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![]() Measurement, Test and Calibration
![]() How to calibrate Dial Indicator
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| Author | Topic: How to calibrate Dial Indicator |
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brossbach unregistered |
Can someone show me how or explain step by step how to calibrate a dial indicator the correct way. I'm having problems how to calibrate correctly. I need help!!!!!!!! IP: Logged |
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Jerry Eldred Forum Wizard Posts: 136 |
I can give you the basics here. If you will contact me via email, I can probably scrounge up a procedure. There is differing opinions as to whether or not dial indicators even need calibration, as they are a relative indicator (delta measurements only, and not absolute length measurement). Even the Air Force has a variety of recommendations. One of these is just to check the repeatability and smooth action of the gears, as they don't "drift", only get worn or broken. To calibrate you need a gauge stand, a surface plate, and appropriately sized gage blocks. The dial indicator is mounted on a gage stand on the surface plate, a zero is set on the dial, then gage blocks are inserted, and dial indicator reading is taken to determine that it is functioning properly. Check for smooth easy movement of the measuring rod on the indicator. That's an over-simplified version of the method. If you email, I can look to see if I have a procedure. Send me manufacturer and model of the indicators you are calibrating. ------------------ IP: Logged |
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AJLenarz Forum Contributor Posts: 25 |
Bossbach, I donât consider myself a gage calibration guru. Ultimately you need to develop a calibration procedure that fits your companyâs needs. Below is just an example of a calibration procedure I have observed elsewhere. Vertically operating dial indicators will be checked for accuracy and repeatability using a precision bench micrometer in a horizontal position (a special holding fixture may be constructed for the purpose). The horizontal test type indicator may be checked for accuracy and repeatability using the micrometer height gage or gage block stack-ups. In addition each indicator will be inspected for smoothness of operation, spindle looseness, proper spring tension and backlash in reversing direction. The following steps must be taken in inspecting dial indicators: 1) Check for sticking. Move the spindle slowly from the rest position to the maximum limit of travel and return by means of hand pressure. Test Indicator: Mount the indicator on a surface gage or height gage and zero the indicator to zero on the micrometer height master. Rotate the micrometer head to different points and note whether the changes in the indicator are the same as shown on the micrometer head. Reverse direction of the micrometer head and check at different points in the opposite direction, note whether there is any backlash and report results on the calibration record. Acceptance limits: Each indicator must meet the following requirements. A) The spindle is not to stick at any point across the entire range of the indicator. B) Spindle play and rack pin side play must not exceed 0.0002 inch deflection in the dial reading. C) There is to be no excessive spring pressure. Accuracy of calibration will be within plus or minus one unit of graduation at any point covering the entire range of the indicator. The indicator is to repeat to zero at rest. On indicators graduated to 0.0001 inch or less the acceptable tolerance for this requirement is one graduation. On indicators where the graduations are 0.0005 inch or more the tolerance is 0.0002 inch. IP: Logged |
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DICKIE Forum Contributor Posts: 46 |
I agree with what everyone has been said but would like to add that for the first 2 1/2 revolutions of indicator reading measurements should take place every quarter turn to check pinion gear and transfer gear accuracy. Then measurements can be taken at several intervals up to full scale, this will verify accuracy of the rack. This holds true for all dial gages. (calipers, bore gages, etc). IP: Logged |
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Ryan Wilde Forum Contributor Posts: 20 |
You might want to get ahold of a copy of ANSI B89.1.10M, which states all of the accuracy, repeatability, and hysteresis (backlash) tolerances. The height stand method works well, but fails to provide hysteresis (backlash) data, which may be fine as long as you aren't performing runout type measurements which require ascending and descending measurements. Ryan IP: Logged |
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Jeremy S unregistered |
DIAL / DIGITAL INDICATORS(Spindle Type) Calibration Frequency: 12 months 1.0 Scope: 2.0 References: This document is based on the NAVAIR procedure. 4.0 General Requirements: Stabilization: Preliminary Operations: Standards and Calibrating Equipment: 5.0 Equipment:The following equipment is considered a minimal requirement and any 1. Grade 0 Gage Blocks. 6.0 Calibration Process: Use only the portion of the calibration method applicable Item Test Characteristics Acceptance Limits Test Method 1 Graduations Good contrast Visual 2 Wear of gaging tip No flat on spherical Magnifying glass 3 Repeatability Manufacturerâs specifications Gage block 4 Linearity Manufacturerâs specifications Gage block Example of a dial indicator Resolution Reading Range Test: Inward Outward 7.0 Notes: 1. Record readings, maintenance such as servicing, adjustment, repairs IP: Logged |
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