Gauges are inspection tools used to check the dimensions of manufactured parts without providing an actual measurement. There are various types of gauges classified by purpose, design, and what type of surface they check. Standard gauges match the nominal size while limit gauges check if a part is within the minimum and maximum limits. Other types include plug gauges for holes, snap gauges for shafts, and adjustable gauges. Gauges are also classified as working, inspection, or reference gauges based on their intended use. Proper gauge design and application is important to ensure accurate inspection of parts.

1. Gauges

2. GAUGES
• Gauges are inspection tools of rigid design,
without a scale, which serve to check the
dimensions of manufactured parts.
• Gauges do not indicate the actual value of the
inspected dimension on the work.
• They can only be used for determining as to
whether the inspected parts are made within
the specified limits.

3. Classification of Gauges
1.According to their type :
• (a) Standard gauges
• (b) Limit gauges.
2.According to their purposes :
• (a) Workshop.
• (b) Inspection.
• (c) Reference or master gauges.
3.According to the form of the tested
surface :
• (a) Plug gauges for checking holes.
• (b) Snap and Ring gauges for
checking shafts.
4.According to their design :
• (a) Single limit and double limit
gauges,
• (b) Single ended and double ended
gauges,
• (c) Fixed and adjustable gauges.

4. Standard Gauges
• Standard gauges are made to the Basic Size of the part to be tested and
have the measuring member equal in size to the mean permissible
dimension of the part to be checked. A standard gauge should mate with
some snugness.
Limit Gauges
• These are also called “Go” and “No Go” gauges. These are made to the limit
sizes of the work to be measured. One of the sides or ends of the gauge is
made to correspond to maximum and the other end to the minimum
permissible size.
• The function of limit gauges is to determine whether the actual dimensions
of the work are within or outside the specified limits. A limit gauge may be
either double end or progressive. A double end gauge has the “Go”
member at one end and “No Go” member at the other end. The “Go”
member must pass into or over an acceptable piece but the “No Go”
member should not.
• The progressive gauge has “No Go” members next to each other and is
applied to a workpiece with one movement. Some gauges are fixed for only
one set of limits and are said to be solid gauges. Others are adjustable for
various ranges.

5. WORKING GAUGES, INSPECTION GAUGES AND REFERENCE
GAUGES
• To promote consistency in manufacturing and inspection,
gauges may be classified as working, inspection, and reference
or master gauges :
Working Gauges
• Working gauges are those used at the bench or machine in
gauging the work as it being made.
Inspection Gauges
• These gauges are used by the inspection personnel to inspect
manufactured parts when finished.
Reference Gauges
• These are also called master gauges. These are used only for
checking the size or condition of other gauges and represent as
exactly as possible the physical dimensions of the product.

6. GAUGE DESIGN
• To a greater or lesser extent, every gauge is a
copy of the part which mates with the part for
which the gauge is designed.
• If a gauge is designed as an exact copy of the
opposed part in so far as the dimension to be
checked is concerned, it is called a 'Standard
Gauge'.
• In design of a gauge, simplicity should be the
main aim as simple gauges can take
measurements continuously and accurately.

7. Important Points for Design.
1. The form of 'Go' gauges should exactly coincide
with the form of the opposed (mating) parts.
2. 'Go' gauges are complex gauges which enable
several related dimensions to be checked
simultaneously.
3. In inspection, 'Go' gauges must always be put into
conditions of maximum impassability.
4. 'No Go' gauges are gauges for checking a single
element of feature.
5. In inspection, 'No Go' gauges must always be put
into conditions of maximum passability.

9. Taylor's Principle.
(for the design of gauges)
It states,
1. That a “GO” gauge shall check all the
dimensions at a time in what is called the
“Maximum material condition”.
2. That a “NOTGO” gauge shall check only one
dimension at a time in what is called the
“Minimum material condition”.

