THREAD GAGING REFERENCE GUIDE

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Know your threads, L. S. STARRETT COMPANY121 Crescent Street Athol, MA 01331Telephone (508) 249-3551Fax (508) 249-8495Table of ContentsSECTION 1:Fundamentals of Screw THREAD Technology ................. 4 - 7SECTION 2:Definitions and Terminology ........................................ .. 8 - 11SECTION 3:Gage Design Contacts ........................................ .......... 12 - 13SECTION 4:Technical Considerations ........................................ ...... 14 - 23SECTION 5:Plating, Metric and RFQ ........................................ ....... 24 - 274Screw THREAD DesignationScrew THREAD DesignationScrew THREAD DesignationScrew THREAD DesignationScrew THREAD DesignationEXAMPLE: .3125 - 24 UNJF - 3A (B).3125 = Nominal Diameter = Maximum Major Diameter24= Number of threads per inchUN= Unified National (60 V- THREAD )J= Controlled root radius High Strength(Minor diameter increased from UN to UNJ.)F= Fine THREAD series3= THREAD classA= External threadB= Internal threadScrew THREAD AssemblyFUNDAMENTALS OF SCREW THREAD TECHNOLOGY5SECTION 1Functional Diameter SizeWidth of THREAD Ridge = Width of THREAD GroovePitch Diameter Size + Variations of THREAD Elements and Characteristics = Functional Diameter SizePitch Diameter SizeThe Functional diametersize is the Pitch diam-eter size plus the cumu-lative effect of variationsin lead, (including unifor-mity of helix) flankangle, taper, and rou

Screw Thread Gaging Systems for Dimensional Acceptability – Inch and Metric Threads (UN, UNR, UNJ, M and MJ). Distributed by: Gage Crib Worldwide Inc 6701 Old 28th St SE, Suite B Grand Rapids, MI 49546-6937 USA Phone: 001.616.954.6581 Web: www.gagecrib.com

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