Lecture 02MEC 263 ArijitSen Faculty Department of Mechanical Engineering IUBAT
Linear Measurement • Line graduated measuring instruments incorporate graduation spacing representing known distance. Some measurement tools are: • Steel rule • Caliper • Surface plate • Angle plate • V-Block • Spirit level • Feeler gauge • Vernier instruments • Slip Gauge
Steel Rule • A ruler, sometimes called a rule or line gauge, is an instrument used in geometry, technical drawing, printing and engineering/building to measure distances and/or to rule straight lines. • Strictly speaking, the ruler is essentially a straightedge used to rule lines, but typically the ruler also contains calibrated lines to measure distances
Caliper • Calliper is a device used to measure the distance between two opposing sides of an object. • A caliper can be as simple as a compass with inward or outward-facing points. • The tips of the caliper are adjusted to fit across the points to be measured, the caliper is then removed and the distance read by measuring between the tips with a measuring tool, such as a ruler.
Inside caliper Theinside calipersare used to measure the internal size of an object. Outside caliper Outside calipers are used to measure the external size of an object.
Oddleg caliper Oddleg calipers,Hermaphrodite calipersorOddlegjennys, as pictured on the left, are generally used to scribe a line a set distance from the edge of a workpiece. The bent leg is used to run along the workpiece edge while the scriber makes its mark at a predetermined distance, this ensures a line parallel to the edge.
Divider caliper In the metalworking fielddivider calipersare used in the process ofmarking outsuitable workpieces. The points are sharpened so that they act as scribers, one leg can then be placed in the dimple created by acenter or prick punchand the other leg pivoted so that it scribes a line on the workpiece's surface, thus forming an arc or circle.
Surface plates • A surface plate is a solid, flat plate used as the main horizontal reference plane for precision inspection, marking out (layout), and tooling setup. • The surface plate is often used as the baseline for all measurements to the workpiece, therefore one primary surface is finished extremely flat with accuracy up to .00001"/.00025 mm for a grade AA or AAA plate. • Surface plates are a very common tool in the manufacturing industry and are often permanently attached to robotic type inspection devices such as a coordinate-measuring machine.
Angle Plate • An angle plate is a work holding device used as a fixture in metalworking. • The angle plate is made from high quality material (generally spheroidal cast iron) that has been stabilized to prevent further movement or distortion. Slotted holes or T bolt slots are machined into the surfaces to enable the secure attachment or clamping of workpieces to the plate, and also of the plate to the worktable. • Angle plates also may be used to hold the workpiece square to the table during marking out operations. • Adjustable angle plates are also available for workpieces that need to be inclined, usually towards a milling cutter.
Adjustable angle plate Normal Angle Plate
V-Block • They are widely used for workshop and inspection purpose for checking out the roundness of cylindrical workpieces and for making centers accurately. • Generally the angle of V is 900 and these are available of wide variety of shapes. • Sometimes clamps are provided which bridge the Vee to secure the work.
Spirit Level • A spirit level or bubble levelis an instrument designed to indicate whether a surface is horizontal (level) or vertical (plumb). • Different types of spirit levels may be used by carpenters, stonemasons, bricklayers, other building trades, workers, surveyors, millwrights and other metal workers and in some photographic and videographic work.
Original spirit levels had two banana-shaped curved glass vials at each viewing point and were much more complicated to use. • In the 1920s, Henry Ziemann invented the modern level with a single vial. • These vials, common on most ordinary levels today, feature a slightly curved glass tube which is incompletely filled with a liquid, usually a colored spirit or alcohol, leaving a bubble in the tube. • At slight inclinations the bubble will travel away from the center position, which is usually marked in some manner.
Alcohols such as ethanol are often used rather than water for a variety of reasons. • Alcohols generally have very low viscosity and surface tension, which allows the bubble to travel the tube quickly and settle accurately with minimal interference with the glass surface. • Alcohols also have a much wider liquid temperature range, and won't break the vial as water could due to ice expansion. • A colorant such as fluorescein, typically yellow or green, may be added to increase the visibility of the bubble.
