Workshop Technology Measuring Devices PDF

Workshop Technology measuring Devices Dr. Hossam Hamad Dr.Sherine Bishara  Measuring Devices Introduction Some form of precise measurement is necessary if parts are to fit together as intended no matter whether the parts were made by the same person, in the same factory, or in factories a...

Workshop Technology measuring Devices Dr. Hossam Hamad Dr.Sherine Bishara  Measuring Devices Introduction Some form of precise measurement is necessary if parts are to fit together as intended no matter whether the parts were made by the same person, in the same factory, or in factories a long way apart. Spare parts can then be obtained with the knowledge that they will fit a part which was perhaps produced years before. To achieve any degree of precision, the measuring equipment used must be precisely manufactured with reference to the same standard of length.  Measuring Devices We need the measuring tools to perform: a)Calibration. b)Fitting. c)Comparing. Measuring tools must be manufactured according to a standard, then must be used correctly.  Measuring Devices Vernier caliper (Dial & Electronic) Vernier Height Types Of Devices Vernier instruments Vernier Depth (Dial & Electronic) Vernier bevel protractor External Micrometer Depth  Measuring Devices Vernier instruments All instruments employing a vernier consist of two scales: a) Vernier scale (moving): is divided into 50 equal parts which occupy the same length as 49 divisions or 49 mm. b) Fixed scale: is graduated in millimeters, every 10 divisions equaling 10 mm. Five divisions represent 5 × 0.02 = 0.1 mm. Every fifth division on this scale is marked 1 representing 0.1 mm, 2 representing 0.2 mm and so on (Fig. 6.1).  Measuring Devices To take a reading: a) Note how many millimeters the zero on the vernier scale is from zero on the fixed scale. b) Note the number of divisions on the vernier scale from zero to a line which exactly coincides with a line on the fixed scale. Measuring Devices Vernier caliper Measuring Devices Vernier caliper Measuring Devices Vernier caliper Measuring Devices Dial caliper Measuring Devices Electronic caliper Measuring Devices Vernier height gauge Measuring Devices Vernier depth gauge Measuring Devices Dial depth gauge Measuring Devices Electronic depth gauge Measuring Devices Vernier bevel protractor Measuring Devices Micrometers Measuring Devices Micrometers Measuring Devices Electronic external micrometer Measuring Devices Depth micrometer  Measuring Devices Direct reading digital depth micrometer  Measuring Devices Dial indicators Dial indicators magnify small movements of a plunger or lever and show this magnified movement by means of a pointer on a graduated dial. This direct reading from the pointer and graduated dial gives the operator a quick, complete and accurate picture of condition of the item under test. The mechanism of a dial indicator is similar to that of a watch and, although made for workshop use, care should be taken to avoid dropping or knocking it in any way. Slight damage to the mechanism can lead to sticking which may result in incorrect or inconsistent readings.  Measuring Devices Dial indicators Dial indicators are used to: Check the dimensional accuracy of work pieces in conjunction with other equipment such as gauge blocks Check straightness and alignments of machines and equipment Set work pieces in machines to ensure parallelism and concentricity and for a host of other uses too numerous to list completely.  Measuring Devices Plunger-type instruments The most common instrument of this type is: The vertical plunger It carries a rack which operates a system of gears for magnification to the pointer. Plunger-type dial indicator  Measuring Devices In conjunction with a robust stand or surface gauge. this instrument can be used to check straightness, concentricity, as well as workpiece heights and roundness. Dial test indicator and stand  Measuring Devices Lever-type instruments The lever-type of instrument is shown in Fig. Due to the leverage system, the range of this type is not as great as that of the plunger-type and is usually 0.5 or 0.8 mm. Lever-type dial indicator