TECHNICAL MANUAL INSTRUMENT CALIBRATION PROCEDURE THREAD RING GAGES THIS PUBLICATION SUPERSEDES NAVAIR 17 20MD 143L DATED 1 OCTOBER 1992

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1 TECHNICAL MANUAL INSTRUMENT CALIBRATION PROCEDURE THREAD RING GAGES THIS PUBLICATION SUPERSEDES NAVAIR 17 20MD 143L DATED 1 OCTOBER 1992 DISTRIBUTION STATEMENT C. DISTRIBUTION AUTHORIZED TO U.S. GOVERNMENT AGENCIES AND THEIR CONTRACTORS TO PROTECT PUBLICATIONS REQUIRED FOR OFFICIAL USE OR FOR ADMINIS- TRATIVE OR OPERATIONAL PURPOSES ONLY. OTHER REQUESTS FOR THIS DOCUMENT SHALL BE RE- FERRED TO NAVY MEASUREMENT SCIENCE DIRECTORATE, NAVAL WARFARE ASSESSMENT DIVISION, P.O. BOX 5000 CORONA, CA DESTRUCTION NOTICE FOR UNCLASSIFIED, LIMITED DOCUMENTS, DESTROY BY ANY METHOD THAT WILL PREVENT DISCLOSURE OF CONTENTS OR RECONSTRUCTION OF THE DOCUMENT. PUBLISHED BY DIRECTION OF COMMANDER NAVAL AIR SYSTEMS COMMAND 1 JUNE 1994

2 LIST OF EFFECTIVE PAGES Insert latest changed pages; dispose of superseded pages in accordance with applicable regulations. : On a changed page, the portion of the test affected by the latest change is indicated by a vertical line, or other change symbol, in the outer margin of the page. Changes to illustrations are indicated by miniature pointing hands. Changes to wiring diagrams are indicated by shaded areas. Page No. Change No. * Change Date Page No. Change No. * Change Date Title 0 A 0 i 0 1 to (blank) 0 15, 16 0 A 1 0 * Zero in this column indicates an original page. A

3 TABLE OF CONTENTS Section Page 1 Introduction and Description Equipment Requirements Preliminary Operations Calibration Process Thread Ring Gage Tests Lead and Pitch Diameter Minor Diameter Effective Minor Diameter Flank Angle Root Clearance Navy Calibration Checklist Appendix A: Representative Test Instruments A 1 ILLUSTRATIONS Figure Page 1 Thread Ring Gage Effective Minor Diameter Test Configuration TABLES Table Page 1 Calibration Description i

4 SECTION 1 INTRODUCTION AND DESCRIPTION 1.1 This procedure describes the calibration of X tolerance thread ring gages conforming to the 60 thread form. Thread ring gages are mainly used for the inspection of external screw threads, or products containing such threads. Ring gages conforming to a tapered design or to a thread form other than the American National/Unified 60 thread form are not addressed in this procedure; W tolerance thread ring gages including the 60 thread form are also not addressed in this procedure. However, similarities in checking or testing the various types described herein are acknowledged. Gages that can be calibrated using this procedure include, but are not limited to, the models and series listed in Appendix A. The gage being calibrated is referred to herein as the TI (Test Instrument). 1.2 All comments concerning this procedure should be directed to Navy Measurement Science Directorate, Naval Warfare Assessment Division, P.O. Box 5000, Corona, CA This procedure includes tests of essential performance parameters only. Any malfunction noticed during calibration, whether specifically tested for or not, should be corrected. TI Characteristics Table 1. Calibration Description Performance Specifications Test Method Thread ring gage Lead Pitch diameter *Minor diameter *Effective minor diameter Range: up to in. Tolerance: up to in. Range: 0.05 up to 6 in. Tolerance: up to in. Range: 0.04 up to 6 in. Tolerance: up to in. Range: 0.04 up to 6 in. Tolerance: up to in. Not measured directly; correct lead determined by a satis factor fit with both the truncated and full form portions of the appropriate thread setting plug. Same as above, except as applicable to pitch diameter. Not measured directly; correct diameter determined by entry and no entry of appropriate GO and NOT GO cylindrical plain plug gages. The thread setting plug corresponding to the TI size is mounted in a vee block. The height of the plug centerline is determined from measurements of a thread measuring wire placed on top of the plug. The TI is then screwed onto the plug and the height of the TI minor 1

