美制UN系列螺纹标准

U N IF IE D S CR EW T H RE A D S 17 35 Fo r U N R th re ad fo rm su bs tit ut e U N R fo r U N fo r e xt er na l t hr ea ds on ly . Ta bl e 2 . D ia m et er -P itc h C om bi na tio ns fo r S ta nd ar d Se ri es of T hr ea ds (U N/ UN R) Si ze sa N o. o r In ch es a Si ze s s ho w n in p ar en th es es ar e s ec on da ry si ze s. Pr im ar y siz es o f 4 1 ⁄ 4 , 4 1 ⁄ 2 , 4 3 ⁄ 4 , 5 , 5 1 ⁄ 4 , 5 1 ⁄ 2 , 5 3 ⁄ 4 an d 6 in ch es al so ar e i n th e 4 , 6 , 8 , 1 2, an d 16 th re ad se rie s; se co nd ar y siz es o f 4 1 ⁄ 8 , 4 3 ⁄ 8 , 4 5 ⁄ 8 , 4 7 ⁄ 8 , 5 1 ⁄ 8 , 5 3 ⁄ 8 , 5 5 ⁄ 8 , an d 5 7 ⁄ 8 al so ar e i n th e 4 , 6 , 8 , 1 2, an d 1 6 t hr ea d s er ie s. B as ic M ajo r D ia . In ch es Th re ad s p er In ch Se rie s w ith G ra de d Pi tc he s Se rie s w ith U ni fo rm (C on sta nt) Pi tch es Co ar se U N C Fi ne b U N F b F o r di am et er s o v er 1 1 ⁄ 2 in ch es , u se 1 2- th re ad se rie s. Ex tra fi n ec U N EF c Fo r di am et er s o v er 1 11 ⁄ 16 in ch es , u se 1 6- th re ad se rie s. 4- U N 6- U N 8- U N 12 -U N 16 -U N 20 -U N 28 -U N 32 -U N 0 0. 06 00 … 80 Se rie s d es ig na tio n sh ow n in di ca te s t he U N th re ad fo rm ; h ow ev er , th e U N R th re ad fo rm m ay b e sp ec ifi ed b y su bs tit ut in g U N R in p la ce o f U N in a ll de sig n at io ns fo r e x te rn al th re ad s. (1) 0. 07 30 64 72 2 0. 08 60 56 64 (3) 0. 09 90 48 56 4 0. 11 20 40 48 5 0. 12 50 40 44 … … … … … … … … … 6 0. 13 80 32 40 … … … … … … … … U N C 8 0. 16 40 32 36 … … … … … … … … U N C 10 0. 19 00 24 32 … … … … … … … … U N F (12 ) 0. 21 60 24 28 32 … … … … … … U N F U N EF 1 ⁄ 4 0. 25 00 20 28 32 … … … … … U N C U N F U N EF 5 ⁄ 1 6 0. 31 25 18 24 32 … … … … … 20 28 U N EF 3 ⁄ 8 0. 37 50 16 24 32 … … … … U N C 20 28 U N EF 7 ⁄ 1 6 0. 43 75 14 20 28 … … … … 16 U N F U N EF 32 1 ⁄ 2 0. 50 00 13 20 28 … … … … 16 U N F U N EF 32 9 ⁄ 1 6 0. 56 25 12 18 24 … … … U N C 16 20 28 32 5 ⁄ 8 0. 62 50 11 18 24 … … … 12 16 20 28 32 (11 ⁄ 16 ) 0. 68 75 … … 24 … … … 12 16 20 28 32 3 ⁄ 4 0. 75 00 10 16 20 … … … 12 U N F U N EF 28 32 (13 ⁄ 16 ) 0. 