10. Gauge maker's Tolerance
• Keeping all above main points for gauge design in
view there are three methods of giving tolerances
on gauges (snap and plug gauges).
Wear Allowance Consideration on Gauge Maker's
Tolerance.
• Gauge Maker’s tolerance = 1/10 x Work tolerance
• Wear Allowance = 1/10 x GMT = 1/100 x Work
tolerance

11. Note: Also provide
wear allowance if
asked to do so,
regardless of the
work tolerance.

13. Note: Also provide
wear allowance if
asked to do so,
regardless of the
work tolerance.

14. Calculate the dimensions of plug and ring gauges to control the
production of 50 mm shaft and hole pair of H7d8 as per I.S.
specification. The fundamental deviation for ‘D' hole is given by
the equation 16D0.44. In addition, determine the type of fit.
Solve

17. Design Plug and Ring Gauge for following
Hole shaft combination 25 D6g7
The fundamental
deviation for g shaft =
-2.5D0.34
Solve

20. Plain Plug Gauges.
1. Nominal size.
2. Class of tolerance.
3. The word 'Go' on the 'Go' side.
4. The words 'No Go' on the 'No Go' side.
5. The actual values of tolerance.
6. Manufacturer's name or trade mark.

21. Plain Plug Gauges
• Generally the gauging members of the plain
plug gauges are made of suitable wear-
resisting steel and the handles can be made of
any suitable steel e.g. handles may be made of
light metal alloys for heavy plain plug gauges,
or suitable non-metallic handles may be
provided for smaller plain plug gauges. The
gauging surface of plain plug gauges are
normally hardened to not less than 750 H.V.
and suitably stabilised and ground and lapped.

25. Plain Ring Gauges

27. Double Ended Snap Gauges

29. Snap Gauges
Rib type snap gauges

30. Adjustable Snap Gauge

31. Plate snap gauges

32. Plate Snap Gauge

34. Snap Gauge with Heat Insulation

35. Combined Limit Gauge.
Tee-Bo type gauge

36. Taper Ring Gauge Taper Plug Gauge

37. Gauges for Tapers

38. The procedures described so far have been based on the assumption that the hole or shaft
under consideration is a straight diameter with no contour. There are, however, instances
when a hole must either have internal contour , or a shaft external contour, such as threads or
tapers. First, let’s consider the taper of holes or shafts.
Obviously, the type of go/no-go gauge used for a straight hole or shaft could not be used to
check a taper. The taper plug gauge is therefore a single-ended instrument rather than a
double-ended instrument. The shaft of the taper plug gauge is ground and polished to a very
high accurate representation of a tapered shaft, with the diameter, taper & concentricity of
the large and small diameters of the taper all made exactly.
TAPER PLUG AND RING GAUGES
To accommodate the diametrical measurement, the gauge is etched with two lines (or
provided with two ground steps) at the large end of the taper.
When the instrument (plug gauge) is inserted in to the tapered hole, the large diameter line
should remain outside of the hole and the small diameter line should be within the hole.

39. Next to check for correct taper, the operator must gently try to wiggle the instrument in the
hole. If the instrument can move from side to side in any direction, the taper is incorrect.
Movement at the large end of the taper means the taper is too steep. Movement at the small
end of the taper means the taper is too shallow.
This procedure will not tell the operator if the taper is mis-shaped between the large and small
ends of the taper. To accomplish this, the gauge is coated with a light coat of bluing and given
a slight twist on the mating surface. When the instrument is extracted, it is checked for marks
in the bluing. If the rub marks are even and evenly distributed, the taper is properly shaped.
Conversely, if the bluing has rubbed off unevenly or sporadically, the taper is mis-shaped.
The taper ring gauge works in very much same, albeit, opposite manner as the taper plug
gauge. The exception to this rule is that the bluing application for checking the shape of the
taper will go on the part instead of the gauge. In other words bluing for checking the shape of
a taper with a gauge will always go on the shaft, regardless of whether this is the gauge or the
part.

41. Example for checking taper:
CNC TOOL HOLDER SHANK

42. SLIP GAUGES
• Slip gauges often called Johannsen gauges are
rectangular blocks of steel having a cross-
section of about 30 by 10 mm.

