Inside-, Depth-, and Height-Measuring Instruments Unit 11

Objectives Measure hole diameters to within .001-in. (0.02-mm) accuracy using inside micrometers and inside micrometer calipers Measure depths of slots and grooves to an accuracy of .001 in. (0.02 mm) Measure heights to an accuracy of .001 in. (0.02 mm) using a vernier height gage

Inside-Measuring Instruments Two Categories Direct-reading Size of hole read on instrument used to measure hole Most common: inside micrometer, Intrimik, vernier caliper Transfer-type Set to diameter of hole then size transferred to an outside micrometer to determine actual size Most common: inside calipers, small hole gages, telescope gages

Direct-Reading Instruments Inside micrometer calipers Designed for measuring holes, slots and grooves 0.200 to 2.000 in or 5-50 mm Nibs of jaws hardened and ground to small radius Permit accurate measurement Locking nut used to lock at desired size Based on same principle as standard micrometer Special-purpose tools not used in mass production

To Use an Inside Micrometer Caliper Adjust jaws to slightly less than diameter to be measured Hold fixed jaw against one side of hole and adjust movable jaw until proper "feel" Move movable jaw back and forth to ensure measurement taken is across true diameter Set lock nut, remove instrument and check reading

Inside Micrometers Used for internal measurements larger than 1.500 in. or 40 mm. Set consists of Micrometer head with range of .500 or 1 in. Several extension rods of different lengths .500 in. spacing collar Set cover range 1.5000 to over 100 in. Large sets have hollow rods for strength Read same manner as standard micrometer Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

To Measure with Inside Micrometer Measure size of hole with rule Insert correct extension rod Align zero marks on rod and micrometer head Hold rod firmly against head, tighten knurled set screw Adjust micrometer to slightly less than diameter to be measured Hold head in fixed position, adjust micrometer to hole size while moving rod end in arrow direction Remove micrometer and note reading Add length of extension rod and collar

Intrimik Consists of head with three contact points spaced 120º apart attached to micrometer Contact points forced out to contact inside of hole Self-centering Provides direct reading Range: .275 to 12.000 in Accuracy: .0001 - .0005 in

Transfer-Type Instruments Size of object taken with instrument not capable of giving direct reading Small hole gages for small measures Sets of four Range: .125 - .500 in. . Have small, round end or ball Have flat bottom Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

To Use Small Hole Gage Require extreme care in setting Measure hole with rule Select proper small hole gage Clean hole and gage Adjust gage slightly smaller than hole and insert Adjust gage till touching sides of hole or slot Swing handle back and forth ("feel") and adjust knurled end Remove gage, check size with outside micrometer

Transfer-Type Instruments Telescope Gages Used to obtain size of holes, slots, and recesses from .3125 to 6.000 in. (8 to 152 mm) T-shaped: pair of telescoping tubes connected to handle Knurled knob on handle end locks plungers into position

To Measure Using a Telescope Gage Measure hole size and select gage Clean gage and hole Depress plungers until smaller that hole Insert into hole, release plungers Lightly snug up knurled knob Hold bottom leg in position and move handle downward through center, move top leg from side to side Tighten knurled knob to lock plunger position Recheck "feel" on gage Check gage size with outside micrometers

Dial Bore Gages Used to check hole diameters and bores for size, out-of-round, taper, bellmouth, hourglass, or barrel shapes Gaging accomplished by three spring-loaded centralizing plungers in head One actuates dial indicator ten-thousands of inch or 0.01 mm graduations Six sizes cover range 3-12 in or 75-300 mm Extensions increase range

Micrometer Depth Gage Used for measuring depth of blind holes, slots, recesses, and projections Consists of flat base attached to micrometer sleeve Extension rod of required length fits through sleeve and protrudes through base Held in position by threaded cap on top of thimble Come in various lengths up to 9.000 in. (225 mm) Screw has range: .500 or 1.000 in (25mm) Available with either round or flat rods

To Measure with a Micrometer Depth Gage Remove burrs from edge of hole and face Clean work surface and base of micrometer Hold micrometer base against work surface Rotate thimble lightly until bottom of extension rod touches bottom of hole Recheck micrometer setting Carefully not reading Numbers on thimble and sleeve are reverse of standard micrometer.

Checking position of toolmaker's buttons using a vernier depth gage Measures depths of holes, slots and recesses Read same as standard vernier caliper Checking position of toolmaker's buttons using a vernier depth gage Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Vernier Height Gage Precision instrument Variety of sizes: 12-72 in. or 300-1000 mm. Height within .001 in (0.02 mm) Digital height gage zero function, display .0001 in. Offset scriber Attachment that permits setting heights from face of plate Depth gage attachment Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

To Measure with a Vernier Height Gage and Dial Indicator Thoroughly clean plate, base, work surface Place finished edge of work on surface plate Clamp against angle plate if necessary Insert snug-fitting plug into hole with .500 in projecting Mount dial indicator on movable jaw Adjust movable jaw until indicator almost touches surface plate

To Measure with a Vernier Height Gage and Dial Indicator Lock upper slide of height gage, use adjusting nut to move indicator until dial registers ¼ turn Set indicator dial to zero Adjust vernier height gage until indicator registers zero on top of plug Subtract initial reading plus half diameter of plug

To Measure Heights Using Gage Blocks Gage block buildup made when hole locations must be accurate to .0005 in. (0.010 mm) Procedure Prepare required gage block buildup Mount suitable dial indicator on surface or vernier height gage Set dial indicator to zero on top of gage blocks Move indicator over top of plug Difference between gage block buildup and top of plug

Precision Height Gage Provides quick and accurate method of setting any height within range of instrument Eliminates need for calculating and assembling gage blocks Surface plate used as reference surface Made from hardened, ground round steel bar Measuring steps spaced at 1.000-in (25-mm) Bar raised or lowered by micrometer thimble graduated by steps .0001 in or 0.002 mm Can be used for precision inspection and also connected to statistical process control equipment

To Use Precision Height Gage Clean surface plate and feet of height gage Clean bottom of work, place on surface plate Insert plugs into holes to be checked Mount dial indicator on movable jaw Adjust height gage until dial registers .015 in. Turn dial of indicator to zero Move dial indicator over nearest disk and raise column by turning micrometer until dial equals zero Check micrometer reading (distance from plate to top of plug) Subtract half diameter of plug from reading