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Noticing recent posts mentioning 127 tooth conversion gears I thought it may be useful to show a different method using standard gears, namely a
54T pegged with a 44T giving a very close conversion for most thread lengths.
This is not my idea but taken from a site called Workshop Protects which seems to no longer exist, fortunately I took screenshots of it.
Attachment 19915
Attachment 19916
Hope someone finds this useful.
Olderdan
Do you have any idea what the foot notes are for the three astrichs? ***
Looks like the *** line got cut off on the screen shot.
I have this link tucked away for when I need to cut a metric thread on my old Logan lathe.
Metric Threading
Thanks Hemmjo, that is a very comprehensive article, thanks for the link.Quote:
Originally Posted by hemmjo
I think the three asterisks indicate a slightly increased error for those pitches but I have not done the maths.
No, three *** mean there is more info for it.
I would second Nelson's recommendation: the 37/44 tooth combination shown there yields a 1.2703:1 ratio: very close to the ideal 1.2700:1 ratio. according to Logan's web site, it's only 2/100s of 1% error. the 54/44 combo yields 1:2273:1.
Kudos to OlderDan for bringing this to the surface: an easy way for inch-based lathes to cut metric threads!
Your text in your writeup says 54:44 gear pairQuote:
Originally Posted by olderdan
54/44 = 1.2273
but the text in the picture you included seems to indicate 56/44
56/44 = 1.2727
which is, indeed, closer to the desired 1.2700000....
Was the "54" a typo or am I missing something here?
Of course, 47:37 is still a lot closer...
47/37 = 1.27027027
It was indeed a typo, thanks for pointing it out, probably would have been better to let the chart speak for itself.
I am sure there are better combinations but the chart is for standard SB change gears which are all of an even number.
Another typo I think...Quote:
Originally Posted by rebuilder1954
44/37 = 1.11892
The correct form is...
47/37 = 1.27027027...
Indeed that was a typo.
thanks, Marv, for the eagle eyes!
The GEARFIND program on my site allows the user to specify
desired ratio
allowable maximum ratio error
number of gear pairs to consider
minimum number of gear teeth
maximum number of gear teeth
It will then find all the gear arrangements within those limits that satisfy the ratio within the allowable error and write this information to an ASCII file that can be read or printed.
As an example, we can get a bit closer to the desired 1.270000... by using two pairs of gears instead of one. I had the program look for arrangements of gears with teeth in the range 16 - 40 that would provide the ratio with an error less than 0.01%. The output looks like this...
Before someone asks, let me explain the significance of the double asterisks (**) in the program output. As the program finds a solution that satisfies the user's criteria, it checks to see if that solution is better than the best solution it has found so far. If it is, it marks it with the double asterisks. Thus, the user, when examining the file, can simply scan down to the last entry marked with the asterisks to identify the best possible solution.Code:Desired ratio = 1.27
17:18-39:29- 1.27011 (0.00905059 %) **
17:29-39:18- 1.27011 (0.00905059 %) **
19:17-25:22- 1.27005 (0.0042107 %) **
19:22-25:17- 1.27005 (0.0042107 %)
22:19-34:31- 1.26995 (-0.00401053 %) **
22:31-34:19- 1.26995 (-0.00401053 %)
25:17-19:22- 1.27005 (0.0042107 %)
25:22-19:17- 1.27005 (0.0042107 %)
25:22-38:34- 1.27005 (0.0042107 %)
25:34-38:22- 1.27005 (0.0042107 %)
26:24-34:29- 1.27011 (0.00905059 %)
26:29-34:24- 1.27011 (0.00905059 %)
30:23-37:38- 1.27002 (0.00180183 %) **
30:38-37:23- 1.27002 (0.00180183 %)
31:28-39:34- 1.26996 (-0.00330841 %)
31:34-39:28- 1.26996 (-0.00330841 %)
34:19-22:31- 1.26995 (-0.00401053 %)
34:24-26:29- 1.27011 (0.00905059 %)
34:29-26:24- 1.27011 (0.00905059 %)
34:29-39:36- 1.27011 (0.00905059 %)
34:31-22:19- 1.26995 (-0.00401053 %)
34:36-39:29- 1.27011 (0.00905059 %)
37:23-30:38- 1.27002 (0.00180183 %)
37:38-30:23- 1.27002 (0.00180183 %)
38:22-25:34- 1.27005 (0.0042107 %)
38:34-25:22- 1.27005 (0.0042107 %)
39:18-17:29- 1.27011 (0.00905059 %)
39:28-31:34- 1.26996 (-0.00330841 %)
39:29-17:18- 1.27011 (0.00905059 %)
39:29-34:36- 1.27011 (0.00905059 %)
39:34-31:28- 1.26996 (-0.00330841 %)
39:36-34:29- 1.27011 (0.00905059 %)
Of course, if you're just making a metric bolt, you don't need better accuracy than the 47/37 combination provides. However, in situations that demand high accuracy you may want to keep this program in mind.