81 25 … … 20 … … … 12 16 U N EF 28 32 7 ⁄ 8 0. 87 50 9 14 20 … … … 12 16 U N EF 28 32 (15 ⁄ 16 ) 0. 93 75 … … 20 … … … 12 16 U N EF 28 32 1 1. 00 00 8 12 20 … … U N C U N F 16 U N EF 28 32 (1 1 ⁄ 1 6) 1. 06 25 … … 18 … … 8 12 16 20 28 … 1 1 ⁄ 8 1. 12 50 7 12 18 … … 8 U N F 16 20 28 … (1 3 ⁄ 1 6) 1. 18 75 … … 18 … … 8 12 16 20 28 … 1 1 ⁄ 4 1. 25 00 7 12 18 … … 8 U N F 16 20 28 … 1 5 ⁄ 1 6 1. 31 25 … … 18 … … 8 12 16 20 28 … 1 3 ⁄ 8 1. 37 50 6 12 18 … U N C 8 U N F 16 20 28 … (1 7 ⁄ 1 6) 1. 43 75 … … 18 … 6 8 12 16 20 28 … 1 1 ⁄ 2 1. 50 00 6 12 18 … U N C 8 U N F 16 20 28 … (1 9 ⁄ 1 6) 1. 56 25 … … 18 … 6 8 12 16 20 … … 1 5 ⁄ 8 1. 62 50 … … 18 … 6 8 12 16 20 … … (1 11 ⁄ 16 ) 1. 68 75 … … 18 … 6 8 12 16 20 … … 1 3 ⁄ 4 1. 75 00 5 … … … 6 8 12 16 20 … … (1 13 ⁄ 16 ) 1. 81 25 … … … … 6 8 12 16 20 … … 1 7 ⁄ 8 1. 87 50 … … … … 6 8 12 16 20 … … (1 15 ⁄ 16 ) 1. 93 75 … … … … 6 8 12 16 20 … … 2 2. 00 00 41 ⁄ 2 … … … 6 8 12 16 20 … … (2 1 ⁄ 8 ) 2. 12 50 … … … … 6 8 12 16 20 … … 2 1 ⁄ 4 2. 25 00 4 1 ⁄ 2 … … … 6 8 12 16 20 … … (2 3 ⁄ 8 ) 2. 37 50 … … … … 6 8 12 16 20 … … 2 1 ⁄ 2 2. 50 00 4 … … U N C 6 8 12 16 20 … … (2 5 ⁄ 8 ) 2. 62 50 … … … 4 6 8 12 16 20 … … 2 3 ⁄ 4 2. 75 00 4 … … U N C 6 8 12 16 20 … … (2 7 ⁄ 8 ) 2. 87 50 … … … 4 6 8 12 16 20 … … 3 3. 00 00 4 … … U N C 6 8 12 16 20 … … (3 1 ⁄ 8 ) 3. 12 50 … … … 4 6 8 12 16 … … … 3 1 ⁄ 4 3. 25 00 4 … … U N C 6 8 12 16 … … … (3 3 ⁄ 8 ) 3. 37 50 … … … 4 6 8 12 16 … … … 3 1 ⁄ 2 3. 50 00 4 … … U N C 6 8 12 16 … … … (3 5 ⁄ 8 ) 3. 62 50 … … … 4 6 8 12 16 … … … 3 3 ⁄ 4 3. 75 00 4 … … U N C 6 8 12 16 … … … (3 7 ⁄ 8 ) 3. 87 50 … … … 4 6 8 12 16 … … … 4 4. 00 00 4 … … U N C 6 8 12 16 … … … M ac hi ne ry 's H an db oo k 27 th E di ti on C op yr ig ht 2 00 4, I nd us tr ia l P re ss , I nc ., N ew Y or k, N Y UNIFIED SCREW THREADS1736 Ta bl e 3 . S ta nd ar d Se ri es an d Se le ct ed C om bi na tio ns — U ni fie d Sc re w T hr ea ds N om in al S iz e, Th re ad s p er In ch , an d Se rie s D es ig na tio na Ex te rn al b In te rn al b Cl as s A llo w - an ce M ajo r D iam ete r Pi tc h D ia m et er U N R M in or D ia .,c M ax (R ef. ) Cl as s M in or D ia m et er Pi tc h D ia m et er M ajo r D ia m et er M ax d M in M in e M ax d M in M in M ax M in M ax M in 0– 80 U N F 2A 0. 