Schaublin 13 – change gear train for helical milling

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Schaublin 13 – change gear train for helical milling

This topic has 9 replies, 3 voices, and was last updated 6 January 2018 at 11:58 by SteveI.

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4 January 2018 at 22:47 #335380
Adam Harris
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@adamharris13683
There is a helical milling attachment that mounts to the right hand longitudinal handwheel shaft, in order to drive a universal dividing head. I would like to make a functionally similar change gear train on banjo and out of curiosity wonder if anyone can tell me what set of change gears came with the original attachment? I will be using an Elliott or Hoffman dividing head and will be making up a banjo with change gears for differential milling (the set for both Hoffmann and Elliott is 2×24, 28, 32, 40, 44, 48, 56, 64, 72,86,100), and would like to make the banjo purposed for additional use to take the drive off the handwheel shaft.
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4 January 2018 at 22:47 #18795
Adam Harris
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@adamharris13683
4 January 2018 at 23:02 #335381
Adam Harris
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@adamharris13683
photo of original helical milling attachment in photos
4 January 2018 at 23:23 #335383
Bazyle
Participant
@bazyle
The list you give is the standard set and it is impressive that they managed to come up with such an economical combination without recourse to excel or an 'app'. In the Elliott tables you will find they also use a 60 (for 201 but it's wrong anyway). The 86 is only used for 106 divisions so may not be vital for you.

For differential indexing the gears are just used for what are mostly simple ratios – eg 2:1, 3:2 etc (with a few exceptions like for 106) so any good set of wheels will actually do. As with screwcutting it is all about collecting multiples of primes.
5 January 2018 at 00:54 #335390
Adam Harris
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@adamharris13683
So for Helical/Spiral milling are there a small number of generic ratios of lateral movement to rotation movement that are used to creat standard helix/spirals?
5 January 2018 at 13:04 #335441
SteveI
Participant
@stevei
Hi Adam,

According to a 1961 manual for the 13 mill the accessories for spiral milling (a banjo that attaches to the table, a set of 14 gears and a cover) include the following gears:

24, 24, 28, 32, 36, 40, 48, 56, 64, 72, 80, 90, 96, 96

Also there is an extra set of gears to extend the range as follows:

22, 26, 29, 52, 80, 100, 112

these were of course designed to drive the Schaublin dividing head which has a 40:1 worm reduction ratio.

Steve
5 January 2018 at 16:38 #335483
Adam Harris
Participant
@adamharris13683
Hi Steve, that is really very helpful thank you. The Hoffman and the Elliott also have 40:1 worm reduction ratios. Do you have the accessory yourself, and if so is there any chance you could take a photo of the banjo? Adam
5 January 2018 at 18:16 #335508
SteveI
Participant
@stevei
Hi Adam,

I do not own the attachment. I would like to own one. The only person I "know" who has a 13 with this attachment is Gary of eccentric engineering fame. He took some pictures of it for me a while back. If you PM me your email I can send you what I have although please note it is very limited.

Edit for a correction. The attachment comprises 2 banjo's. As you will see from the pictures. It would be nice to get Gary to make a better drawing of them, I have not asked him as it's a long way off being needed by me. My 13 will be rebuilt including a full re-scrape when I get the time.

Steve

Edited By SteveI on 05/01/2018 18:20:25
5 January 2018 at 21:25 #335539
Adam Harris
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@adamharris13683
Hi Steve, thanks – I have PM'd you
6 January 2018 at 11:58 #335590
SteveI
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@stevei
Adam,

i have replied to your PM and sent you an email.

Steve
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