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• 25 .00 mm - Zero READING of 25-50 micrometer
• 4.00 mm - 4 main divisions (4 * 1 mm)
• 0.50 mm - 1 subdivision (1 * 0.5 mm)
• 0,21 mm - 21 thimble divisions (21* 0.01 mm)
• So the TOTAL reading is 29.71 mm

• 15 .00 MM - 15 MAIN scale divisions (15*1 mm)
• 0.50 mm - 1 subdivision (1* 0.5 mm)
• 0.30 mm - 15 vernier divisions (15* 0.02 mm)
• So the TOTAL reading is 15.80 mm

• 1 degree= 60 MINUTES 
• 1 MINUTE= 60 seconds
• 12 DIVISION on vernier scale = 23 degree 
• one division on vernier scale = 23/12 = 23*60/ 12= 115 minutes
• 1 vernier scale division is less than 2 degree
• so, value of 2 degree on dial = 2*60 = 120
• Value of one vernier scale division = 115
• Least count = 120-115= 5 minutes

• 10 vernier divisions = 9 THIMBLE divisions 
• 1 thimble division = 0.01 mm
• 10 vernier divisions =0.09 mm 
• and 1 vernier division =0.09/ 10 = 0.009 mm
• so the difference is the value of ONE thimble division – value of 1 vernier division = 0.01-0.009 mm = 0.001 mm

• Value of SINE 20 degree = 0.3420 (from sine table)
• Hypotenuse is the LENGTH of sine BAR i.e 100 MM.
• Height of slip GAUGES = Hypotenuse * sine 20 = 100* o,3420 mm =34.20 mm

• Plug gauge. It is USED for checking the diameter of the hole. It may be found in single ENDED, double end or PROGRESSIVE type.
• Snap gauge. It is used for checking the external DIMENSION of the parts. It may be found in solid, adjustable or double ended type.

• Temporary coating, like grease, oil or varnish etc.
• Semi-permanent coating, like painting, COLORING of brass, BLUING of steel, black FINISH of steel, tinning, galvanizing etc.
• Permanent coating, like chromium PLATING, nickel plating, SILVER plating etc.

Honing is an OPERATION of finishing CYLINDRICAL surfaces to a fine degree of accuracy by means of ABRASIVE STICKS.

Honing is an operation of finishing cylindrical surfaces to a fine degree of accuracy by means of abrasive sticks.

• To FINISH the job up to the LAST digit of accuracy.
• To get good SURFACE finish.
• To control the size.
• To get desired FIT.

Lapping is an operation of FINISHING the flat and the CYLINDRICAL surfaces to a FINE degree of accuracy by means of a LAP and lapping compound. It may be DONE by hand or by machine.

Lapping is an operation of finishing the flat and the cylindrical surfaces to a fine degree of accuracy by means of a lap and lapping compound. It may be done by hand or by machine.

• SELECTIVE Assembly - This assembly is slow and expensive, ALSO the maintenance is difficult to manage since the SPARES are not easily available. For example special threaded NUT and bolt in which each nut fits only one bolt.
• Non-Selective Assembly - It is quiet rapid and less expensive, maintenance is very easy since the spares are widely available. For example any nut fits on any bolt of same size and the type of thread.

• PRODUCTION of a unit, COMPONENT or part in large scale or number is called mass production.
• Time consumption of manufacturing.
• Reducing the manufacturing COST.
• Interchangeability of PRODUCTS.

• H8/g7 indicates sliding FIT or close running fit which INCLUDES the group of clearance fit.
• H7/p6 indicates light PRESS fit which includes the group of INTERFERENCE fit.

• Scope. This standard makes recommendations relating to limits of size of parts or components and to fits constituted by their ASSEMBLY.
• Symbols. Following symbols are used in this standard,
• Upper deviation of a hole ES (Ecart Superieur)
• Lower deviation of a hole EI (Ecart Inferieur)
• Upper deviation of a SHAFT es
• Lower deviation of a shaft ei
• Fits. When the parts are to be assembled, the relation resulting from the differences between the sizes before assembly is KNOWN as Fit. Depending up on the limits of the hole or shaft, the fit may be a clearance, a transition or an interference.
• Hole Basis System. In this standard, the different clearances and INTERFERENCES are obtained in associating various shafts with a single hole, whose upper deviation is zero and the symbol is H.
• Shaft Basis System. In this, the different interferences and clearances are obtained in associating various shafts with a single shaft, whose upper deviation is zero and the symbol is h.
• Indication of Fit. A fit is indicated by the basic size common to both components followed by symbols corresponding to each COMPONENT, the hole being quoted first.
• Eg : 40 H7/g 6 or 40 H 7 – g 6

• It saves time and labor charges.
• It gives more employment due to mass PRODUCTION.
• IMPROVES the efficiency of workers.
• Easy to assemble due to INTERNATIONAL trade mark.
• Minimize overall production cost.