00 05 0. 05 95 0. 05 63 — 0. 05 14 0. 04 96 0. 04 46 2B 0. 04 65 0. 05 14 0. 05 19 0. 05 42 0. 06 00 3A 0. 00 00 0. 06 00 0. 05 68 — 0. 05 19 0. 05 06 0. 04 51 3B 0. 04 65 0. 05 14 0. 05 19 0. 05 36 0. 06 00 1– 64 U N C 2A 0. 00 06 0. 07 24 0. 06 86 — 0. 06 23 0. 06 03 0. 05 38 2B 0. 05 61 0. 06 23 0. 06 29 0. 06 55 0. 07 30 3A 0. 00 00 0. 07 30 0. 06 92 — 0. 06 29 0. 06 14 0. 05 44 3B 0. 05 61 0. 06 23 0. 06 29 0. 06 48 0. 07 30 1– 72 U N F 2A 0. 00 06 0. 07 24 0. 06 89 — 0. 06 34 0. 06 15 0. 05 59 2B 0. 05 80 0. 06 35 0. 06 40 0. 06 65 0. 07 30 3A 0. 00 00 0. 07 30 0. 06 95 — 0. 06 40 0. 06 26 0. 05 65 3B 0. 05 80 0. 06 35 0. 06 40 0. 06 59 0. 07 30 2– 56 U N C 2A 0. 00 06 0. 08 54 0. 08 13 — 0. 07 38 0. 07 17 0. 06 42 2B 0. 06 67 0. 07 37 0. 07 44 0. 07 72 0. 08 60 3A 0. 00 00 0. 08 60 0. 08 19 — 0. 07 44 0. 07 28 0. 06 48 3B 0. 06 67 0. 07 37 0. 07 44 0. 07 65 0. 08 60 2– 64 U N F 2A 0. 00 06 0. 08 54 0. 08 16 — 0. 07 53 0. 07 33 0. 06 68 2B 0. 06 91 0. 07 53 0. 07 59 0. 07 86 0. 08 60 3A 0. 00 00 0. 08 60 0. 08 22 — 0. 07 59 0. 07 44 0. 06 74 3B 0. 06 91 0. 07 53 0. 07 59 0. 07 79 0. 08 60 3– 48 U N C 2A 0. 00 07 0. 09 83 0. 09 38 — 0. 08 48 0. 08 25 0. 07 34 2B 0. 07 64 0. 08 45 0. 08 55 0. 08 85 0. 09 90 3A 0. 00 00 0. 09 90 0. 09 45 — 0. 08 55 0. 08 38 0. 07 41 3B 0. 07 64 0. 08 45 0. 08 55 0. 08 77 0. 09 90 3– 56 U N F 2A 0. 00 07 0. 09 83 0. 09 42 — 0. 08 67 0. 08 45 0. 07 71 2B 0. 07 97 0. 08 65 0. 08 74 0. 09 02 0. 09 90 3A 0. 00 00 0. 09 90 0. 09 49 — 0. 08 74 0. 08 58 0. 07 78 3B 0. 07 97 0. 08 65 0. 08 74 0. 08 95 0. 09 90 4– 40 U N C 2A 0. 00 08 0. 11 12 0. 10 61 — 0. 09 50 0. 09 25 0. 08 14 2B 0. 08 49 0. 09 39 0. 09 58 0. 09 91 0. 11 20 3A 0. 00 00 0. 11 20 0. 10 69 — 0. 09 58 0. 09 39 0. 08 22 3B 0. 08 49 0. 09 39 0. 09 58 0. 09 82 0. 11 20 4– 48 U N F 2A 0. 00 07 0. 11 13 0. 10 68 — 0. 09 78 0. 09 54 0. 08 64 2B 0. 08 94 0. 09 68 0. 09 85 0. 10 16 0. 11 20 3A 0. 00 00 0. 11 20 0. 10 75 — 0. 09 85 0. 09 67 0. 08 71 3B 0. 08 94 0. 