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What am I missing here?
It seems that everyone is looking for ways to avoid using a 127 tooth gear. Is there something wrong with using 127?
Tony, I don’t think anyone is saying there is something wrong with a 127T gear, we know that is the perfect choice if you have one.
I do not have one and can’t make one with my 60:1 dividing head and they are expensive to buy, hence the compromise approach. I also do not have CNC available.
OK, so that is what I was missing. Every lathe with an inch based lead screw that I have used had a 127 tooth gear and I assumed that was universal.Quote:
Originally Posted by olderdan
Couple of years ago I found small (24 kB) program 'SuperSpacer' and below is calculation for cutting 127 gears.Quote:
Originally Posted by olderdan
Tooth,Degrees,Minutes,Seconds
01, 002, 50, 04.72
02, 005, 40, 09.45
03, 008, 30, 14.17
04, 011, 20, 18.90
05, 014, 10, 23.62
06, 017, 00, 28.35
07, 019, 50, 33.07
08, 022, 40, 37.80
09, 025, 30, 42.52
10, 028, 20, 47.24
11, 031, 10, 51.97
12, 034, 00, 56.69
13, 036, 51, 01.42
14, 039, 41, 06.14
15, 042, 31, 10.87
16, 045, 21, 15.59
17, 048, 11, 20.31
18, 051, 01, 25.04
19, 053, 51, 29.76
20, 056, 41, 34.49
21, 059, 31, 39.21
22, 062, 21, 43.94
23, 065, 11, 48.66
24, 068, 01, 53.39
25, 070, 51, 58.11
26, 073, 42, 02.83
27, 076, 32, 07.56
28, 079, 22, 12.28
29, 082, 12, 17.01
30, 085, 02, 21.73
31, 087, 52, 26.46
32, 090, 42, 31.18
33, 093, 32, 35.91
34, 096, 22, 40.63
35, 099, 12, 45.35
36, 102, 02, 50.08
37, 104, 52, 54.80
38, 107, 43, -00.47
39, 110, 33, 04.25
40, 113, 23, 08.98
41, 116, 13, 13.70
42, 119, 03, 18.42
43, 121, 53, 23.15
44, 124, 43, 27.87
45, 127, 33, 32.60
46, 130, 23, 37.32
47, 133, 13, 42.05
48, 136, 03, 46.77
49, 138, 53, 51.50
50, 141, 43, 56.22
51, 144, 34, 00.94
52, 147, 24, 05.67
53, 150, 14, 10.39
54, 153, 04, 15.12
55, 155, 54, 19.84
56, 158, 44, 24.57
57, 161, 34, 29.29
58, 164, 24, 34.02
59, 167, 14, 38.74
60, 170, 04, 43.46
61, 172, 54, 48.19
62, 175, 44, 52.91
63, 178, 34, 57.64
64, 181, 25, 02.36
65, 184, 15, 07.09
66, 187, 05, 11.81
67, 189, 55, 16.53
68, 192, 45, 21.26
69, 195, 35, 25.98
70, 198, 25, 30.71
71, 201, 15, 35.43
72, 204, 05, 40.16
73, 206, 55, 44.88
74, 209, 45, 49.61
75, 212, 35, 54.33
76, 215, 26, -00.95
77, 218, 16, 03.78
78, 221, 06, 08.50
79, 223, 56, 13.23
80, 226, 46, 17.95
81, 229, 36, 22.68
82, 232, 26, 27.40
83, 235, 16, 32.13
84, 238, 06, 36.85
85, 240, 56, 41.57
86, 243, 46, 46.30
87, 246, 36, 51.02
88, 249, 26, 55.75
89, 252, 17, 00.47
90, 255, 07, 05.20
91, 257, 57, 09.92
92, 260, 47, 14.64
93, 263, 37, 19.37
94, 266, 27, 24.09
95, 269, 17, 28.82
96, 272, 07, 33.54
97, 274, 57, 38.27
98, 277, 47, 42.99
99, 280, 37, 47.72
100, 283, 27, 52.44
101, 286, 17, 57.16
102, 289, 08, 01.89
103, 291, 58, 06.61
104, 294, 48, 11.34
105, 297, 38, 16.06
106, 300, 28, 20.79
107, 303, 18, 25.51
108, 306, 08, 30.24
109, 308, 58, 34.96
110, 311, 48, 39.68
111, 314, 38, 44.41
112, 317, 28, 49.13
113, 320, 18, 53.86
114, 323, 08, 58.58
115, 325, 59, 03.31
116, 328, 49, 08.03
117, 331, 39, 12.75
118, 334, 29, 17.48
119, 337, 19, 22.20
120, 340, 09, 26.93
121, 342, 59, 31.65
122, 345, 49, 36.38
123, 348, 39, 41.10
124, 351, 29, 45.83
125, 354, 19, 50.55
126, 357, 09, 55.27
127, 360, 00, 00.00
So, if you have enough patience and decent rotary table you can do it.