5 TI Characteristics Effective minor diameter (cont.) Flank angle *Root clearance Performance Specifications Range point: 30 deg. of arc Tolerance: 4 up to 30 min. of arc Range: up to in. Tolerance: up to min. (sharp V) up to max. (V w/undercut) Test Method diameter at its lowest point is measured as the TI is rotated on the plug. The measured value can then be compared to the calculated minimum effective minor diameter (E.M.D.). A cast is made of the TI interior thread area. The cast is then removed and the flank angle is measured in the same manner as on a thread plug gage, in accordance with NAVAIR 17 20MD 141L. The test is not required if the lead, pitch diameter, and minor diameter test results were satisfactory. Same as above. *Test is required only upon initial acceptance or if suspect. SECTION 2 EQUIPMENT REQUIREMENTS Minimum use specifications are the principal parameters required for performance of the calibration, and are included to assist in the selection of alternate equipment, which may be used at the discretion of the using laboratory. Satisfactory performance of alternate items shall be verified prior to use. All applicable equipment must bear evidence of current calibration. The instruments utilized in this procedure were selected from those known to be available at Navy calibration facilities, and the listing by make or model number carries no implication of preference, recommendation, or approval for use by other agencies. It is recognized that equivalent equipment produced by other manufacturers may be capable of equally satisfactory performance in this procedure. 2

6 Item 2.1 Truncated thread setting plug, W tolerance 2.2 Stoddard solvent 2.3 Cylindrical plain plug gage, X tolerance 2.4 Height indicator, gage block 2.5 Height indicator, electronic 2.6 Height gage 2.7 Vee blocks (up to 6 ea.) 2.8 Surface plate 2.9 Sealing compound 2.10 Arkansas stone 2.11 Optical comparator 2.12 Modeling clay 2.13 Dental plaster Minimum Use Specifications Range: Lead: up to in. Uncertainty: up to in. Major dia.: 0.05 up to 6 in. Uncertainty: up to in. Pitch dia.: 0.05 up to 6 in. Uncertainty: up to in. Flank angle: 30 deg. of arc Uncertainty: 4 up to 20 min. of arc To clean the TI, 1 gallon container Range: 0.05 up to 6 in. Uncertainty: up to in. Type: GO NOT GO, diameters same as TI minimum/maximum minor diameter, respectively Range: 0 to 12 in. Uncertainty: in. Range: 0 to in. Uncertainty: in. Range: 0 to 12 in. Uncertainty: NA Size: as required to hold item 2.1 during effective minor diameter test Size: 24 x 36 in., min. Grade: A To seal the TI after adjustment For cleaning and polishing a TI Protractor range: 0 to 90 deg. Uncertainty: 1 min. Micrometer range: 0 to 1 in. Uncertainty: in. To hold TI cast in place on the optical comparator To prepare a cast of TI internal threads Calibration Equipment Supplied with TI; or Local supply Local supply Local supply Brown and Sharpe Federal Products 230P201 Federal Products 2400; or Starrett or Taft Pierce 9128, , 9132, 9133 and 9134 Rahn Granite Surface Plate Co. 3624; or Collins Microflat Co GSA ; or Local supply Local supply Jones and Lamson Machine Co. PC 14A Permoplast Modeling Clay No. X30; or American Art Clay Co. GSA ; or Local supply 3