09 68 0. 09 85 0. 10 08 0. 11 20 5– 40 U N C 2A 0. 00 08 0. 12 42 0. 11 91 — 0. 10 80 0. 10 54 0. 09 44 2B 0. 09 79 0. 10 62 0. 10 88 0. 11 21 0. 12 50 3A 0. 00 00 0. 12 50 0. 11 99 — 0. 10 88 0. 10 69 0. 09 52 3B 0. 09 79 0. 10 62 0. 10 88 0. 11 13 0. 12 50 5– 44 U N F 2A 0. 00 07 0. 12 43 0. 11 95 — 0. 10 95 0. 10 70 0. 09 72 2B 0. 10 04 0. 10 79 0. 11 02 0. 11 34 0. 12 50 3A 0. 00 00 0. 12 50 0. 12 02 — 0. 11 02 0. 10 83 0. 09 79 3B 0. 10 04 0. 10 79 0. 11 02 0. 11 26 0. 12 50 6– 32 U N C 2A 0. 00 08 0. 13 72 0. 13 12 — 0. 11 69 0. 11 41 0. 10 00 2B 0. 10 4 0. 11 4 0. 11 77 0. 12 14 0. 13 80 3A 0. 00 00 0. 13 80 0. 13 20 — 0. 11 77 0. 11 56 0. 10 08 3B 0. 10 40 0. 11 40 0. 11 77 0. 12 04 0. 13 80 6– 40 U N F 2A 0. 00 08 0. 13 72 0. 13 21 — 0. 12 10 0. 11 84 0. 10 74 2B 0. 11 1 0. 11 9 0. 12 18 0. 12 52 0. 13 80 3A 0. 00 00 0. 13 80 0. 13 29 — 0. 12 18 0. 11 98 0. 10 82 3B 0. 11 10 0. 11 86 0. 12 18 0. 12 43 0. 13 80 8– 32 U N C 2A 0. 00 09 0. 16 31 0. 15 71 — 0. 14 28 0. 13 99 0. 12 59 2B 0. 13 0 0. 13 9 0. 14 37 0. 14 75 0. 16 40 3A 0. 00 00 0. 16 40 0. 15 80 — 0. 14 37 0. 14 15 0. 12 68 3B 0. 13 00 0. 13 89 0. 14 37 0. 14 65 0. 16 40 8– 36 U N F 2A 0. 00 08 0. 16 32 0. 15 77 — 0. 14 52 0. 14 24 0. 13 01 2B 0. 13 4 0. 14 2 0. 14 60 0. 14 96 0. 16 40 3A 0. 00 00 0. 16 40 0. 15 85 — 0. 14 60 0. 14 39 0. 13 09 3B 0. 13 40 0. 14 16 0. 14 60 0. 14 87 0. 16 40 M ac hi ne ry 's H an db oo k 27 th E di ti on C op yr ig ht 2 00 4, I nd us tr ia l P re ss , I nc ., N ew Y or k, N Y UNIFIED SCREW THREADS 1737 10 –2 4 U N C 2A 0. 00 10 0. 18 90 0. 18 18 — 0. 16 19 0. 15 86 0. 13 94 2B 0. 14 5 0. 15 6 0. 16 29 0. 16 72 0. 19 00 3A 0. 00 00 0. 19 00 0. 18 28 — 0. 16 29 0. 16 04 0. 14 04 3B 0. 14 50 0. 15 55 0. 16 29 0. 16 61 0. 19 00 10 –2 8 U N S 2A 0. 00 10 0. 18 90 0. 18 25 — 0. 16 58 0. 16 25 0. 14 64 2B 0. 15 1 0. 16 0 0. 16 68 0. 17 11 0. 19 00 10 –3 2 U N F 2A 0. 00 09 0. 18 91 0. 18 31 — 0. 16 88 0. 16 58 0. 15 19 2B 0. 15 6 0. 16 4 0. 16 97 0. 17 36 0. 19 00 3A 0. 00 00 0. 19 00 0. 18 40 — 0. 16 97 0. 16 74 0. 15 28 3B 0. 15 60 0. 16 41 0. 16 97 0. 17 26 0. 