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)

width of the thread ridge and the thread groove equal. Pitch Line. The pitch line is linear and parallel to the center line of the pitch cylinder. De-fined where thread ridge and thread groove are equal along the length of the thread. Thread Axis. The thread axis is the axis of its pitch cylinder. Actual Size. An actual size is a measured size ...

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