43. • After being hardened, blocks are carefully finished on the
measuring faces to such a fine degree of finish, flatness and
accuracy that any two such faces when perfectly clean may be
“wrung” together.
• This is accomplished by pressing the faces into contact (keeping
them perpendicular) and then imparting a small twisting motion
whilst maintaining the pressure. The contact pressure is just
sufficient in order to hold the slip gauges in contact and no
additional intentional pressure.
• It is found that phenomenon of wringing occurs due to
molecular adhesion between a liquid film (whose thickness may
be between 6 to 7 X 10-6mm) and the mating surfaces.
• When two gauges are wrung together and the overall dimension
of a pile made of two or more blocks so joined is exactly the sum
of the constituent gauges.

44. • It is on the property of wringing units together for
building up combinations that the success of system
depends, since by combining gauges selected from a
suitably arranged combination, almost any dimension
may be built-up.

45. Wringing and Enforced Adhesion
• The term 'wringing' refers to the conditions of intimate and
complete contact and of permanent adhesion between
measuring faces which is brought about by wringing
together the surfaces in question without application of
pressure, assuming that the surfaces have been thoroughly
cleaned and exhibit a good standard of flatness and
smoothness. The wrung gauge can be handled as a unit,
without the need for clamping all the pieces together.
• It is believed that the phenomenon of wringing is due to
molecular adhesion between a liquid film and the mating
surfaces of the flat surfaces. In fact, the success of precision
measurement by slip gauges depends on the phenomenon
of wringing.

46. Wringing
Demo

47. • It has been found that the gap between two wrung flat pieces is of
the order of 0.00635 microns from which it would be very clear that
the film thickness in two wrung flat pieces contributes no effect.
• It should be remembered that slip gauges are wrung together by
hand through a combined sliding and twisting motion.
Process of Wringing slip gauges

48. • If during wringing, there is slightest feeling of roughness the
process should be stopped and the surfaces examined for
contamination
• First the gauge is oscillated slightly with very light pressure
over other gauge so' as to detect presence of any foreign
particles between the surfaces.
• One gauge is then placed perpendicular to other using
standard gauging pressure and rotary motion is then applied
until the blocks are lined up.
• In this way air is expelled from between the gauge faces
causing the two blocks to adhere. This adherence is caused
partly by molecular attraction and partly by atmospheric
pressure

49. Enforced Adhesion
• The 'enforced adhesion' refers to the condition of contact over the
entire surface and of permanent adhesion, which, owing to the lack
of flatness or smoothness, can only be brought about by the
application of pressure.
• It may be noted that the use of any extraneous agent to promote
adhesion is not correct and it is sometimes specified that surfaces
which are to be wrung together should be absolutely dry. On the
other hand, a truly clean surface, though difficult to attain may not
wring satisfactorily.
• The usual practice is to use silicone or filtered kerosene as lubricant,
apply a thin coat of same and wipe it as thin as possible.
• The property of measuring faces of a gauge block of adhering, by
sliding or pressing the gauge against the measuring faces of other
gauge blocks or the reference faces of datum surfaces, without the
use of any extraneous means.
Wringing

50. M112 Slip Gauge Set
Memorize the above values

51. Protector Blocks
• These are two additional 2 or 2.5 mm blocks
with a letter P on measuring faces and are
provided with high-grade sets of gauge blocks.
These are accommodated at each end of a
combination so that all the wear occurs on
them. These are made from tungsten carbide
or other suitable material and take all the
wear due to rubbing on surface plates.

