Walter dividing head plate hole pattern

I picked up a Walter dividing head.

It's model HU 100.

You can see a video of someone restoring one here:
YouTube

I only have two of the three plates.
63,57,49,37,36,29,24,22
59,51,43,39,31,28,24,23

Kind of odd that they made the hole patterns this way, but I'm sure there's some logical reason. Interesting that 24 is on two of the plates.

I can make the third plate, but I have no idea what the holes should be.

On the video, I was able to see the third one had 61,53 and 47, but couldn't see any more than that.

I couldn't find information on any other dividing heads that had hole counts that matched these so that I could fill in the missing numbers.

Does anyone have one of these and can you tell me the hole counts?

If not, what divisions are missing?

I'm missing the prime number 41, so that's a likely candidate.

Other numbers I am missing in the sequence from 22 to 63 include:
25,26,27,30,32,33,34,35,38,40,41,42,44,45,46,47,48,50,52,53,54,55,56,58,60,61,62

I understand that some of these would not be needed, but don't know which ones.

Steve

May be of help. K&T Model H, was a 40:1 DH and used the first three rows as standard, and the following four as high number plates

Dividing is all about prime numbers. Most dividing heads have a 40:1 worm and the prime numbers in that ratio are: 2, 2, 2, and 5.

For any number of divisions that you want, you will have to have ALL of the prime numbers in that number in either the worm or in the plate. So, if you want 12 divisions you need 2, 2, and 3. The two 2s are in the worm so you need a plate with a hole circle that is a multiple of 3. Another example: if you want 127 divisions, that is a prime number. The worm is no help here and you need a plate with a 127 hole circle (or a multiple of that, like 254).

Some of the circles that you already have are composit numbers that contain a number of primes. For instance, you have a 24 hole circle which is 2, 2, 2, 3. So that, along with the worm, will allow you to make a bunch of divisions that are multiples of 3 (3, 6, 12, 15, 24, 30, 60, etc.) Other hole circles that you presently have are prime numbers and will only allow some multiples of that prime number. So, your 23 hole circle will allow you to divide by 23, 46, 92, 115, etc. (23 X 1, 2, 4, 5, etc.)

If you want to see what divisions you can make with the circles that you have, consult a table of factors of the integers. These tables will state which numbers are primes and which ones are composit while listing their prime factors. Every composit number has a unique set of prime factors. This is what the designers of the dividing heads and rotary tables do to determine what hole circles they will provide with them. Some prime numbers are not really very useful. You do not often need 51 or 97 divisions. So some circles are omitted. Quite often they stop including all divisions after 50. The "standard" plate sets referred to above will probably get you that far.

There is a procedure for making hole circles of any count from scratch, just using your dividing head and two or three sets of disks. I have explained it several times and a search of the board should turn up that explanation. Of course, there are other ways but they may not be as precise.

EPAIII said:

Dividing is all about prime numbers. Most dividing heads have a 40:1 worm and the prime numbers in that ratio are: 2, 2, 2, and 5.

For any number of divisions that you want, you will have to have ALL of the prime numbers in that number in either the worm or in the plate. So, if you want 12 divisions you need 2, 2, and 3. The two 2s are in the worm so you need a plate with a hole circle that is a multiple of 3. Another example: if you want 127 divisions, that is a prime number. The worm is no help here and you need a plate with a 127 hole circle (or a multiple of that, like 254).

Click to expand...

Thanks for that explanation!

Steve

So, the chart shown at:
Walter Dividing Head indexing plates question
shows plates with fewer holes in each than mine, probably because the particular head is smaller.

Those plates do not have the 22 and 36 that mine does.

The holes on those plates that I don't have are:
17,19,25,27,30,33,41,42,47,53,61

So I need to do some work to figure which eight out of that set would be needed and not duplicate what I can do with existing divisions.

Steve