7 Item 2.14 Potassium dichromate solution 2.15 Protective coating 2.16 Gages and gaging for unified inch screw threads 2.17 Screw thread standards for Federal services Minimum Use Specifications Mixture of potassium dichromate crystals and water, in a proportion of 1.5 oz crystals to 1 qt. of water To protect TI threads and body from rust and corrosion Reference data Reference data Local supply Calibration Equipment DIP PAK ; SEAL PEAL ; or Local supply ANSI/ASME B FED STD H28 SECTION 3 PRELIMINARY OPERATIONS 3.1 If applicable, remove the protective coating (item 2.16) from the TI. Wash the TI with Stoddard Solvent (item 2.2). Blow the TI dry with clean, dry air, as required. 3.2 Ensure that the TI is clean and free from foreign matter, defects or damage which would impair its serviceability. 3.3 Examine the TI thread flanks for evidence of rust of corrosion, nicks or burrs. Remove rust and/or burrs by applying an Arkansas stone (item 2.10). Reject the TI if rust or corrosion is too severe or extensive to be removed, and/or if the corrosion or nicks would interfere with proper mating of the TI with external threads in normal use. 3.4 Place the TI on a work table or surface plate (item 2.8); allow a minimum of two hours for temperature stabilization before proceeding. 3.5 Ensure that the temperature in the calibration area is maintained within 4 F of the reference temperature, 68 F, with temperature changes limited to 2 F/hour. The humidity should be controlled so as not to exceed 45% RH. Calibration area temperatures as high as 76 F can be tolerated if the TI is allowed to stabilize to a temperature within 2 F of the measurement device and gage blocks used to zero the measurement device. 4

8 3.6 Inspect the TI to determine and record the nominal size, threads per inch (TPI), series designation (UN, UNC, UNF, etc.), class (1A, 2A, 3A), type (GO, NOT GO, LO thread ring gage) and the actual tolerances to be used for lead, pitch and minor diameter, flank angle and root clearance, based on the applicable tolerances listed for the TI in ANSI/ASME B (item 2.16) or FED STD H28 (item 2.17) or other document, as specified. Prepare a checklist for the TI, as necessary, following the checklist examples in this procedure. S TI marking/labeling varies with the manufacturer/user activity practice. Consult ANSI/ASME B , FED STD H28 and/or the user activity for additional information, as necessary, to completely identify the TI and applicable tolerances before proceeding. This procedure addresses 60 form thread ring gages which are not tapered. The basic methods of measuring pitch and minor diameter are not fully applicable to taper pipe thread ring gages (American Standard NPT pipe threads). Refer to NAVAIR 17 20MD 149L for instructions on the calibration of taper pipe thread ring gages. The general practice is to interpret the above tolerances as absolute values. For example, a minor diameter tolerance of to should be interpreted as to NAVAIR 17 20MD Connect the optical comparator (item 2.11) to an appropriate power source, and set the power switch to on. SECTION 4 CALIBRATION PROCESS Unless otherwise specified, verify the results of each test and take corrective action whenever the test requirement is not met, before proceeding. 4.1 THREAD RING GAGE TESTS The TI calibration is based on fitting the TI to a thread setting plug of the same nominal size. Generally, master plugs and rings are maintained by the calibrating activity. The master thread setting plug shall be constructed to the tolerances specified in FED STD H28, Section 6, or ANSI/ASME B , as applicable. If the TI is constructed in accordance with the specifications of another document than the above, the thread setting plug must also meet the specifications of that document. 5

9 4.1.1 Lead and Pitch Diameter Select the appropriate thread setting plug (item 2.1) per paragraph 3.6 requirements, and clean as required Apply a light lubricant (instrument oil) on the flanks of the thread setting plug. The fit method relies on the accuracy of the critical parameters of the thread setting plug. Whenever possible, it is suggested that the thread setting plug be calibrated per NAVAIR 17 20MD 141L just before calibrating the TI Screw the TI onto the truncated portion of the thread setting plug. Verify that a satisfactory fit is obtained Screw the TI across the full length of the full form portion of the thread setting plug. Verify that there is only a slight or no change of fit. Record the result on the checklist. A satisfactory fit on both the truncated and full form portions of the plug indicates that the TI lead and pitch diameters are, to a high degree of probability, within the tolerance limits listed. CAUTION DO NOT FORCE THE TI ONTO THE FULL FORM PORTION OF THE THREAD SETTING PLUG GAGE IF ANY RESTRICTION TO TURNING IS D, AS DAMAGE TO THE THREAD CREST OF THE SETTING PLUG WILL OCCUR. If the TI ring is non adjustable, and a satisfactory fit is not obtained, proceed directly to step If step cannot be satisfactorily performed on an adjustable ring, perform the following steps: Remove the sealing compound (item 2.9) from the TI locking screw holes, and loosen the locking screws Enlarge the TI by turning the adjustment screw clockwise approximately 1.8 turn; make the TI smaller by turning the screw counterclockwise. The amount of screw adjustment required depends on the amount the TI is out of tolerance. Adjustment of the TI major/pitch diameters may also affect TI roundness Secure the handle of the thread setting plug in a vise, or clamp to a stationary table, so that the thread element is cleared to accept the TI. 6

