing Tolerance
โ Wear Allowance
โข Taylorโs Principle of gauge Design
โข Fixing of Gauge elements with handles
โ Taper lock design
โ Trilock Design
โข Provision of Guards
โข Provision of Pilot Correct Centering
โข Materials
โข Hardness and Surface finish
โข Rigidity
โข Alignment of Gauge faces
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Allocation of Tolerance
Manufacturing Tolerance
โข It is economically impractical to attempt to make โGoโ and โNot Goโ
gauges exactly to the two limits of work tolerance.
โข Limit gauges are made 10 times more accurate than the tolerances
they are going to control.
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Allocation of Tolerance
Wear Allowance
โข The surface of โGoโ gauge is constantly rub
against the surface of the part in inspection and loose
their initial size.
โข The size of plug gauge is reduced but size of snap
gauge is increased.
โข 10% wear allowance is provided only for the โGOโ
gauge if working tolerance is greater than 0.09 mm.
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KEY WORDS
Standard Gauges : These are made to the nominal size of the parts to
be tested.
Limit Gauges : These are โgoโ and โno goโ gauges.
Plug Gauges : These are used for checking holes of many different
shapes and sizes.
Ring Gauges : External diameter measuring gauges.
Taper Gauges : Taper testing gauges.
Snap Gauges : These are used for checking shafts.
Thread Gauges : These are used for pitch diameter of the thread.
Form Gauges : These are used to check the contour of a profile.
Feller Gauges : For checking the clearance between the mating
surfaces.
Indicating Gauges : To measure the position of the surfaces.