METRIC/BA THREAD CHART

Metric/BA screwcutting chart for imperial lathes

Here's a useful chart for screwcutting metric and B.A. threads on an
imperial lathe by using a 63-tooth conversion gear. Very close 
approximations to the required pitchs are achievable using the standard
set of gears plus the conversion gear.

SCREW CUTTING CHART (metric threads)
25-tooth driver on spindle, 8 T.P.I. leadscrew.
------------------------------------------------
Pitch of      Driver Wheels	  Driven Wheels	    Exact Pitch
thread		B	D	A	C	E	(mm)
0.20		25	20	40	63	70	0.2000
0.25		25	20	35	65	70	0.2492
0.30		25	20	30	63	70	0.3000
0.35		25	20	30	60	63	0.3500
0.40		25	20	35	45	63	0.4000
0.45		25	50	20	63	70	0.4500
0.50		25	20	45	63	70	0.5000
0.60		25	20	30	35	63	0.6000
0.70		25	20	20	45	63	0.7000
0.75		25	50	30	63	70	0.7500
0.80		20	50	35	45	63	0.8000
0.90		25	20	20	35	63	0.8999
1.00		25	50	35	45	63	0.9999
1.10		25	55	35	45	63	1.0999
1.20		20	50	30	35	63	1.1999
1.25		30	63	40	50	60	1.2502
1.30		25	65	35	45	63	1.2999
1.40		20	50	20	45	63	1.3999
1.50		25	50	30	35	63	1.4999
1.60		45	50	35	45	63	1.5999
1.75		25	50	20	45	63	1.7499
1.80		20	50	20	35	63	1.7999
2.00		30	63	20	50	75	2.0002
2.25		25	50	20	35	63	2.2499
2.50		20	63	20	40	50	2.5003
2.75		40	60	20	55	63	2.7489
3.00		50	75	35	45	63	2.9998
3.5		50	75	30	45	63	3.4998


SCREW CUTTING CHART (BA threads)
25-tooth driver on spindle, 8 T.P.I. leadscrew.
------------------------------------------------
B.A.	Nominal				 Driver		Exact
Thread	Threads   Driven wheels		 wheels		Threads
No.	per in.	A	B	D	C	E	per in.
0	25.40	40	50	75	30	63	25.40
1	28.22	38	45	65	20	63	28.23
2	31.36	38	50	65	20	63	31.36
3	34.79	55	60	75	35	65	34.81
4	38.48	30	63	70	20	55	38.49
5	43.05	50	70	75	30	65	43.08
6	47.92	35	55	70	20	45	47.91
7	52.92	45	63	70	20	60	52.92
8	59.07	40	55	63	25	30	59.14
9	65.13	60	63	70	20	65	65.13
10	72.57	30	60	63	20	25	72.58
11	81.94	25	63	65	20	20	81.90
12	90.71	30	60	63	20	20	90.72
13	101.60	35	65	70	20	25	101.92
14	110.43	40	55	63	20	20	110.88
15	120.95	40	60	63	20	20	120.96
16	133.68	60	65	75	20	35	133.71
17	149.41	45	55	75	20	20	148.50
18	169.33	60	63	70	20	25	169.34
19	181.43	60	63	75	20	25	181.44
20	211.67	60	63	70	20	20	211.68

*from: Metric and other threads from British lathes by
       Professor R. F. Cane
       Model Engineer (1980) 7-20 Mar, Vol 146, Num 3628
Metric/BA screwcutting chart for imperial lathes

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