~.-.-- "\ j sc E I G (WITH ENGUSH GEARBOX &- 4 T.p.m. lEADSCREW) Metric Threads. For lathes not fitted with a lever operated English/Metric conversion unit extra change- wheels can be supplied covering a thread range of 0'5 - 7 m/m. Additional wheels required are 48T, 60T, 63T and I27T. Combinations are given on Chart 231. American Pipe Threads. The complete range of pipe threads is directly available through the gearbox with the exception of I I -~ and 27 TPI: the additional changewheels required for these, together with their combinations, are shown on chart. Special Threads.
Changewheels can be provided for comprehensive ranges of B.A., module, diametral, fractional and many other special thread pitches. METRiC SCREWCUTTING CHART RANGE Of T.I".!. , MEIR.lc I TOP I INTER· \ BOTTOM P~~~ SHAFT MEDIATE SHAFT SHAFT T.P.L POSiTION Ii 0...1:;: 'I "'~I:;: 1 6 1:;: I ."'6 0 "'- f- cow- RANGE T.P.L f-l: ~8l: til:
0G:;~ 'Ion, -:LV> ",V> -'2 1--- -----1 Standard 4 to 60 30 120 I 60 As,...G h· Box i----' ________ 1 '- art Fine I 64 to 120 30 80 I 120 " I ·5 60 48-60 I 127 I I ·75 60 48-60 127 I I 1 I 60 48-60 127 I I I , I I AD4 AD9 AC9 * " t Coarse I 2 to 3i 60 I 120 I 30 Spedal I 11t 60 1 60 115 BD6 Threads 27 1"4O'1~, 60 AD2 I 1·25 60 48-60 I 127 I 1·5 I 60 I 48-60 I AC6 J 127 1·75 1 63 I 48-60 127 I 2 I AC4 60 48-60 I 127 2·5 60 48-60 127 I 1 3 I 60 I AC2 BD9 * G B T Pie 't' _ T.P.1. Required . ox . . OSI Ion - 2 t G. Box T.P.I. Position = T.P.I. Required X 4 BD6 COMPLETE RANGE OIF T.P'!.
48-60 1 127 I 3·5 I 63 48-60 I 127 4 I 60 I 48-60 I 127 4·5 I 63 I I I 48-60 I 127 I 5 I 60 BD4 Coarse I I 1 II 3 "I 3' 1 I 1 3 (Additional) 2 2" 2. ~ 2" _3_ ~ ~ ~ BD2 r l 4 I. 44 5 I 52- 6 6' 7 7.l Standard 1' 13 1-'~-1-9-;- -1-0-1::::1::::~:::: -1-2- -1-~- -1-4- -1-~- !~I~I~I~i~~~I~~ 1----' l32 ,~i~'~!~I~~I~I~ Fine I i I '1 ! I (Additional)1 64 i 7: .~i .. 80 !~II'~I.~~~ S pedal i 11 i I 21 i I !. I BC9 BC8 1 48-60 I 127 I 1 I I i , i I 6 I 60 I 48-60 ! 127 BC6 BC4 1 I 63 48-60 i 127 I I No. 231 I~- 1 I BC2 ---- Warning: When cutting threads coarser than f' pitch it is advisable to engage the half nuts with the spindle stationary, then engage the clutch.
The use of the lowest spindle speed is essentiaL The maximum pitch that can be cut on a centre lathe is determined by the diameter and depth of cut required. The recolTilllended maximum r.~!ix for roughing is go and a light cut up to I00 - 12°. The cutting of a coarse thread should only be carried out by a skilled operator who will appreciate the limitations imposed by the conditions which will vary according to the type of material, thread and depth of cut, etc. 12