19 00 10 –3 6 U N S 2A 0. 00 09 0. 18 91 0. 18 36 — 0. 17 11 0. 16 81 0. 15 60 2B 0. 16 0 0. 16 6 0. 17 20 0. 17 59 0. 19 00 10 –4 0 U N S 2A 0. 00 09 0. 18 91 0. 18 40 — 0. 17 29 0. 17 00 0. 15 92 2B 0. 16 3 0. 16 9 0. 17 38 0. 17 75 0. 19 00 10 –4 8 U N S 2A 0. 00 08 0. 18 92 0. 18 47 — 0. 17 57 0. 17 31 0. 16 44 2B 0. 16 7 0. 17 2 0. 17 65 0. 17 99 0. 19 00 10 –5 6 U N S 2A 0. 00 07 0. 18 93 0. 18 52 — 0. 17 77 0. 17 52 0. 16 81 2B 0. 17 1 0. 17 5 0. 17 84 0. 18 16 0. 19 00 12 –2 4 U N C 2A 0. 00 10 0. 21 50 0. 20 78 — 0. 18 79 0. 18 45 0. 16 54 2B 0. 17 1 0. 18 1 0. 18 89 0. 19 33 0. 21 60 3A 0. 00 00 0. 21 60 0. 20 88 — 0. 18 89 0. 18 63 0. 16 64 3B 0. 17 10 0. 18 07 0. 18 89 0. 19 22 0. 21 60 12 –2 8 U N F 2A 0. 00 10 0. 21 50 0. 20 85 — 0. 19 18 0. 18 86 0. 17 24 2B 0. 17 7 0. 18 6 0. 19 28 0. 19 70 0. 21 60 3A 0. 00 00 0. 21 60 0. 20 95 — 0. 19 28 0. 19 04 0. 17 34 3B 0. 17 70 0. 18 57 0. 19 28 0. 19 59 0. 21 60 12 –3 2 U N EF 2A 0. 00 09 0. 21 51 0. 20 91 — 0. 19 48 0. 19 17 0. 17 79 2B 0. 18 2 0. 19 0 0. 19 57 0. 19 98 0. 21 60 3A 0. 00 00 0. 21 60 0. 21 00 — 0. 19 57 0. 19 33 0. 17 88 3B 0. 18 20 0. 18 95 0. 19 57 0. 19 88 0. 21 60 12 –3 6 U N S 2A 0. 00 09 0. 21 51 0. 20 96 — 0. 19 71 0. 19 41 0. 18 21 2B 0. 18 6 0. 19 2 0. 19 80 0. 20 19 0. 21 60 12 –4 0 U N S 2A 0. 00 09 0. 21 51 0. 21 00 — 0. 19 89 0. 19 60 0. 18 35 2B 0. 18 9 0. 19 5 0. 19 98 0. 20 35 0. 21 60 12 –4 8 U N S 2A 0. 00 08 0. 21 52 0. 21 07 — 0. 20 17 0. 19 91 0. 19 04 2B 0. 19 3 0. 19 8 0. 20 25 0. 20 59 0. 21 60 12 –5 6 U N S 2A 0. 00 07 0. 21 53 0. 21 12 — 0. 20 37 0. 20 12 0. 19 41 2B 0. 19 7 0. 20 1 0. 20 44 0. 20 76 0. 21 60 1 ⁄ 4 – 20 U N C 1A 0. 00 11 0. 24 89 0. 23 67 — 0. 21 64 0. 21 08 0. 18 94 1B 0. 19 6 0. 20 7 0. 21 75 0. 22 48 0. 25 00 2A 0. 00 11 0. 24 89 0. 24 08 0. 23 67 0. 21 64 0. 21 27 0. 18 94 2B 0. 19 6 0. 20 7 0. 21 75 0. 22 24 0. 25 00 3A 0. 00 00 0. 25 00 0. 24 19 — 0. 21 75 0. 21 47 0. 19 05 3B 0. 19 60 0. 20 67 0. 21 75 0. 22 11 0. 25 00 1 ⁄ 4 – 24 U N S 2A 0. 00 11 0. 24 89 0. 24 17 — 0. 22 18 0. 21 81 0. 19 93 2B 0. 20 5 0. 21 5 0. 22 29 0. 22 77 0. 25 00 1 ⁄ 4 – 27 U N S 2A 0. 