Microscope Objective Threads Machinery's Handbook, 31st Edition
2117
_p_ 20 __ p
The dotted line indicates the full form British Whitworth Thread on which the Royal Microscopical Society thread is based Internal Thread (Nut) 1/2 Major Diameter Allowance on External Thread 1/2 Major Diameter Tolerance on External Thread
Fc
U
1/2 PD Tolerance on External Thread 1/2 Tolerance (External Thread Only) 1/2 PD Tolerance on External Thread
55
1/2 Minor Diameter Tolerance on Internal Thread
Fc
U
Fr
External Thread (Screw)
12 __ p
Permissible form of thread from new tool
Tolerances, Allowances and Crest Clearances for Microscope Objective Thread (AMO) ANSI/ASME B1.11-1958 (R2016) Table 1. Definitions, Formulas, Basic and Design Dimensions ANSI/ASME B1.11-1958 (R2016) Symbol Property Formula Dimension Basic Thread Form α Half angle of thread … 27 ° 30´ 2 α Included angle of thread … 55 ° 00´ n Number of threads per inch … 36 p Pitch 1/ n 0.027778 H Height of fundamental triangle 0.960491 p 0.026680 h b Height of basic thread 0.640327 p 0.0178 r Radius at crest and root of British Standard Whitworth basic thread (not used) 0.137329 p 0.0038
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