Linear measurements vernier and micro meter

Linear measurements vernier and micro meter

1. VERNIER CALIPER:- The simplest method is to read the position of the pointer directly on the scale. When the pointer is between two markings, the user can mentally interpolate to improve the precision of the reading. This would be a simple calibrated caliper; but the addition of a vernier scale allows more accurate interpolation, and is the universal practice; this is the vernier caliper. Outside large jaws: used to measure external diameter or width of an object Inside small jaws: used to measure internal diameter of an object Depth probe/rod: used to measure depths of an object or a hole Main scale (Metric): scale marked every mm Main scale (Imperial): scale marked in inches and fractions Vernier scale (Metric) gives interpolated measurements to 0.1 mm or better Vernier scale (Imperial) gives interpolated measurements in fractions of an inch Retainer: used to block movable part to allow the easy transferring of a measurement

2. LEAST COUNT OF VERNIER

3. PROBLEMS ON VERNIER

4. MICROMETER A micrometer is a tool used for the precise measurement of very small objects. A micrometer can measure the depth, length and thickness of whatever object fits between its anvil and spindle. It is commonly used in mechanical engineering and machining applications. Working Principle In a micrometer screw gauge measurements are done actually through a precisely made integrated screw with a pitch of usually but not necessarily 02 threads per millimeter, which means that on completing exactly one revolution the displacement achieved is half of a mm i.e. 0.5 millimeter.

5. Least Count. The least count of screw gauge represents minimum value of a dimension which measurable hence it actually shows the degree of accuracy to which an instrument can work. The least count of a screw gauge is represented as: Least Count = Pitch of the screw / No. Of divisions on the circular scale If we are working with the screw whose pitch is ½ mm and the number of divisions on the circular scale is 50 then, using the formula stated above least count for our micrometer is going to be Least Count = 0.5mm / 50 = 0.01mm This means that we can measure up to the 100th part of a mm.

6. CONSTRUCTION OF MICROMETER Frame The body used to hold the anvil and barrel firmly in their place is called frame , in micro meter screw gauges , thick C shaped frames are used . Their mass helps in minimization of expansion or contraction due to temperature some manufacturers also deliver gauges with insulated frames to serve the above mentioned purpose. Anvil It is the fixed part mounted at one end of frame exactly parallel to the moving spindle which move towards it , Anvil face which comes directly in contact to the object being measured is machined extremely fine so to achieve highest degree of precision. Spindle The cylindrical part which displaces by rotation of thimble decreasing the clearance between itself and anvil until the object being measured become stable between the two of them , in modern micrometer screw gauges , anvil and spindle`s open face are tipped with carbide.

7. Sleeve/Barrel the stationary part with having linear scale onto it, called the main scale, it also covers the screw mechanism of screw gauge , now screw gauges are available with adjustable sleeves which makes it easy to eliminate the zero error. Screw :- It is the most important part of instrument because all measurement is done through it in fact. Very fine stainless steel screws are used for this purpose with a definite pitch. Thimble :- It is the part through which measuring screw is rotated, this screwing results in the displacement of spindle and thimble itself. Ratchet; Ratchet is itself a small device which is used to provide a limited applied force , It is installed at the right end of screw gauge , ratchet acts as a safety device for instruments and also adds more precision in measurement . Final adjustment is made by a making three turns of ratchet. Locking Device :- It is actually a nut whose operation is facilitated by means of a lever, usually used to hold tight the spindle at its place so that current reading of that time could be maintained up to a desired length of time. Scales :- Micrometer screw gauge comes with two scales, one rotating scale which can be found on its rotating cylindrical part it is also called circular scale and the other one can be found on its stationary sleeve which is called main scale or sleeve scale , some designs of instrument can also have a vernier scale as well.

8. SOME PROBLEMS