00 10 0. 24 90 0. 24 23 — 0. 22 49 0. 22 14 0. 20 49 2B 0. 21 0 0. 21 9 0. 22 59 0. 23 04 0. 25 00 1 ⁄ 4 – 28 U N F 1A 0. 00 10 0. 24 90 0. 23 92 — 0. 22 58 0. 22 08 0. 20 64 1B 0. 21 1 0. 22 0 0. 22 68 0. 23 33 0. 25 00 2A 0. 00 10 0. 24 90 0. 24 25 — 0. 22 58 0. 22 25 0. 20 64 2B 0. 21 1 0. 22 0 0. 22 68 0. 23 11 0. 25 00 3A 0. 00 00 0. 25 00 0. 24 35 — 0. 22 68 0. 22 43 0. 20 74 3B 0. 21 10 0. 21 90 0. 22 68 0. 23 00 0. 25 00 1 ⁄ 4 – 32 U N EF 2A 0. 00 10 0. 24 90 0. 24 30 — 0. 22 87 0. 22 55 0. 21 18 2B 0. 21 6 0. 22 4 0. 22 97 0. 23 39 0. 25 00 3A 0. 00 00 0. 25 00 0. 24 40 — 0. 22 97 0. 22 73 0. 21 28 3B 0. 21 60 0. 22 29 0. 22 97 0. 23 28 0. 25 00 Ta bl e 3 . (C on tin ue d) St an da rd S er ie s a nd S el ec te d C om bi na tio ns — U ni fie d Sc re w T hr ea ds N om in al S iz e, Th re ad s p er In ch , an d Se rie s D es ig na tio na Ex te rn al b In te rn al b Cl as s A llo w - an ce M ajo r D iam ete r Pi tc h D ia m et er U N R M in or D ia .,c M ax (R ef. ) Cl as s M in or D ia m et er Pi tc h D ia m et er M ajo r D ia m et er M ax d M in M in e M ax d M in M in M ax M in M ax M in M ac hi ne ry 's H an db oo k 27 th E di ti on C op yr ig ht 2 00 4, I nd us tr ia l P re ss , I nc ., N ew Y or k, N Y ZHUDAN 线条 ZHUDAN 线条 UNIFIED SCREW THREADS1738 1 ⁄ 4 – 36 U N S 2A 0. 00 09 0. 24 91 0. 24 36 — 0. 23 11 0. 22 80 0. 21 61 2B 0. 22 0 0. 22 6 0. 23 20 0. 23 60 0. 25 00 1 ⁄ 4 – 40 U N S 2A 0. 00 09 0. 24 91 0. 24 40 — 0. 23 29 0. 23 00 0. 21 93 2B 0. 22 3 0. 22 9 0. 23 38 0. 23 76 0. 25 00 1 ⁄ 4 – 48 U N S 2A 0. 00 08 0. 24 92 0. 24 47 — 0. 23 57 0. 23 30 0. 22 43 2B 0. 22 7 0. 23 2 0. 23 65 0. 24 01 0. 25 00 1 ⁄ 4 – 56 U N S 2A 0. 00 08 0. 24 92 0. 24 51 — 0. 23 76 0. 23 50 0. 22 80 2B 0. 23 1 0. 23 5 0. 23 84 0. 24 17 0. 25 00 5 ⁄ 1 6– 18 U N C 1A 0. 00 12 0. 31 13 0. 29 82 — 0. 27 52 0. 26 91 0. 24 52 1B 0. 25 2 0. 26 5 0. 27 64 0. 28 43 0. 31 25 2A 0. 00 12 0. 31 13 0. 30 26 0. 29 82 0. 27 52 0. 27 12 0. 24 52 2B 0. 25 2 0. 26 5 0. 27 64 0. 28 17 0. 31 25 3A 0. 00 00 0. 31 25 0. 30 38 — 0. 27 64 0. 27 34 0. 24 64 3B 0. 25 20 0. 26 30 0. 