Interchangeability is that the manufacturing of SIMILAR components under mass production can be ASSEMBLED and replaced without any further TREATMENT as well as without AFFECTING the functioning of the component.

Interchangeability is that the manufacturing of similar components under mass production can be assembled and replaced without any further treatment as well as without affecting the functioning of the component.

The Free and the Snug are the fits come under the CLEARANCE fit but Snug Fit has CLOSE CONTACT than that of Free Fit.

The Free and the Snug are the fits come under the clearance fit but Snug Fit has close contact than that of Free Fit.

• Clearance Fit - It is a KIND of fit which always provides clearance with positive allowances. The tolerance region of the HOLE is above than that of the shaft.
• TRANSITION Fit - This type of fit always has close providing by either a clearance or an interference. The tolerance region of the hole and shaft overlaps. 
• Interference Fit - It is a fit which always provides interference with negative allowances. The tolerance region of the hole is below the size than that of the shaft.

Hole basis system is more POPULAR, because it has MANY advantages over the Shaft basis system, such as,

• It is easier to vary the size of the shaft than that of hole
• More adaptable to PRODUCE hole of standard size than that of shaft, because of majority of hole in engineering WORKS is FINISHED to its nominal size by using drills and reamers of standard size.

Hole basis system is more popular, because it has many advantages over the Shaft basis system, such as,

• Shaft basis system - In this system, the size of shaft is and VARIOUS CLASSES of fits can be obtained by giving tolerance on hole
• Hole basis system - In this system, the size of hole is CONSTANT and various classes of fits can be obtained by giving tolerance on SHAFTS

• It saves the LABOUR charges.
• It saves the material from wastage. 
• It saves the TIME.
• PRODUCTION can be increased .
• It helps to REDUCE the manufacturing COST of the parts.

It is algebraic DIFFERENCE between an ACTUAL SIZE and corresponding basic size.

It is algebraic difference between an actual size and corresponding basic size.

Ii is the graphical representation of the basic SIZE. The DEVIATIONS are MEASURED from this LINE.

Ii is the graphical representation of the basic size. The deviations are measured from this line.

It is the DEVIATION which is conveniently chosen to define the position of the TOLERANCE zone in RELATION to zero LINE.

It is the deviation which is conveniently chosen to define the position of the tolerance zone in relation to zero line.

This is the graphical representation of the REGION between UPPER and LOWER LIMIT.

This is the graphical representation of the region between upper and lower limit.

• Unilateral Tolerance : If the variation from BASIC size is in ONE direction, SYSTEM of tolerance is CALLED unilateral.
• Bilateral Tolerance : If the variation from basis size is in both direction, system of tolerance called Bilateral Tolerance.

• Easiest method of marking identical PARTS.
• If the design of template is not suitable, it can be REPAIRED or REPLACED easily.
• It REDUCES the production COST.

• To make identical parts.
• To check the SHAPE of MANUFACTURED parts.

A SINE bar is specified by the DISTANCE between the center of two rollers. Sine bars are generally available in 100 mm to 250 mm SIZES.

A sine bar is specified by the distance between the center of two rollers. Sine bars are generally available in 100 mm to 250 mm sizes.

• A sine bar consists of an ACCURATELY finished steel bar having two rollers of equal diameter which are placed at the fixed distance. It is used for setting and measuring angles together with slip gauges, surface plate and dial test INDICATOR.
• The name Sine bar, because it works as a HYPOTENUSE in a right angle triangle.

• The slip gauges must be kept SEPARATED, cleaned, and DUST free when not in use.
• Do not keep the slip gauges in a magnetic field, keep out from temperature fluctuations and should not be exposed in dampness.
• Avoid the contact between the slip gauges for a long TIME.
• Functional surfaces must be secured from SCRATCHES and hand or finger contacts.
• Use only LINEN cloth or chamois leather for cleaning purpose.

The method of twisting the GAUGE BLOCKS while setting it to required HEIGHT is known as Wringing of SLIPS.

The method of twisting the gauge blocks while setting it to required height is known as Wringing of slips.

• To check the accuracy of precision instruments.
• GAUGE blocks are also used along with sine BAR for setting DIMENSIONS to the required heights to read the ANGLE.

These gauges are USED to check the hole DIMENSIONS in limit. The HIGH limit end of this gauge should not GO in to the hole which is called NOT GO and the LOW limit end should go in to the hole which is called GO end.

These gauges are used to check the hole dimensions in limit. The high limit end of this gauge should not go in to the hole which is called NOT GO and the low limit end should go in to the hole which is called GO end.

A FEELER gauge is used to MEASURE the GAP between two MATING parts.

A feeler gauge is used to measure the gap between two mating parts.

