Report About
Engineering Metrology
and Instruments
Mohammed Abd Elghany Abd Elsalam Presented
by
Dr/Mohammed Elshennawy Presented
for
Engineering Metrology & Instruments Course
2nd Industrial Engineering Department
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Emm instruments, Thesis of Manufacturing Processes
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Typology: Thesis
2014/2015
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Report About
Engineering Metrology
and Instruments
Mohammed Abd Elghany Abd Elsalam Presented
by
Dr/Mohammed Elshennawy Presented
for
Engineering Metrology & Instruments Course
2 nd^ Industrial Engineering Department
Engineering Department
โContentโ
โบ Introduction.
- Important concepts.
โบ Measuring Instruments.
1) Length measuring Instruments.
1.1)Rules and tapes.
1.2)Vernier caliper.
1.3)The Micrometer.
1.4)Calipers.
1) Angle measuring Instruments.
2) Gages.
3) Comparative length-measuring instruments.
4.1)Dial indicator.
โบ Table for various Measuring Tools.
Engineering metrology | Eng/ Mohammed Abd 2
Engineering Department can be shown by the spread of shooting of a tar-get (as shown in Diagram below).
- Error: The deviation between the results of measured value to the actual value. - Correction: The numerical value which should be added to the measured value to get the correct result. โ Measurements Standards: Two Standards โ English Speaking Countries (English System): Pound-mass, Foot, Second โ Metric System (SI โ System International): Kilogram, Meter, Second ########################################## ################# โบMeasuring Instruments:
- classification of measuring instruments: Engineering metrology | Eng/ Mohammed Abd 4
Engineering Department 1- Length measuring Instruments.
- Direct measuring.
- Indirect measuring. 1- Angle measuring Instruments. 2- Instruments for surface finish. 3- Instruments for deviations. ููููููููููููููููููููููููููููููููููููููููููููููููููููููููููููููููููููููููููููููููู 1) Length measuring Instruments: 1.1) Rules and tapes: (Direct measuring) Rules and tapes are the simplest way of measuring larger dimensions. Steel rules are generally only available to measure dimensions up to 1 metre. Beyond this, steel tapes (measuring to 30 m) or an ultrasonic rule (measuring to 10m) are used. The steel rule is undoubtedly the simplest instrument available for measuring length. Measurement accuracy is only modest using standard rules, which typically have rulings at 0.5mm intervals, but the best rules have rulings at 0.05mm intervals and a measurement resolution of 0.02 mm. When used by placing the rule against an object, the measurement accuracy is much dependent upon the skill of the human measurer and, at best, the inaccuracy is likely to be at least 0.5%. 1.2) Vernier caliper: (Direct measuring) The vernier calipers found in the laboratory incorporates a main scale and a sliding vernier scale which allows readings to the nearest 0.02 mm. This instrument may be used Engineering metrology | Eng/ Mohammed Abd 5
Engineering Department The micrometer screw gauge is used to measure even smaller dimensions than the vernier calipers. The micrometer screw gauge also uses an auxiliary scale (measuring hundredths of a millimeter) which is marked on a rotary thimble. Basically it is a screw with an accurately constant pitch (the amount by which the thimble moves forward or backward for one complete revolution). Take as an example: the micrometers which have a pitch of 0.50 mm (two full turns are required to close the jaws by 1.00 mm). The rotating thimble is subdivided into 50 equal divisions. The thimble passes through a frame that carries a millimeter scale graduated to 0.5 mm. The jaws can be adjusted by rotating the thimble using the small ratchet knob. This includes a friction ๏ฟฝclutch๏ฟฝ which prevents too much tension being applied. The thimble must be rotated through two revolutions to open the jaws by 1 mm. How to read Micrometer? In order to measure an object, the object is placed between the jaws and the thimble is rotated using the ratchet until the object is secured. Note that the ratchet knob must be used to secure the object firmly between the jaws, otherwise the instrument could be damaged or give an inconsistent reading. The manufacturer recommends 3 clicks of the Engineering metrology | Eng/ Mohammed Abd 7
Engineering Department ratchet before taking the reading. The lock may be used to ensure that the thimble does not rotate while you take the reading.
- Example: The reading is 7.38 mm. In figure shown the last graduation visible to the left of the thimble is 7 mm and the thimble lines up with the main scale at 38 hundredths of amillimeter (0.38 mm); therefore the reading is 7.38 mm. 1.4) Calipers: (Indirect measuring) These are used to transfer the measured dimension from the workpiece to a steel rule. This avoids the necessity to align the end of the rule exactly with the edge of the workpiece and reduces the measurement inaccuracy by a factor of two. In the basic caliper, careless use can allow the setting of the caliper to be changed during transfer from the workpiece to the rule. Hence, the spring-loaded type, which prevents this happening, is preferable. Types of calipers: 1- Inside caliper: are used to measure the internal size of an object. 2- Outside caliper: are used to measure the external size of an object. 3- Divider caliper: are used in the process of marking out suitable workpieces. Engineering metrology | Eng/ Mohammed Abd 8 Inside caliper Outside caliper Divider caliper
Engineering Department frame. When placed on the sloping surfaces of components, rotation of the scale to centralize the bubble in the spirit level allows the angle of slope to be measured. Again, measuring inaccuracies down to ลก 10 minutes of arc are possible if a vernier scale is incorporated in the instrument. Engineering metrology | Eng/ Mohammed Abd 10
Engineering Department
- Gages: Gauge blocks , also known as slip gauges, consist of rectangular blocks of hardened steel that have flat and parallel end faces. These faces are machined to very high standards of accuracy in terms of their surface finish and flatness. The purpose of gauge blocks is to provide a means of checking whether a particular dimension in a component is within the allowable tolerance rather than actually measuring what the dimension is. To do this, a number of gauge blocks are joined together to make up the required dimension to be checked. The pictured below accessories provide a set of holders and tools to extend the usefulness of the gauge block set. They provide a means of securely clamping large stacks together along with reference points and scribers. Slip gauges are made from a select grade of carbide with hardness of 1500 Vickers hardness. Long series slip gauges are made from high Engineering metrology | Eng/ Mohammed Abd 11
Engineering Department (a) Plug gage for checking size or diameter of internally threaded part. (b) Plug gage for checking taper of internally threaded part. (c) Ring gage for checking size or diameter of externally threaded part.