27 64 0. 28 03 0. 31 25 5 ⁄ 1 6– 20 U N 2A 0. 00 12 0. 31 13 0. 30 32 — 0. 27 88 0. 27 48 0. 25 18 2B 0. 25 8 0. 27 0 0. 28 00 0. 28 52 0. 31 25 3A 0. 00 00 0. 31 25 0. 30 44 — 0. 28 00 0. 27 70 0. 25 30 3B 0. 25 80 0. 26 80 0. 28 00 0. 28 39 0. 31 25 5 ⁄ 1 6– 24 U N F 1A 0. 00 11 0. 31 14 0. 30 06 — 0. 28 43 0. 27 88 0. 26 18 1B 0. 26 7 0. 27 7 0. 28 54 0. 29 25 0. 31 25 2A 0. 00 11 0. 31 14 0. 30 42 — 0. 28 43 0. 28 06 0. 26 18 2B 0. 26 7 0. 27 7 0. 28 54 0. 29 02 0. 31 25 3A 0. 00 00 0. 31 25 0. 30 53 — 0. 28 54 0. 28 27 0. 26 29 3B 0. 26 70 0. 27 54 0. 28 54 0. 28 90 0. 31 25 5 ⁄ 1 6– 27 U N S 2A 0. 00 10 0. 31 15 0. 30 48 — 0. 28 74 0. 28 39 0. 26 74 2B 0. 27 2 0. 28 1 0. 28 84 0. 29 29 0. 31 25 5 ⁄ 1 6– 28 U N 2A 0. 00 10 0. 31 15 0. 30 50 — 0. 28 83 0. 28 49 0. 26 89 2B 0. 27 4 0. 28 2 0. 28 93 0. 29 37 0. 31 25 3A 0. 00 00 0. 31 25 0. 30 60 — 0. 28 93 0. 28 67 0. 26 99 3B 0. 27 40 0. 28 07 0. 28 93 0. 29 26 0. 31 25 5 ⁄ 1 6– 32 U N EF 2A 0. 00 10 0. 31 15 0. 30 55 — 0. 29 12 0. 28 80 0. 27 43 2B 0. 27 9 0. 28 6 0. 29 22 0. 29 64 0. 31 25 3A 0. 00 00 0. 31 25 0. 30 65 — 0. 29 22 0. 28 98 0. 27 53 3B 0. 27 90 0. 28 47 0. 29 22 0. 29 53 0. 31 25 5 ⁄ 1 6– 36 U N S 2A 0. 00 09 0. 31 16 0. 30 61 — 0. 29 36 0. 29 05 0. 27 85 2B 0. 28 2 0. 28 9 0. 29 45 0. 29 85 0. 31 25 5 ⁄ 1 6– 40 U N S 2A 0. 00 09 0. 31 16 0. 30 65 — 0. 29 54 0. 29 25 0. 28 18 2B 0. 28 5 0. 29 1 0. 29 63 0. 30 01 0. 31 25 5 ⁄ 1 6– 48 U N S 2A 0. 00 08 0. 31 17 0. 30 72 — 0. 29 82 0. 29 55 0. 28 69 2B 0. 29 0 0. 29 5 0. 29 90 0. 30 26 0. 31 25 3 ⁄ 8 – 16 U N C 1A 0. 00 13 0. 37 37 0. 35 95 — 0. 33 31 0. 32 66 0. 29 92 1B 0. 30 7 0. 32 1 0. 33 44 0. 34 29 0. 37 50 2A 0. 00 13 0. 37 37 0. 36 43 0. 35 95 0. 33 31 0. 32 87 0. 29 92 2B 0. 30 7 0. 32 1 0. 33 44 0. 34 01 0. 37 50 3A 0. 00 00 0. 37 50 0. 36 56 — 0. 33 44 0. 33 11 0. 30 05 3B 0. 30 70 0. 31 82 0. 33 44 0. 33 87 0. 37 50 3 ⁄ 8 – 18 U N S 2A 0. 00 13 0. 37 37 0. 36 50 — 0. 33 76 0. 33 33 0. 30 76 2B 0. 31 5 0. 32 8 0. 33 89 0. 34 45 0. 37 50 3 ⁄ 8 – 20 U N 2A 0. 00 12 0. 37 38 0. 36 57 — 0. 34 13 0. 33 72 0. 31 43 2B 0. 32 1 0. 33 2 0. 34 25 0. 