10 Screw the TI onto the truncated portion of the thread setting plug Alternately adjust the adjusting screw and tighten the locking screw until a light drag fit is obtained when the TI is screwed on the thread setting plug truncated portion. Using two screwdrivers will simplify setting of the thread ring gage Lightly tap the knurled portion and sides of the TI with a soft tipped hammer to set the threads of the thread ring to the truncated form of the thread setting plug Perform steps and as often as required After satisfactory adjustment has been obtained, screw the TI across the full length of the full form portion of the thread setting plug. Verify that there is only a slight or no change of fit. Record the result on the checklist If step cannot be performed satisfactorily, perform the following steps: Loosen the locking screw, and enlarge the TI until a free fit on the full form portion of the setting plug is obtained Perform steps through on the full form portion of the thread setting plug Perform paragraph to verify TI concentricity after adjusting the TI Screw the TI onto the truncated portion of the thread setting plug. If the TI (adjustable or non adjustable ring) goes on only approximately halfway, the flanks may be worn. Perform paragraph if the TI is to be salvaged if not, reject the TI Check for shake. Shake indicates that the TI major diameter is not cleared and/or the flanks are excessively worn the TI should be rejected Screw the TI onto the full form portion of thread setting plug. If the TI goes only approximately halfway, the flanks may be worn Perform paragraph if the TI is to be salvaged if not, reject the TI Remove the TI from the thread setting plug. Apply sealing compound to the TI locking screw holes Minor Diameter Select the appropriate GO NOT GO cylindrical plain plug(s) (item 2.11) required to test the TI minor diameter, as determined in paragraph 3.6. The calibration of the minor diameter cannot be performed without the appropriate plain plug(s). However, it is possible to perform a special calibration which excludes the minor diameter. It is also possible to measure the minor diameter with an appropriate bore gage (or Intrimik), provided that the test accuracy ratio (T.A.R.) is 3:1 or greater. 7

11 Verify that the GO end of the plain plug passes through the TI ring Verify that the NOT GO end of the plain plug will not pass through the TI ring Effective Minor Diameter S This test is not required if a satisfactory fit was obtained between the TI and the truncated and full form portions of the thread setting plug. This test should not be performed on an adjustable TI until the TI has been adjusted one or more times, and the fit test of paragraph has been performed to verify a satisfactory fit. This test verifies that the concentricity of the TI pitch diameter to the minor diameter is satisfactory. The test seldom needs to be performed if a satisfactory fit cannot be obtained between the TI and corresponding thread setting plug as such a TI is generally rejected. The test is not recommended for a TI with a major diameter of less than 3/8 inch due to the difficulty of obtaining accurate measurements on very small diameters Set up the equipment as shown in Figure 1, except do not screw the TI onto the thread setting plug at this time. TI Figure 1. Thread Ring Gage Effective Minor Diameter Test Configuration A stack of wrung gage blocks may be used if a gage block column type height indicator (item 2.4) is not available. 8

