Transcription of THREAD MEASURING WIRE FORMULAS
1 THREAD MEASURING wire FORMULAS . Best Size Wires Approximate FORMULAS for Measured Pitch Diameter * Wires which touch the THREAD at the pitch diameter are known as The following approximate FORMULAS for computing the pitch diameter, from the Best Size Wires. Such wires are used because the measurements of measurement over wires, should be used only for screws having lead angles from pitch diameter are least affected by errors that may be present in the 0 to 5 . These FORMULAS neglect the effect of lead angle and give results which angle of the THREAD . The diameter of the MEASURING wires is represented show the screw to be larger than the true condition.
2 The FORMULAS are for any wire by the letter G. size which will fit in the THREAD . The approximate formula for Included THREAD formula for Finding Pitch Diameter G = secant a Designation Best Size Wires is: 2n Angle Depth With 3 wire Method .649519 E = M - (3G - .86603). For 60 threads Best Size Wires G = .57735 or .57735p Unified & National 60 . n n n USA Standard Taper .8 E = - ( - .86603). 60 . For 55 threads Best Size Wires G = .56369 or .56369p Pipe (3 wires) n n n .8660254 E = M - (3G - .86603). Sharp V 60 . n n For 53 - 8 threads Best Size Wires G = .55902p .649519 E = M - (3G - .86603). International Metric 60.
3 N n For 47 1/2 threads Best Size Wires G = .54626p .64033 E = M - ( - .96049). Whitworth 55 . n n For 40 threads Best Size Wires G = .53208 or .532089p British Association 47 1/2 .6p E = M - ( - ). n For 29 threads Best Size Wires G = .51645 or .51645p Lowenherz 53 - 8 .75p E = M - ( - p). n 1 E = M - ( - ). Acme Screws 29 . 2n n Unsymmetrical Threads Acme Taps 29 . 1 E = M - ( - ). 2n n 1 a + a2 a -a .6866 Use wire .5149 to come flush with top of THREAD E=M+ -G (1 + cosec 1 cos 1 2 ) 29 Worm 29 n n n (tan a1 + tan a 2) 2 2..6866 Use wire .51234 to come flush with top of THREAD 40 Worm 40 n n a + a 2) sec a G = tan ( 1 1 Where a1 = Large Angle 2 a = Small Angle 2.
4 Approximate FORMULAS for Basic Measurement Over Wires n (tan a1 + tan a 2) When cutting or grinding a screw THREAD , it is desirable to know what the measurement over wires would be for a screw of the theoretical basic size. The following approximate FORMULAS are the same as those above, but transposed and referred to the basic outside diameter of the screw . The same qualifications apply. For Modified Buttress 45 and 7 G = .54147. n Included formula for Finding Measurement Designation Angle Over Wires On 29 and 40 worm threads, the addendum above the pitch diameter is .3183. Unified & National 60 M = D - + 3G.
5 N n The THREAD depth of .6866. provides a clearance of .50. at the bottom of the THREAD . E - .8660254 + n n American Standard M= n 60 . Pipe Sharp V. 2. 60 M = D - + 3G. Symbols for Basic Dimensions and wire Measurement n Major Diameter = D Width or basic flat at top, International Metric 60 M = D - + 3G. Corresponding Radius = d crest or root = F. Pitch Diameter = E Depth of Basic truncation = f Whitworth 55 M = D - + Depth of Sharp V THREAD = H n Corresponding Radius = e Minor Diameter = K Depth of American Nation or unified British Association 47 1/2 M = D - + Corresponding Radius = k THREAD form = h Angle of THREAD = A Length of engagement = Q Lowenherz 53 - 8 M = D - + One half angle of THREAD = a Included angle of taper = Y.
6 One half included angle of taper = y Acme Screws, Taps M = D - + G. Number of turns per inch = N 29 n and 29 Worms Number of threads per inch = n Measurement over wires MOW = M. wire Diameter = G 29 Worm 29 M = D (with .5149 wires). Lead L = 1/N n pitch p = 1/n Corresponding radius = g M = D (with .51234 wires). Helix Angle = s n 40 Worm 40 Also Tangent of helix angle M=D- + S = n 30 THREAD Check Product Catalog | Toll-Free: Phone 1-800-767-7633 | Fax 1-800-767-2034.
