ASME Y14.6:2001 pdf free download – SCREW THREAD REPRESENTATION
3.2 Thread Specification
In the U.S. the name and number of the controllingthread standard is frequently omitted from the drawing.Reference is made instead to the designation symbolsof the standard,such as series symbols and classsymbols.To avoid misundcrstanding, it is recommendedthat the controlling organization and thread standardbe specified or otherwise referenced on the drawing.Examples follow:
3.2.1 On drawings with threaded parts.for standardserics screw threads,the designation of the screw threadis noted and optionally supplemented by the pitchdiameter and its tolerance,or pitch diameter limits.
3.2.1.1 For 60 deg inch threads, the thread designa-tion should include,in sequence, the norminal diameterin inches,the number of threads per inch,the lettersymbol of the thread series,the number and letter ofthe thread class,and any qualifying information. Formultiple start thrcads，replace the number of threadsper inch with pitch in inches (P),lead in inches (L),and the number of starts in parentheses. An alternatedesignation method for multiple start threads retainsthe number of threads (pitches) per inch and adds leadin inches (L)and number of starts inparenthesesfollowing it.
For 60deg mctric threads，the thread designationshould include in sequence.the mctric thread/formidentifier (M or MJ), the nominal diameter in millime-ters,a lowercase“x,”the pitch in millimeters [or formultiple start threads,L (lead in millimeters),P (pitchin millimcters), and number of starts in parentheses],pitch diameter tolerance symbol, crest diameter tolerancesymbol (if different from that of the pitch diameter).and any qualifying information.
The thread length,the hole size， and the chamferor countersink may be included in the note or dimen-sioned on the drawing of the part. Thread gaging systemmay be added to the thread designation in parentheses,or otherwise included in a drawing note. Acceptabilityof screw threads shown on a drawing shall be inaccordance with the designated system,in accordancewith ASME B1.3M.
3.2.1.2 In general practice, the general designationand any diameter limits are in note form and referredto the drawing of the thread with a leader line. Figures15 through 17 illustrate and explain the elements ofdesignation of screw threads.
NOTES (for metric thread designations):
a) When transmitting a thread designation，where only capitallettcrs are available, the extenal or intcrnal thread may need furtheridentification.Thus, the tolerance class identification is followed bythe abbreviations EXT or INT in capital letters (e.g.. M6X1-4G6GEXT or M6X1-6H INT).
(b) When indicating fitbetween threads，specify in the threaddesignation,the internal and extermal thread classes separated by aslash (e-g,MJ6x1-4HSH4h6h).
(c) Where the pitch and crest diameter tolerance symbols areidentical,the symbol need only be given once (e.g.M20x2.5-6H, with “6H””representing the pitch and minor diamctertolerance class symbols).