12 Set the electronic height indicator (item 2.5) amplifier to a range which has minor divisions of to inch. Generally, best results will be obtained by making preliminary measurements on a less sensitive range to facilitate the attainment of on scale indications, and to avoid large fluctuations of the pointer while searching for a maximum or minimum indication. The sensitivity should be increased to improve the accuracy of the final indication, as necessary. NAVAIR 17 20MD Select a 60 thread measuring wire of the correct best wire diameter required for the thread setting plug threads per inch (TPI) Position the thread measuring wire in a horizontal, balanced position between the first and second thread setting plug threads. Scotch tape can be used to hold the wire in place on the thread setting plug of a small diameter. The tape must not interfere with the measurement contact area or be allowed to tilt the wire from the horizontal Position the height gage (item 2.6) so that the gage head stylus tip contacts the top of the thread measuring wire, as evidenced by an on scale amplifier meter indication Sweep the stylus tip approximately 1/8 inch along the length of the thread measuring wire to obtain a maximum meter indication, being careful not to tilt the wire from its horizontal balance Adjust the amplifier ZERO/ZEROING control for an exact zero meter indication Reposition the thread measuring wire in a horizontal, balanced position between the last two thread setting plug threads Perform steps and Note the indication of the amplifier meter Ensure that the difference between zero and the indications of step is equal to or less than inch, the thread setting plug parallelism to the surface plate (item 2.8). S A difference of less than inch ensures that the threads and centerline of the thread setting plug are sufficiently parallel to the reference surface of the surface plate, and that out of parallelism will not significantly affect the reference height value A at the top of the thread measuring wire with respect to reference height B along the thread setting plug and TI centerlines. Ensure that the thread setting plug and TI do not move relative to the surface plate. Two vee block clamps should be used to lock the thread setting plug handle in place; if necessary, clamp the vee block (item 2.7) to the surface plate. 9

13 If the difference value of step exceeds inch, place (shim(s) under the appropriate end of the vee block. Perform steps through and add/remove shim(s) as necessary until a difference value of inch or less is achieved Ensure that the amplifier has been zeroed at the top of the thread measuring wire Position the height gage so that the gage head stylus tip lies above the nearest gage block of the gage block height indicator placed nearby on the surface plate Adjust the gage block height indicator micrometer to contact the gage head stylus, and continue the adjustment to obtain an amplifier meter indication of zero Record the reference height A, as read from the height indicator micrometer, on the checklist, to the nearest inch Calculate the reference height B of the thread setting plug centerline from the following equation and record the result: B A C E 2 where B Thread setting plug centerline height, nearest in. A Reference height A, step , nearest in. C Best size wire constant for thread setting plug, nearest in., ANSI/ASME B E Pitch diameter of thread setting plug, nearest in., from the Report of Calibration or current calibration value Move the height gage and stylus to one side. Screw the TI onto the truncated section of the thread setting plug, leaving one full TI thread exposed Position the height gage so that the gage head stylus tip contacts the top of the exposed TI thread, at the very bottom of the ring Traverse the bottom of the TI ring thread crest until a minimum repeatable indication is obtained on the amplifier meter. Do not move the height gage until the next step is completed Rotate the TI slowly 360 or slightly more in the direction which exposes another TI thread, noting the point of maximum indication on the meter. Rotate the TI back and forth as necessary to obtain the maximum indication possible Adjust the amplifier ZERO/ZEROING control for an exact meter indication Position the height gage so that the gage head stylus tip lies above the nearest gage block of the gage block height indicator placed nearby Adjust the gage block height indicator micrometer to contact the gage head stylus, and continue the adjustment to obtain an amplifier meter indication of zero. 10

14 Record the reference height D, representing the highest position of the TI minor diameter during the rotation, to the nearest inch Subtract value D (step ) from value B (step ). Multiply the resulting value by 2 to obtain the actual measured TI minor diameter Referring to the appropriate table in ANSI/ASME B or FED STD H28, calculate the TI minimum E.M.D. (effective minor diameter) as follows: For the GO thread ring gage, subtract the sum of the gage tolerances for the pitch and minor diameters from the minimum minor diameter listed. Record on the checklist. NAVAIR 17 20MD 143 As an example of the calculation, the minimum E.M.D. for a 3 1/2 12 UN 3A GO thread ring gage is: Minimum minor dia., in., pitch dia. tol., , minor dia. tol., Therefore, the minimum E.M.D ( ) in For the LO thread ring gage, subtract twice the sum of the gage tolerances for the pitch and minor diameters from the minimum minor diameter listed. Record on the checklist. As an example of the calculation, the minimum E.M.D. for a 3 1/2 12 UN 3A NOT GO thread ring gage is: Minimum minor dia., in., pitch dia. tol., , minor dia. tol., Therefore, the minimum E.M.D ( ) in Ensure that the calculated TI minimum E.M.D., FRONT, is equal to or less than the actual measured value (step ). Allowance should be made for measurement error. For example, if the actual measured value is in. less than the minimum E.M.D., the result could be attributed to measurement error. If the minimum E.M.D. is in. (or a larger value) more than the actual measured value, the entire measurement should be repeated to ensure that the results are valid before declaring the TI to be out of tolerance Unscrew the TI from the thread setting plug, being careful not to disturb the test setup Rotate the TI end for end (180 ) so that the other face of the TI faces the thread setting plug. Screw the TI onto the truncated section of the plug, leaving one full TI thread exposed Perform steps through , but for the TI minimum E.M.D., BACK. Disconnect the test setup. 11

