1. Comparison Measurement Session 14

2. Comparison Measurement • Process consisting of comparing measurement of part to known standard or master of exact dimension required • Comparators • Any instrument used to compare size of workpiece to known standard • Incorporate some means of amplification to compare part size to set standard • Standard usually gage blocks

3. Dial Indicators • Used to compare sizes and measurements to known standard and check alignment of machine tools, fixtures, and workpieces prior to machining • Many work on gear and rack principle • Rack cut on plunger or spindle is in mesh with a pinion which is connected to a gear train • Any movement of spindle magnified and transmitted to pointer over graduated dial

4. Dial Indicators • Generally two types • Continuous-reading dial indicator • Numbered clockwise for 360º • Regular-range • Only 2 ½ revolutions • Long-range indicator • Digital and used to indicate table travel

6. Dial Indicators • Generally two types • Dial test indicator • Reads both right and left from 0 • Equipped with tolerance pointers

8. Dial Test Indicators • Perpendicular dial test indicators • Have spindle at right angles to dial • Used in setting up lathe work, table alignment • Universal dial test indicator • Has contact point that may set through 180º arc • Used to check internal and external surfaces

9. Dial Test Indicators

10. Dial Test Indicators

11. Dial Test Indicators

12. Electronic Dial Indicators • Generally Round Face • Regular-range • One inch • 25 millimeters • Accuracies • Typically 0.000 05 in • Typically 0.000 1 mm

13. Electronic Dial Indicators

15. Indicator Magnetic Base Stand • Manual Indicator • Height adjustable • Magnetic Base • Allows setting indicator at different angles or positions

16. Indicator Magnetic Base Stand

17. Indicator Magnetic Base Stand

18. Dial Indicator Inspection Stand • Electronic Indicator • Height adjustable • Accommodates various size parts • Base Precision machined or ground granite

19. Dial Indicator Inspection Stand

20. Dial Indicator Inspection Stand

21. Measuring with a Dial Test Indicator and Height Gage • Clean face of surface plate and height gage • Mount dial indicator on movable jaw • Lower movable jaw until indicator point just touches top of gage block resting on surface plate • Tighten upper locking screw on vernier and loosen lower locking screw

22. Measuring with a Dial Test Indicator and Height Gage • Carefully turn adjusting nut until indicator needle registers ¼ turn • Turn bezel to set indicator to zero • Note reading on height gage and record it • Raise indicator to height of first location to measure

23. Measuring with a Dial Test Indicator and Height Gage • Adjust height gage until indicator reads zero • Note height gage reading againand record it • Subtract first reading from second