Modern Machine-Shop Practice, Volumes I and II

by Joshua Rose

Fig. 1888.

Fig. 1888a.

The sector arms n and n′ may be opened apart or closed together so as to embrace any required number of holes in either of the circles. As shown in the cut they embrace one quarter of the circle of 20, there being five divisions between the holes s and t. The screw w secures them in their adjustment apart. Suppose that pin l ([Fig. 1887]), is in s, and arm n′ is moved up against it, the arm n leaves t open, and indicates that t is the next hole for pin l, which is withdrawn from s, and lever l ([Fig. 1887]) is moved around until the pin will enter t, and the sector is then moved into the position shown in [Fig. 1888a], indicating that hole u is the next one for the pin. This obviates the necessity of counting the holes, and prevents liability to error in the counting. Three of these index plates are provided, each having different numbers of holes in the circles, and in the following tables are given those specially prepared for use in cutting the teeth of gear-wheels:

No. of teeth.	Index circle.	No. of turns of index.		No. of teeth.	Index circle.	No. of turns of index.
2	ANY	20		80	20		10⁄20
3	39	13	13⁄39	82	41		20⁄41
4	ANY	10		84	21		10⁄21
5	„	8		85	17		8⁄17
6	39	6	26⁄39	86	43		20⁄43
7	49	5	35⁄49	88	33		15⁄33
8	ANY	5		90	27		12⁄27
9	27	4	12⁄27	92	23		10⁄23
10	ANY	4		94	47		20⁄47
11	33	3	21⁄33	95	19		8⁄19
12	39	3	13⁄39	98	49		20⁄49
13	39	3	3⁄39	100	20		8⁄20
14	49	2	42⁄49	104	39		15⁄39
15	39	2	26⁄39	108	27		10⁄27
16	20	2	10⁄20	110	33		12⁄33
17	17	2	6⁄17	115	23		8⁄23
18	27	2	6⁄27	116	29		10⁄29
19	19	2	2⁄19	120	39		13⁄39
20	ANY	2		124	31		10⁄31
21	21	1	19⁄21	128	16		6⁄16
22	33	1	27⁄37	130	39		12⁄39
23	23	1	17⁄23	132	33		10⁄33
24	39	1	26⁄39	135	27		8⁄27
25	20	1	12⁄20	136	17		5⁄17
26	39	1	21⁄39	140	49		14⁄49
27	27	1	13⁄27	144	18		5⁄18
28	49	1	21⁄49	145	29		8⁄29
29	29	1	11⁄29	148	37		10⁄37
30	39	1	13⁄39	150	15		4⁄15
31	31	1	9⁄31	152	19		5⁄19
32	20	1	5⁄20	155	31		8⁄31
33	33	1	7⁄33	156	39		10⁄39
34	17	1	3⁄17	160	20		5⁄20
35	49	1	7⁄49	164	41		10⁄41
36	27	1	3⁄27	165	33		8⁄33
37	37	1	3⁄37	168	21		5⁄21
38	19	1	1⁄19	170	17		4⁄17
39	39	1	1⁄39	172	43		10⁄43
40	ANY	1		180	27		6⁄27
41	41		40⁄41	184	23		5⁄23
42	21		20⁄21	185	37		8⁄37
43	43		40⁄43	188	47		10⁄47
44	33		30⁄33	190	19		4⁄19
45	27		24⁄27	195	39		8⁄39
46	23		20⁄23	196	49		10⁄49
47	47		04⁄47	200	20		4⁄20
48	18		15⁄18	205	41		8⁄41
49	49		20⁄49	210	21		4⁄21
50	20		16⁄20	215	43		8⁄43
52	39		30⁄39	216	27		6⁄27
54	27		20⁄27	220	33		6⁄33
55	33		24⁄33	230	23		4⁄23
56	49		35⁄49	232	29		5⁄29
58	29		20⁄29	235	47		8⁄47
60	39		26⁄39	240	18		3⁄18
62	31		20⁄31	245	49		8⁄49
64	16		10⁄16	248	31		5⁄31
65	39		24⁄39	260	39		6⁄39
66	33		20⁄33	264	33		5⁄33
68	17		10⁄17	270	27		4⁄27
70	49		28⁄49	280	49		7⁄49
72	27		15⁄27	290	29		4⁄29
74	37		20⁄37	296	37		5⁄37
75	15		8⁄15	300	15		2⁄15
76	19		10⁄19	310	31		4⁄31
78	39		20⁄39	312	39		5⁄39

Fig. 1889.