15 4.1.4 Flank Angle A flank angle test is not required if the tests described in paragraphs through provide satisfactory results, as such results infer that the TI flank angle is satisfactory to a high degree of probability. If the above is true, proceed directly to step to terminate the calibration. However, if one or more of the above tests provided out of tolerance results, and the TI diameter could not be adjusted to within tolerance, the flank angle can be tested by making a cast of the TI threads. The cast is then measured much the same as if it were a plug. If the flank angle of the cast is within the TI tolerance, it should be possible to salvage the TI through reworking/regrinding by personnel knowledgeable in such operations. If the flank angle is out of tolerance, or the TI salvage is not required, the TI must be rejected. It should also be noted that repeated measurements of the flank angle during each TI calibration are not normally required Ensure that the TI has been inspected and cleaned, as necessary, per paragraphs 3.1 through Using the modeling clay (item 2.12), prepare a mold across the width of the TI, between the slots. The mold should be approximately 3/4 inch in width Prepare a casting mixture of the dental plaster (item 2.13) and the potassium dichromate solution (item 2.14), following the instructions on the container or in FED STD H28. CAUTION TAP WATER WILL STAIN THE TI THREADS IF MIXED WITH THE DENTAL PLASTER WHEN PREPARING THE CAST Pour the mixture into the mold. Ensure that the mixture is deep enough to give strength to the cast. In most instances, the mixture will be approximately 3/8 to 1/2 inch thick. If a handle is desired on the cast, place a paper clip or small screw, e.g., 6 32, etc., in the mold so that the mixture can form around it Allow the mixture to harden, and remove the cast from the TI. To remove the cast from the TI, it is permissible to tap the side of the ring gage with a soft tipped hammer. The resulting vibrations will dislodge the cast from the threads Place the cast on an optical comparator. Use modeling clay to hold the cast in place. Set the screen to Support the TI cast, as necessary. 12

16 Position the cast to align the minor diameter parallel with the screen cross line, and so that the opposite flanks are in focus at the same focal point. NAVAIR 17 20MD 143 If the cast image is fuzzy, lightly brush the threads of the cast with a camel s hair brush to remove particles. Brush in one direction only Calibrate the TI flank angle as described in NAVAIR 17 20MD 141L, testing the TI cast as if it were a thread plug gage. If properly made, the cast of a thread ring gage is very similar to a thread plug gage. However, it is not possible to measure the major and pitch diameter of a cast to the same accuracy as when measuring a thread plug gage because of the difference in the material Root Clearance A root clearance test is not required if the tests described in paragraphs through provide satisfactory results, as such results infer that the TI root clearance is satisfactory to a high degree of probability. If the above is true, proceed directly to step to terminate the calibration. However, if one or more of the above tests provided out of tolerance results, and the TI diameter could not be adjusted to within tolerance, the root clearance can be tested by making a cast of the TI threads. Generally, the flank angle of the TI cast would be tested before testing the root clearance. It should also be noted that repeated measurements of the root clearance during each TI calibration are not normally required Ensure that the TI cast is properly mounted on the optical comparator. Modeling clay or tape can be used to hold the cast in the correct position Calibrate the TI root clearance as described in NAVAIR 17 20MD 141L, testing the TI cast as if it were a thread plug gage Inspect the TI; remove any cast material from the TI threads, as necessary If no other measurements are to be performed, set all applicable power switches to off, and secure the equipment If a protective coating was removed from the TI in paragraph 3.1, and/or it is required to protect the TI threads, apply a similar coating to the TI, following standard practice, ( 14 blank) 13