Ring gages:
(a) The Metric Trapezoidal Ring Gage. (b) American Standard Adjustable Ring Gage. Engineering metrology | Eng/ Mohammed Abd 13
Engineering Department
Snap gage:
- Snap gage gages diameters, lengths, and thickness.
- The adjustable limit snap gage is used to check outside diameter.
- There are a various types of snap gages: โ adjustable snap gage. โ adjustable roll snap gage. โ dial indicator snap gage.
- Comparative length-measuring instruments: 4.1) Dial indicator: A dial indicator is used to measure shaft runout, shaft thrust, gear backlash, flywheel face runout, flywheel housing concentricity, and valve seat concentricity. You can mount a dial indicator on a test stand or, with clamps and a magnetic base, directly on the equipment to be Engineering metrology | Eng/ Mohammed Abd 14
Engineering Department โVarious Measuring Toolsโ Word Meaning Context More Information blade micrometer Blade micrometer is a measuring device that has a thin blade to reach inside narrow recesses. The blade micrometer measures narrow grooves and keyways. Blade micrometer is used for measuring where the standard micrometer spindle could not be accommodated. combination set Combination set is used as a rule, a square, a miter, a depth gage, a height gage, and a level. Combination set The combination set consists of: blade, center head, protractor head, combination square head, scribe, and spirit level. comparator Comparator graphically displays and measures dimensions and shapes that would be difficult to measure with regular tools. Also known as shadow graph Optical measurement is a different and valuable aid to quality control. Capable of magnifying an object hundreds of times. Engineering metrology | Eng/ Mohammed Abd 16
Engineering Department depth micrometer Depth micrometer measures depth of holes, slots, and other recesses. Measuring a depth of a slot. These micrometers come as a set with interchangeable rods to accommodate various measurements. dial indicators Dial indicators check alignment of machine components; show the variation of the object being measured. There are 2 types of dial indicators: a. Balanced reading (has figures in both directions from the zero) b. Continuous reading (numbered continuously) Dial indicators can be used to make linear measurements. Continuous reading dial indicator disc micrometer Disc micrometer measures forming tools, cutting edges, narrow slots. The disc micrometer is also called a flange micrometer. This micrometer finds its application in measuring flanges and hard to reach areas. gage block set Gage block set is also known as "Jo Blocks". Precision-round square or rectangular blocks are made of steel, chrome, or tungsten carbide. Gage blocks are used for:
- calibration and inspection of precision instruments
- to set comparators/indicators
- setting of sine bars
- precision layout
- machine setups Engineering metrology | Eng/ Mohammed Abd 17
Engineering Department ring gage A type of "Go" or "No- Go" gage used to admit or refuse the outside dimension being checked. Ring gages are used as sets. There are three types:
- plain ring gages
- taper ring gages
- thread ring gages screw thread micrometer The 60 degree comparator micrometer is usually called a screw thread comparator micrometer or pitch micrometer. Measuring the pitch diameter of a screw thread. The pitch diameter, the most important measurement of a screw thread. sine bar Sine bar is used for checking angles, typically used with gage blocks. Precise angles are measured using the sine bar. The sine bar is a precision bar that has been hardened and then ground and lapped to very precise dimensions. It is also used for machine setups. snap gage Snap gage gages diameters, lengths,and thickness. The adjustable limit snap gage is used to check outside diameter. Various types of snap gages:
- adjustable snap gage
- adjustable roll snap gage
- dial indicator snap gage Engineering metrology | Eng/ Mohammed Abd 19
Engineering Department square A square has two straight edges that form a right angle. A master precision square A machinist uses several types of squares for a variety of jobs. A square is used for inspecting squarness and laying out work. surface gage Surface gage is a scribing tool that draws lines parallel to a surface. When combined with test indicator, flatness, parallelism and heights may be inspected. The surface gage Surface gages are designed for a variety of uses. The main uses are for scribing lines, transferring measurements and for probing surfaces in inspection work. universal bevel protractor Universal bevel protractor is used to lay out, measure, or check angles. The bevel protractor can measure angles to five minutes of a degree. Vernier caliper Vernier caliper is a precision measuring tool capable to read within .001 inch. Used for inside, outside and depth measurements. The Vernier caliper A Vernier caliper consists of a beam with a fixed measuring jaw, a sliding jaw witht he Vernier scale, and a mechanism for making fine adjustments. Engineering metrology | Eng/ Mohammed Abd 20