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

2. 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

3. 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

4. Direct-Reading Instruments
Inside micrometer calipers
Designed for measuring holes, slots and grooves
0.200 to 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

5. 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

6. Inside Micrometers
Used for internal measurements larger than 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 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.

7. 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

8. 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 in
Accuracy: in

9. 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: in. .
Have small, round end or ball
Have flat bottom
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

10. 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

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

12. 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

13. 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 mm
Extensions increase range

14. 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 in. (225 mm)
Screw has range: .500 or in (25mm)
Available with either round or flat rods

15. 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.

16. 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.

17. Vernier Height Gage Precision instrument Variety of sizes:
12-72 in. or mm.
Height within .001 in (0.02 mm)
Digital height gage
zero function, display 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.

18. 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

19. 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

20. To Measure Heights Using Gage Blocks
Gage block buildup made when hole locations must be accurate to 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

21. 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 in (25-mm)
Bar raised or lowered by micrometer thimble graduated by steps in or mm
Can be used for precision inspection and also connected to statistical process control equipment

22. 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