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WORKSHOP PRACTICE

WORKSHOP PRACTICE. LAB No. 2 Measuring Tools. Today’s LAB. Measuring Tools Vernier Caliper Micrometer SWG. Measurement. Measurement means to compare something with standard. E.g. measuring length of a wire, diameter of a cylinder, depth of any object.

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WORKSHOP PRACTICE

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  1. WORKSHOP PRACTICE LAB No. 2 Measuring Tools

  2. Today’s LAB • Measuring Tools • Vernier Caliper • Micrometer • SWG

  3. Measurement Measurement means to compare something with standard. E.g. measuring length of a wire, diameter of a cylinder, depth of any object. The SI unit of length is meter (base unit). Its multiples and sub-multiples are given in the table.

  4. Meter and its sub-multiples

  5. Meter and its multiples

  6. Measuring Tools • Vernier caliper • Vernier caliper is a measuring device used to measure precise increments between two points. • Micrometer • Micrometer is a measuring device used for precisely measuring thickness, inner and outer diameter, depth of slots. • SWG • A gauge for measuring the diameter of wire, usually consisting of a long graduated plate with similar slots along its edge.

  7. Vernier caliper • Function • To measure smaller distances • Can measure up to .001 inch or .01mm. • Features • Larger, lower jaws are designed to measure outer points e.g. diameter of a rod. • Top jaws are designed to measure inside points e.g. size of a hole. • A rod extends from the rear of the caliper and can be used to measure the depth.

  8. Structure of Vernier caliper

  9. Structure of the Vernier caliper • Main Scale • Main scale is graduated in cm and mm. • Vernier Scale • It slides on the main scale. • On Vernier scale 0.9cm is divided into 10 equal parts. • Jaws • Two inside jaws (Upper) • Two outside jaws (Lower)

  10. Least Count • Least count (L.C) is the smallest reading we can measure with the instrument. • L.C = one main scale division – one vernier scale division L.C = 1mm – 0.09mm L.C = 0.1mm = 0.01cm • Least Count = Value of the smallest division on MS/ Total number of division on VS L.C = 1mm / 10 = 0.1 cm / 10 = 0.01cm

  11. How to use Vernier caliper? • Close the jaws • Calculate the least count • Place the object between the two jaws • Record the position of zero of Vernier scale on the Main scale (3.2cm) • Notice the reading of VS which coincides with MS reading (3rd division in this case)

  12. Reading of the Instrument Reading of the instrument = MS div + (coinciding VS div x L.C) = 3.2 + (3 x 0.01) = 3.2 + 0.03 = 3.23 cm

  13. Sample Picture

  14. To measure the depth A rod extends from the rear of the caliper and can be used to measure the depth. Open the jaws of caliper and place the rod inside hole of the object, such as the rod reaches the inner most portion of the object. Read the Vernier caliper. (same procedure as described in previous slides)

  15. Micrometer • Function • Micrometer allows the measurement of the size of the body i.e. thickness, depth, inner/outer diameter. • Features • Two jaws (one fixed, one movable) • Spring loaded twisting handle • Easy to use and more précised • Can measure up to .001cm

  16. Structure of the Micrometer

  17. Structure of Micrometer • Jaws • 2 jaws (one fixed, one movable) • Circular Scale • Movable jaw is attached to a screw, scale on this screw is called Circular scale. • Either 50 or 100 divisions • Linear Scale • Horizontal Scale

  18. Structure of Micrometer • Frame • The C-shaped body that holds the anvil and sleeve in constant relation to each other. • Anvil • The jaw which remains stationary. • Spindle • The jaw which moves towards the anvil. • Lock Nut • A lever, one can tighten to hold the spindle stationary. • Sleeve • The stationary round part with the linear scale on it. (Main Scale) • Thimble • Thimble rotates around the sleeve. • Ratchet Stop • Device on end of handle that limits applied pressure by slipping at a calibrated torque.

  19. Pitch of Micrometer • When the head of the micrometer rotate through one rotation, called pitch of the micrometer. • The screw moves forward or backward 1mm on the linear scale. • Pitch of Micrometer = distance on linear scale / one rotation Pitch of Micrometer = 1/1 = 1mm

  20. Least Count Least Count = Pitch of the Micrometer / Total number of circular scale division Least Count = 1 / 100 = 0.01mm = 0.001cm

  21. How to use Micrometer? • Thimble • The thimble rotates around a cylinder which is marked in millimeters. • The left-hand side of the thimble has markings all around it. • The line labeled 0 is the primary pointer. • Close the jaws • Calculate the least count • Place the object between the two jaws • Record the position of main scale where the two measuring rods met. • Note the position of the circular scale which coincides with main scale

  22. Reading of the Instrument Reading of the instrument = MS div + (coinciding CS div x L.C) = 8+ (12 x 0.01) = 8 + 0.120mm = 8.120 mm = 8120 µm

  23. Standard Wire Gauge (SWG) A gauge for measuring the diameter of wire, usually consisting of a disk having variously sized slots in its periphery or a long graduated plate with similar slots along its edge. A standardized system of wire sizes. Wires are manufactured to standard sizes and labeled with their SWG. As the SWG increases the diameter decreases.

  24. SWG

  25. Lab Reports • Last date of submission of Lab 1 & 2 is Wednesday, 4th November till 1: 00 p.m. in Workshop lab.

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