52. Selecting slip gauges for required
dimension.
• Let us say that the dimension to be arranged is 58.975 mm.
• Always start with the last decimal place e.g.. here it is 0.005 mm
and for this 1.005 mm slip gauge is selected.
• Now dimension left is 58.975-1.005 =57.970mm.
• Take second decimal place ; and for it select 1.47 mm slip gauge.
• Therefore. the remainder is 57.970 - 1.47 =56.500 mm.
• [Note : One could have selected 1.07 mm piece also. but that way
we would have been left with 56.900 and for it we need another
1.4 mm piece. Our aim should be to choose minimum number of
slip gauges for a given dimension.]
• Next for 56.500 mm, we choose 6.500 mm piece and finally 50.000
mm piece.
• Thus, we have 50.000+6.550+ 1.47+1.005 =58.975mm.
• All these four slip gauges are wrung properly to get required
dimension.

53. List the slip gauges to be wrung together to produce an
overall dimension of 92.357mm using two protection
slips of 2.5mm size.
Original dimension = 92.357
Less two protection slips of 2.5mm= 5.000
87.357
1mm + 3rd place= 1.007
86.350
1mm + 2nd place= 1.35
85.00
10mm = 10.00
75.000
2.50mm (protection)
2.50mm (protection)
1.007
1.350
10.000
75.000
Combination= 2 protector slips of 2.500mm + 1.007,1.350,10.000 and 75.000mm

54. List the slip gauges to be wrung together to produce an
overall dimension of 72.3685mm using two protection
slips of 2.5mm size.
Original dimension = 72.3685
Less two protection slips of 2.5mm= 5.000
66.368
1mm + 3rd place= 1.008
65.360
1mm + 2nd place= 1.36
64.00
14mm = 14.00
50.000
2.50mm (protection)
2.50mm (protection)
1.008
1.360
14.00
50.000
Combination= 2 protector slips of 2.500mm +1.0005+ 1.008,1.36,14.000 and 50mm
67.3685
1mm + 4rth place= 1.0005
1.0005

55. List the slip gauges to be wrung together to produce an
overall dimension of 70.9885mm
Original dimension = 70.9885
69.988
1mm + 3rd place= 1.008
68.980
1mm + 2nd place= 1.48
67.500
17.5mm = 17.50
50.000
1.008
1.48
17.50
50.000
Combination= 1.0005 + 1.008 + 1.48 + 17.50 + 50mm
70.9885
1mm + 4rth place= 1.0005
1.0005

56. List the slip gauges to be wrung together to produce an
overall dimension of 62.2345mm
Original dimension = 62.2345
61.234
1mm + 3rd place= 1.004
60.23
1mm + 2nd place= 1.23
59.00
17.5mm = 9.00
50.000
1.004
1.23
9.00
50.000
Combination= 1.0005 + 1.004 + 1.23 + 9 + 50mm
62.2345
1mm + 4rth place= 1.0005
1.0005

57. List the slip gauges to be wrung together to produce an
overall dimension of 52.7895mm using one protection
slip of 2mm size.
Original dimension = 52.7895
Less one protection slips of 2mm= 2.000
49.789
1mm + 3rd place= 1.009
48.78
1mm + 2nd place= 1.28
47.5
22.5mm = 22.5
25.00
2mm (protection)
1.009
1.28
22.5
25.000
Combination= 1 protector slips of 2mm +1.0005+ 1.009+ 1.28+ 22.5 +25mm
50.7895
1mm + 4rth place= 1.0005
1.0005

58. List the slip gauges to be wrung together to produce an
overall dimension of 79.247mm using one protection slip
of 2mm size.
Original dimension = 79.247
Less one protection slips of 2mm= 2.000
77.247
1mm + 3rd place= 1.007
76.24
1mm + 2nd place= 1.24
75mm = 75.00
2mm (protection)
1.007
1.24
75.000
Combination= 1 protector slips of 2mm + 1.007+ 1.24+ 75mm

59. List the slip gauges to be wrung together to produce an
overall dimension of 64.3485mm
Original dimension = 64.3485
63.348
1mm + 3rd place= 1.008
62.34
1mm + 2nd place= 1.34
61.00
11mm = 11.00
50.000
1.008
1.34
11.00
50.000
Combination= 1.0005 + 1.008 + 1.34 + 11 + 50mm
64.3485
1mm + 4rth place= 1.0005
1.0005