metrology sine bar
TRANSCRIPT
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Welcome to Session on metrology
E.GowdhamanBE(Mech),MBA(IT&HR)
Sr.Engineer
MSME Tool Room ,Bhubaneswar
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Session Two
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• Angle measurement principle• Sine Bar• Sine Vice• Slip gauge
Out Line
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Principle• Principle of the sine bar is based on trigonometrical
function• Sine bar used to measure angles using with the help of
gauge blocks and a dial gauge or a spirit level. • The aim of a measurement is to make the surface on
which the dial gauge or spirit level is placed horizontal.
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04/11/2023 [email protected]
Trigonometrical function
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Example• To measure the angle of a wedge, the wedge is
placed on a horizontal table. • The sine bar is placed over the inclined surface
of the wedge. • At this position, the top surface of the sine bar
is inclined the same amount as the wedge. • Using gauge blocks, the top surface is made
horizontal. • The sine of the angle of inclination of the wedge
is the ratio of the height of the gauge blocks used and the distance between the centers of the cylinders.
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Features • This is the rectangular bar made up of
stabilized chromium steel • Surface accurately finished by grinding and
lapping• Two precision rollers of same diameter are
mounted on either end of the bar• The centre of line of the rollers is parallel to the
top of the face of the sine bar • The holes drilled across the bar are to reduce
the weight and used for climbing on angle plate
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Features • The length of the sine bar is the distance
between the center of the rollers.• Commonly available sizes are 100mm, 200mm,
250mm and 500mm• Size of the sine bar is specified by length
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Uses
• Where high degree of accuracy to less then one minute is needed
• Measuring angle• Marking out• Setting up for machining
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Construction• It consists of a hardened, precision ground body with
two precision ground cylinders fixed at the ends. The distance between the centers of the cylinders is precisely controlled, and the top of the bar is parallel to a line through the centers of the two rollers.
• The dimension between the two rollers is chosen to be a whole number (for ease of later calculations) and forms the hypotenuse of a triangle when in use. The image shows a 10 inch and a 100 mm sine bar.
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Measurement• When a sine bar is placed on a level surface the top edge will be
parallel to that surface. If one roller is raised by a known distance, usually using gauge blocks, then the top edge of the bar will be tilted by the same amount forming an angle that may be calculated by the application of the sine rule.
• The hypotenuse is a constant dimension — (100 mm or 10 inches in the examples shown).
• The height is obtained from the dimension between the bottom of one roller and the table's surface.
• The angle is calculated by using the sine rule. Some engineering and metalworking reference books contain tables showing the dimension required to obtain an angle from 0-90 degrees, incremented by 1 minute intervals.
• Angles may be measured or set with this tool.
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Slip Gauge
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What is Slip Gauge• Slip gauges are often called Johannsen gauges also, as
Johannsen originated them. • These are rectangular blocks of steel having a cross-
section of about 30 by 10 mm. • These are first hardened to resist wear and carefully
stabilised so that they are independent of any subsequent variation in size or shape.
• 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
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Grades of Slip Gauge.
• The slip gauges can be graded into three categories,
Grade 0, Grade I and Grade II. • High degree of finish and flatness of the slip gauges
makes it possible for a number of gauges to be wrung together to form a composite size,
• Accuracy of length of gauges, their flatness, parallelism and hardness.
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Use of Slip Gauge Grades• Grade 2. This is the workshop grade. Typical uses
include setting up machine tools, positioning milling cutters and checking mechanical widths.Grade 1. Used for more precise work, such as that carried out in A good-class tool room. Typical uses include setting up sine bars and sine tables, checking gap gauges and setting dial test indicatorsto zero.
• Grade 0. This is more commonly known as the Inspection grade, and its use is confined to tool room or machine shop inspection..
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Set of 45 & 85- M45 & M85
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Range Step(All dimensions in mm)Pieces
1.001 to 1.009 0.001 9
1.01 to 10.9 0.01 9
1.1 to 1.9 0.1 9
1 to 9 1 9
10 to 90 10 9
Total 45
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Slip Gauge Material
• Made from high grade steel with coefficient of thermal expansion (11.5 ± 1.5) x 10-6 per degree Celsius between 10°C and 30°C.
• Hardened throughout and suitably heat-treated.• Suitably stabilized their dimensions are
provided with hard measuring faces like carbide faces.
• The hardness of the slip gauges is alwaysmore than 800 HV (Vickers Hardness)
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Salient Features of slip gauge
• Corrosion Resistant— Unaffected by water, acids and alkalies.— Simple maintenance with no requirement of any anti-corrosion treatment.— No adverse effects due to fingering while using.
• Superior Wringability
— The uniform and close grain structure enables the blocks rigidly wrung together and easy tooperate. Dents and burrs are not easily produced on gauge surface.
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Salient Features of slip gauge• Resistant to Impact
—Blocks are hard and highly tough to withstand the knocks and dropsthat occur during use and will not chip or fracture easily.
• Resistant to Wear
—The natural stability and durability due to its low friction co-efficient maintains their geometry longer.
• Thermal Expansion
— Co-efficient of thermal expansion of ceramic is 10 x lO^fC is very close to that of steel.— The lowest thermal conductivity makes these gauge blocks easy to use at differenttemperatures.
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Construction of slip Gauge
• According to IS : 2984—1966, the size of a slip gauge is defined as the distance betweentwo plane measuring faces, one being constituted by the surface of an auxiliary body with which one of the slip gauge faces is wrung and the other by the exposed face to the slip gauge.
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Wringing Slip Gauge• Process of sliding two blocks together so that their
faces lightly bond. • Molecular attraction between the blocks, and forms a
very strong bond• May withstand a 200 lb (890 newton) pull. • Physics responsible for this phenomenon remains
unclear.• Possible causes that have been suggested are:
atmospheric pressure, molecular attraction, a minute film of oil, or a combination of these factors
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Determining slip Gauge
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Determining slip Gauge
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Calculation
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