34 79 0. 37 50 3A 0. 00 00 0. 37 50 0. 36 69 — 0. 34 25 0. 33 94 0. 31 55 3B 0. 32 10 0. 32 97 0. 34 25 0. 34 65 0. 37 50 Ta bl e 3 . (C on tin ue d) St an da rd S er ie s a nd S el ec te d C om bi na tio ns — U ni fie d Sc re w T hr ea ds N om in al S iz e, Th re ad s p er In ch , an d Se rie s D es ig na tio na Ex te rn al b In te rn al b Cl as s A llo w - an ce M ajo r D iam ete r Pi tc h D ia m et er U N R M in or D ia .,c M ax (R ef. ) Cl as s M in or D ia m et er Pi tc h D ia m et er M ajo r D ia m et er M ax d M in M in e M ax d M in M in M ax M in M ax M in M ac hi ne ry 's H an db oo k 27 th E di ti on C op yr ig ht 2 00 4, I nd us tr ia l P re ss , I nc ., N ew Y or k, N Y UNIFIED SCREW THREADS 1739 3 ⁄ 8 – 24 U N F 1A 0. 00 11 0. 37 39 0. 36 31 — 0. 34 68 0. 34 11 0. 32 43 1B 0. 33 0 0. 34 0 0. 34 79 0. 35 53 0. 37 50 2A 0. 00 11 0. 37 39 0. 36 67 — 0. 34 68 0. 34 30 0. 32 43 2B 0. 33 0 0. 34 0 0. 34 79 0. 35 28 0. 37 50 3 ⁄ 8 – 24 U N F 3A 0. 00 00 0. 37 50 0. 36 78 — 0. 34 79 0. 34 50 0. 32 54 3B 0. 33 00 0. 33 72 0. 34 79 0. 35 16 0. 37 50 3 ⁄ 8 – 27 U N S 2A 0. 00 11 0. 37 39 0. 36 72 — 0. 34 98 0. 34 62 0. 32 98 2B 0. 33 5 0. 34 4 0. 35 09 0. 35 56 0. 37 50 3 ⁄ 8 – 28 U N 2A 0. 00 11 0. 37 39 0. 36 74 — 0. 35 07 0. 34 71 0. 33 13 2B 0. 33 6 0. 34 5 0. 35 18 0. 35 64 0. 37 50 3A 0. 00 00 0. 37 50 0. 36 85 — 0. 35 18 0. 34 91 0. 33 24 3B 0. 33 60 0. 34 26 0. 35 18 0. 35 53 0. 37 50 3 ⁄ 8 – 32 U N EF 2A 0. 00 10 0. 37 40 0. 36 80 — 0. 35 37 0. 35 03 0. 33 68 2B 0. 34 1 0. 34 9 0. 35 47 0. 35 91 0. 37 50 3A 0. 00 00 0. 37 50 0. 36 90 — 0. 35 47 0. 35 22 0. 33 78 3B 0. 34 10 0. 34 69 0. 35 47 0. 35 80 0. 37 50 3 ⁄ 8 – 36 U N S 2A 0. 00 10 0. 37 40 0. 36 85 — 0. 35 60 0. 35 28 0. 34 09 2B 0. 34 5 0. 35 2 0. 35 70 0. 36 12 0. 37 50 3 ⁄ 8 – 40 U N S 2A 0. 00 09 0. 37 41 0. 36 90 — 0. 35 79 0. 35 48 0. 34 43 2B 0. 34 8 0. 35 4 0. 35 88 0. 36 28 0. 37 50 0. 39 0– 27 U N S 2A 0. 00 11 0. 38 89 0. 38 22 — 0. 36 48 0. 36 12 0. 34 48 2B 0. 35 0 0. 35 9 0. 36 59 0. 37 06 0. 39 00 7 ⁄ 1 6– 14 U N C 1A 0. 00 14 0. 43 61 0. 42 06 — 0. 38 97 0. 38 26 0. 35 11 1B 0. 36 0