17 CALIBRATION CHECKLIST TEST INST (S) National Twist Drill 1/2 13 UNC 3A GO NO GO Thread Ring Gage PROC. NO. PROCEDURE STEP NO. (1) NA 17 20MD 143 FUNCTION TESTED (2) MFG. MODEL SER. NO. NOMINAL (3) MEASURED VALUES FIRST RUN SECOND RUN (4) (5) OUT OF TOL (6) CALIBRATION TOLERANCES (7) 3.2/3.3 TI inspection ck ( ) NA (size) (TPI) (series) 3.6 TI data UNF NA (class) (type) (tol.) 3A HI, LO X NA 4.1 Thread Ring Gage Tests Lead and Pitch Diameter Select setting plugs ck ( ) NA GO end (in.) Fits truncated portion to Fits full form portion NOT GO end (in.) Fits truncated portion to Fits full form portion Minor diameter GO end (in.) GO plug passes to NOT GO plug does not pass NO GO end (in.) GO plug passes to NOT GO plug does not pass Effective minor diameter Setting plug parallelism ck ( ) NA within in. FRONT (in.) (in.) Reference height A NA B NA D NA TI minor diameter NA TI min. E.M.D., FRONT NA measured value Page 1 of 2 15

18 CALIBRATION CHECKLIST TEST INST (S) National Twist Drill 1/2 13 UNC 3A GO NO GO Thread Ring Gage PROC. NO. PROCEDURE STEP NO. (1) NA 17 20MD 143 FUNCTION TESTED (2) MFG. MODEL SER. NO. NOMINAL (3) MEASURED VALUES FIRST RUN SECOND RUN (4) (5) OUT OF TOL (6) CALIBRATION TOLERANCES (7) BACK (in.) (in.) Reference height D NA TI minor diameter NA TI min. E.M.D., BACK NA measured value Flank angle / Prepare TI cast ck ( ) NA Flank angle (, min.) (, min.) (degrees, minutes) Leading flank to Trailing flank Root Clearance (in.) (in.) (in.) Straight V, GO min. NOT GO min. 16 Page 2 of 2

19 APPENDIX A REPRESENTATIVE TEST INSTRUMENTS TIs which may be calibrated using this procedure include, but are not limited to, the following: MODEL/SERIES MANUFACTURER NOMENCLATURE TOLERANCE FD Lockheed Corp. Thread Ring Gage X UNC J & L Industsries Thread Ring Gage X Master Gage Co. Thread Ring Gage X Regal Beloit Corp. Thread Ring Gage X Sheffield Measurement Thread Ring Gage X Div. Size Control Co. Thread Ring Gage X Southern Gage Co. Thread Ring Gage X Van Keuren Thread Ring Gage X UNF Greenfield Div., TRW Thread Ring Gage X Master Gage Co. Thread Ring Gage X Regal Beloit Corp. Thread Ring Gage X Southern Gage Co. Thread Ring Gage X Widell Industries Thread Ring Gage X UNJF Southern Gage Co. Thread Ring Gage X UNS Regal Beloit Corp. Thread Ring Gage X UNJF 3A Johnson Gage Co. Thread Ring Segment Gage X UNJF 3A Southern Gage Co. Thread Ring Gage X UNS 2A Johnson Gage Co. Thread Ring Gage X 1 14UNS 3A GO NO GO National Twist Drill Thread Ring Gage X 1/2 13 UNC 3A GO NO GO Thread Ring Gage X 1/4 20 UNC 3A GO NO GO Regal Beloit Corp. Thread Ring Gage Set X 1/4 28 UNF 3A GO NO GO National Twist Drill Thread Ring Gage X UNF 2A Widell Industries Thread Ring Gage X 7/16 20UNF 3A GO NO GO Regal Beloit Corp. Thread Ring Gage Set X A 1