Feeler Gauge • A feeler gauge is a tool used to measure gap widths. Feeler gauges are mostly used in engineering to measure the clearance between two parts. • They consist of a number of small lengths of steel of different thicknesses with measurements marked on each piece. • They are flexible enough that, even if they are all on the same hinge, several can be stacked together to gauge intermediate values. It is common to have two sets for imperial units (typically measured in thousandths of an inch) and metric (typically measured in hundredths of a millimeter) measurements.
A similar device with wires of specific diameter instead of flat blades is used to set the gap in spark plugs to the correct size; this is done by increasing or decreasing the gap until the gauge of the correct size just fits inside the gap. • The lengths of steel are sometimes called blades, although they have no sharp edge
Vernier Instruments • Vernier instruments are those having vernier scale in it. • The principle of vernier is that when two scales or divisions of slightly different sizes are used the difference between them can be utilized to enhance the accuracy of measurement. • Example vernier caliper, micrometer, height gauge etc.
VernierCaliper Virnier dial caliper
Digital Calliper Height Gauge Micrometer
Slip Gauge • A gauge block (also known as a gage block, Johansson gauge, slip gauge, or Jo block)is a precision ground and lapped length measuring standard. • Invented in 1896 by Swedish machinist Carl EdvardJohansson,they are used as a reference for the calibration of measuring equipment used in machine shops, such as micrometers, sine bars, calipers, and dial indicators (when used in an inspection role). • Gauge blocks are the main means of length standardization used by industry.
Each gauge block consists of a block of metal or ceramic with two opposing faces ground precisely flat and parallel, a precise distance apart. • Standard grade blocks are made of a hardened steel alloy, while calibration grade blocks are often made of tungsten carbide or chromium carbide because it is harder and wears less. • Gauge blocks come in sets of blocks of various lengths, along with two wear blocks, to allow a wide variety of standard lengths to be made up by stacking them. • The length of each block is actually slightly shorter than the nominal length stamped on it, because the stamped length includes the length of one wring film, a film of lubricant which separates adjacent block faces in normal use. This nominal length is known as the interferometric length.
In use, the blocks are removed from the set, cleaned of their protective coating (petroleum jelly or oil) and wrung together to form a stack of the required dimension, with the minimum number of blocks. • Gauge blocks are calibrated to be accurate at 68 °F (20 °C) and should be kept at this temperature when taking measurements. • This mitigates the effects of thermal expansion. The wear blocks, made of a harder substance like tungsten carbide, are included at each end of the stack, whenever possible, to protect the gauge blocks from being damaged in use.
As a general principle, machinists and toolmakers try to use a stack with the fewest number of blocks possible, because avoiding stacking the blocks avoids stacking their size errors cumulatively. Thus a stack totaling 6.38 that is composed of 2 blocks (a 5.00 block wrung to a 1.38 block) is preferable to a stack also totaling 6.38 that is composed of 4 blocks (such as a 2.00, 1.49, 1.48, and 1.41 all wrung together). However, the stacked error is still small enough that it is often negligible in all but the most demanding contexts of use; so "violations" of this principle are usually not a problem when necessary. In a busy shop, some of the blocks will be in use elsewhere, so one creates a stack from the blocks available at the time. Typically the few millionths of an inch difference will not be detectable, or matter, in the context. Contexts demanding ultimate precision are rarer and more expensive.
Set of 103 Pieces; contains 49 pieces with a range of 1.01 mm to 1.49mm in steps of 0.01mm; 49 pieces with a range of 0.50 mm to 24.50mm in steps of 0.50mm; 4 pieces of 25, 50, 75 and 100mm respectively and 1 piece extra of 1.005 mm
List the slips to be wrung together to produce an overall dimension of 92.375 mm using two protection slip of 2.500mm.