Schaublin 13 – change gear train for helical milling

[Adam HarrisParticipant @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.

[Adam HarrisParticipant @adamharris13683]

[Adam HarrisParticipant @adamharris13683]

photo of original helical milling attachment in photos

[BazyleParticipant @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.

[Adam HarrisParticipant @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?

[SteveIParticipant @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

[Adam HarrisParticipant @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

[SteveIParticipant @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

[Adam HarrisParticipant @adamharris13683]

Hi Steve, thanks – I have PM'd you

[SteveIParticipant @stevei]

Adam,

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

Steve

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