Regards
LMMasterMariner
Screenshot of SuperSpacer program and a reason why I am not watching any video clips at youtube.
Regards
LMMasterMariner
The ROTARY program, free from my site, will do the same thing and won't be blacklisted.
Code:Number of divisions = 127
DIVISION degdec deg min sec
0 0.0000 0 0 0
1 2.8346 2 50 5
2 5.6693 5 40 9
3 8.5039 8 30 14
4 11.3386 11 20 19
5 14.1732 14 10 24
6 17.0079 17 0 28
7 19.8425 19 50 33
8 22.6772 22 40 38
9 25.5118 25 30 43
10 28.3465 28 20 47
11 31.1811 31 10 52
12 34.0157 34 0 57
13 36.8504 36 51 1
14 39.6850 39 41 6
15 42.5197 42 31 11
16 45.3543 45 21 16
17 48.1890 48 11 20
18 51.0236 51 1 25
19 53.8583 53 51 30
20 56.6929 56 41 34
21 59.5276 59 31 39
22 62.3622 62 21 44
23 65.1969 65 11 49
24 68.0315 68 1 53
25 70.8661 70 51 58
26 73.7008 73 42 3
27 76.5354 76 32 8
28 79.3701 79 22 12
29 82.2047 82 12 17
30 85.0394 85 2 22
31 87.8740 87 52 26
32 90.7087 90 42 31
33 93.5433 93 32 36
34 96.3780 96 22 41
35 99.2126 99 12 45
36 102.0472 102 2 50
37 104.8819 104 52 55
38 107.7165 107 43 0
39 110.5512 110 33 4
40 113.3858 113 23 9
41 116.2205 116 13 14
42 119.0551 119 3 18
43 121.8898 121 53 23
44 124.7244 124 43 28
45 127.5591 127 33 33
46 130.3937 130 23 37
47 133.2283 133 13 42
48 136.0630 136 3 47
49 138.8976 138 53 51
50 141.7323 141 43 56
51 144.5669 144 34 1
52 147.4016 147 24 6
53 150.2362 150 14 10
54 153.0709 153 4 15
55 155.9055 155 54 20
56 158.7402 158 44 25
57 161.5748 161 34 29
58 164.4094 164 24 34
59 167.2441 167 14 39
60 170.0787 170 4 43
61 172.9134 172 54 48
62 175.7480 175 44 53
63 178.5827 178 34 58
64 181.4173 181 25 2
65 184.2520 184 15 7
66 187.0866 187 5 12
67 189.9213 189 55 17
68 192.7559 192 45 21
69 195.5906 195 35 26
70 198.4252 198 25 31
71 201.2598 201 15 35
72 204.0945 204 5 40
73 206.9291 206 55 45
74 209.7638 209 45 50
75 212.5984 212 35 54
76 215.4331 215 25 59
77 218.2677 218 16 4
78 221.1024 221 6 9
79 223.9370 223 56 13
80 226.7717 226 46 18
81 229.6063 229 36 23
82 232.4409 232 26 27
83 235.2756 235 16 32
84 238.1102 238 6 37
85 240.9449 240 56 42
86 243.7795 243 46 46
87 246.6142 246 36 51
88 249.4488 249 26 56
89 252.2835 252 17 0
90 255.1181 255 7 5
91 257.9528 257 57 10
92 260.7874 260 47 15
93 263.6220 263 37 19
94 266.4567 266 27 24
95 269.2913 269 17 29
96 272.1260 272 7 34
97 274.9606 274 57 38
98 277.7953 277 47 43
99 280.6299 280 37 48
100 283.4646 283 27 52
101 286.2992 286 17 57
102 289.1339 289 8 2
103 291.9685 291 58 7
104 294.8031 294 48 11
105 297.6378 297 38 16
106 300.4724 300 28 21
107 303.3071 303 18 26
108 306.1417 306 8 30
109 308.9764 308 58 35
110 311.8110 311 48 40
111 314.6457 314 38 44
112 317.4803 317 28 49
113 320.3150 320 18 54
114 323.1496 323 8 59
115 325.9843 325 59 3
116 328.8189 328 49 8
117 331.6535 331 39 13
118 334.4882 334 29 17
119 337.3228 337 19 22
120 340.1575 340 9 27
121 342.9921 342 59 32
122 345.8268 345 49 36
123 348.6614 348 39 41
124 351.4961 351 29 46
125 354.3307 354 19 51
126 357.1654 357 9 55
127 360.0000 0 0 0
SuperSpacer is working fine. I downloaded it couple of years ago. But I am having problems with youtube recently. That web page is blacklisted.
Must check your web site. Thanks for sharing.
Regards
LMMasterMariner
Yes you really do need to check Marv's web site but be prepared to climb down the rabbit hole and spend some time there
