Most bore gauges consist of a dial indicator,extension pieces, bezel and locknut, spring-loadedguide, and sensor button.Before you start a measuring procedure, exposeboth the bore gauge and the master ring gauge, or anyother tools used to preset the bore gauge, and the part tobe measured to the same work place environment forone hour. If you fail to do this, a temperature differentialmay cause your readings to be inaccurate. When you usethe bore gauge, touch only its insulated handle.The gauge has two stationary spring-loaded pointsand an adjustable point to permit a variation in range.These points are evenly spaced to allow accuratecentering of the tool in the bore. A fourth point, the tipof the dial indicator, is located between the twostationary points. By simply rocking the tool in the bore,you can observe the amount of variation on the dial.Figure 2-7 shows a bore gauge inside a bore beingmoved in a gentle rocking motion. Always follow thebore gauge manufacturer’s operating manual. Measurethe bore and mark the areas you measure. A goodFigure 2-7.—Measuring a bore with a bore gauge.practice is to check the bore gauge in the standard afteryou take each set of measurements to ensure thatreadings are accurate.STRAIN/DEFLECTION GAUGEA strain or deflection gauge is used to check thecrankshaft alignment on large diesel engines. It is aspecially adapted dial indicator that fits between thecrank webs. The strain gauge reads the flexing motionof the webs directly as the crankshaft is slowly rotated(correct engine rotation). The gauge dial reads in0.00l-inch graduations.The strain gauge consists of a dial indicator, contactpoint, balancing attachment, clamping nut, springplunger, rods and extension, and bezel.Before you take a reading, be sure the engine iscompletely assembled and cold. Place the strain gaugebetween the webs of a crankthrow, as far as possiblefrom the axis of the crankpin. The ends of the indicatorshould rest in the prick-punch marks in the crank webs.If these marks are not present, consult themanufacturer’s technical manual for the proper locationof the marks. Ensure that the strain gauge is at the sametemperature as the engine. A temperature differentialmay cause inaccurate readings. Readings are generallytaken at the four crank positions; top dead center,inboard, near or at bottom dead center, and outboardHowever, the manufacturer’s technical manual for thespecific engine provides information concerning theproper positions of the crank for taking readings. Insome situations, due to the position of the dial, you mayneed to use a mirror and a flashlight to read the gauge.Once you have placed the indicator in position for thefirst reading, DO NOT touch the gauge until you havetaken and recorded all four readings. Variations in thereadings taken at the four crank positions indicatedistortion of the crank, which may be caused by any ofseveral factors, such as a bent crankshaft, worn bearings,or improper engine alignment. The manufacturer’stechnical manual will provide you with the maximumallowable deflection. Figure 2-8 shows the locations fortaking crankshaft deflection readings.BORESCOPEA borescope is used to inspect internal parts on anengine without having to disassemble the engine. Thisinstrument helps a great deal in estimating the amountof repair work needed and the time required for therepair. Figure 2-9 shows a typical borescope.2-5
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business