• Work SHOP Gauges are generally used in workshops to inspect the job WITHIN an accuracy of 0.025 MM. Semi skilled WORKERS are the beneficiaries.
• Inspection Gauges COMMONLY used to check up more accurate components and also inspect the workshop gauges within an accuracy of 0.0025 mm.

• It INCREASES the PRODUCTION.
• It saves the time.
• It MAKES the parts interchangeable.
• It REDUCES the supervision charges.
• It minimizes the production cost.

A Gauge is a checking instrument which is COMMONLY USED in tool room and machine SHOP for checking the FINISHED COMPONENTS.

A Gauge is a checking instrument which is commonly used in tool room and machine shop for checking the finished components.

It is a circular piece of GLASS or fused quartz with its TWO plane faces FLAT and parallel and the surfaces are finished to an optical degree of flatness, Optical flat ray in size between 25 and 300 MM diameter. Quartz flats have high of wearing quality than the optical glasses and have minimum expansion of heat. When an optical flat is placed over a flat surface being measured, a series of rainbow bands are observed which are known as interference bands. Better results can be obtained under colored LIGHT because bands are more clearly visible. The optical flats are used for testing the flat surfaces of engineering instruments.

It is a circular piece of glass or fused quartz with its two plane faces flat and parallel and the surfaces are finished to an optical degree of flatness, Optical flat ray in size between 25 and 300 mm diameter. Quartz flats have high of wearing quality than the optical glasses and have minimum expansion of heat. When an optical flat is placed over a flat surface being measured, a series of rainbow bands are observed which are known as interference bands. Better results can be obtained under colored light because bands are more clearly visible. The optical flats are used for testing the flat surfaces of engineering instruments.

• The COMPONENTS can be checked quickly during mass PRODUCTION.
• For the INSPECTION of newly PROCURED gauges.
• In selective assembly of parts where parts are graded in groups depending up on their tolerances.
• As laboratory standard where working and inspection gauges set and correlated.
• Attached with some MACHINES which can be used as working gauge to prevent work spoilage and to maintain required tolerances at all stages of manufacturing.

• To check the parallelism of MACHINED or GROUND SURFACES.
• To check the true rotation of round jobs.
• To compare the dimensions of finished COMPONENTS.

Gear tooth Vernier CALIPER id made with vertical and horizontal scales. So MOVEMENT can be taken at a time with these two scales. It is used to measure the chordal ADDENDUM and chordal thickness of a gear tooth WITHIN the accuracy of 0.02 MM or 0.001”.

Gear tooth Vernier caliper id made with vertical and horizontal scales. So movement can be taken at a time with these two scales. It is used to measure the chordal addendum and chordal thickness of a gear tooth within the accuracy of 0.02 mm or 0.001”.

• Minimum READING is 5 minutes.
• Main scale and VERNIER scale are on the same plane to eliminate the reading parallax.
• Fine adjustment of the BLADE insures the precision measuring and laying out of ANGLE.
• Main PARTS are of hardened stainless steel to prevent rust.
• Combined with an attachment or Height gauge, a wide range of measurements is available.

BACKLASH is the lack of MOTION or lost motion of the spindle when the rotation of the THIMBLE is changed the DIRECTION.

Backlash is the lack of motion or lost motion of the spindle when the rotation of the thimble is changed the direction.

Zero READING of a micrometer is the INITIAL reading which may vary according to the size of the micrometer.

• Zero reading of 0-25 MM micrometer is 0
• Zero reading of 25-30 mm micrometer is 25 mm
• Zero reading of 50-75 mm micrometer is 50 mm etc

Zero reading of a micrometer is the initial reading which may vary according to the size of the micrometer.

• There is zero error in MICROMETER.
• Dirty WORK piece or measuring faces of micrometer.
• Unengaged Ratchet stop.
• Taking measurement when the job on motion.
• Wrong way of holding Micrometer.
• TEMPERATURE variation between the work piece and the MICRO meter.

Ratchet stop supports to MEASURE accurate reading applying uniform pressure on the MEASURING faces irrespective of OPERATOR’s skill and STRENGTH.

Ratchet stop supports to measure accurate reading applying uniform pressure on the measuring faces irrespective of operator’s skill and strength.

A vernier depth GAUGE is used to measure and CHECK the depth of blind holes, STEPS etc. to the ACCURACY of 0.02 mm 0.001”.

A vernier depth gauge is used to measure and check the depth of blind holes, steps etc. to the accuracy of 0.02 mm 0.001”.

Vernier BEVEL PROTRACTOR is USED to measure and check the angles of a job to the ACCURACY of 5’ (5 MINUTES).

Vernier Bevel Protractor is used to measure and check the angles of a job to the accuracy of 5’ (5 minutes).

• For MAKING PARALLEL lines on the work PIECE to the accuracy of 0.02 MM in metric system and 0.001” in inch system.
• For COMPARING heights of finished work piece.