I find an online calculator like this one useful.

It suggests that your plates will do 12,24,36,48,60,72, 84,108,120 but not 96! So its not all factors of 12 just (as murphy’s law requires) not the one you want.

The calculator suggest that a 12 (24, 36 or 48) hole plate would work, and you already have the plates necessary to make one. For a one off job I would be tempted to 3D print a plate with the necessary number of holes.

PS Edit – You could of course consider replacing the handle and index plates with a stepper motor and controller, then all these mathematical issues go away.

Sorry about the typo! That’s what happens when you proof read your own work!

As has been said above the easiest way would be to make a special 12 hole plate.

John

On 30 April 2026 at 19:08 Bazyle Said:

….I don’t think 63 is available….

Neither 63 nor 69 is available which annoyingly happened to be the tooth counts for the second shaft gears on my traction engines. Although I have a universal dividing head the easiest solution was to make my own dividing plate:

Julie

I wanted to get 118 for a scale conversion between 3mm and 1/8″ and ended up getting a spreadsheet with degrees and minutes printed out by Dick who is another volunteer at the museum.

Our Atlas 12 x 24 lathe has 60 holes in the bull gear which can be used for simple indexing and it divides by 5 to get twelve positions. 60 is a very useful number to have on a plate, I don’t remember if the three that I have have that count.

Some dividing heads have a direct indexing feature with eg 24 holes in the chuck backplate. Victoria did 4 extra plates if you didn’t want to go to differential indexing and included them in their tables.

If you have a 3D printer then on thingiverse there is an openscad utility that creates any count(s) complete with mounting holes etc to fit your dividing head.  https://www.thingiverse.com/thing:1908993

I showed an sample I did for 73 holes about 5 years ago.

On 30 April 2026 at 20:50 timdotd Said:

Sometimes all it takes to find the answer is to ask a daft question in public.

 

It is not a daft question. The 3DP idea is just a modern take on other older ideas.

It could be worth printing a (smaller) one hole plate as a test just to refine the indexing pin hole diameter.

Just a note here for anyone making their own plates – the biggest (and most common) issue I have found on the few home-made plates I have found is not the hole spacing but the concentricity between the centre hole and the index hole circle. It’s very important that these are concentric. If they are not then the holes on one side of the index hole circle will lag and the other side will lead their true index locations. Also the pin will not seat in some of the holes properly.

Good advice about checking index hole size and concentricity.

Although Julie referred to direct indexing there are a few (Elliotts being one mfr) that cater for a double sided index plate in the regular position for compound rather than differential indexing. I’ve not tried it as I don’t have a suitable plate but must now check whether I can print one.

I missed 9 holes on a 27 hole plate!

By using using the various hole spacings, various subdivisions of a turn can be produced

To see what divisions can be produced, using the Division Plates (Hence their name) take a look at the chart that I made for my 90:1 ratio Vertex HV6 Rotary rable, to correct errors in the one supplied with the device. I have used it to cut gears with tooth counts varying between 13 and 80, and to graduate dials (Usually 25 divisions to suit 10 tpi or 40 tpi threads)

You can make your own chart to suit your 40:1 device, (See below).

It does not cover every possibility between 1 and 100. (I ought to make up an extra plate or two to cover the missing divisions. (A TOMORROW job on the Round Tuit!)

The spreadsheet showing the formulae used, is also available.

No doubt, Neil Wyatt will be able to point you in the right direction to find it.

The calculations are the same except for the the ratio, in the formulae, needing to be changed from 90 to 40, to suit your device.

Howard

The OP wants 96 divisions not 12! A 12 hole plate would give the required 96 as 5/12 = 0.4.1666 x one turn of 9deg = 3.75deg.

96 x 3.75 =360

So 96 divisions means a division spacing of 3.75 dgrees, which requires 150 degrees rotation of the handle on a 40:1 machine. This is 0.4166′ of a turn of the handle.

Sadly, none of the division plates will give a 150 degrees rotation of the handle with an exact number of holes, so it will mean making a plate to provide this.

But 10 holes on a 24 hole plate will! (15 holes on a 36 hole plate, or 20 holes on a 48 hole plate)

All of these could be made on  plate of the same dimensions as the existing ones.

So now you need to find the Turns/holes combination to make 24, 36 or 48 divisions.  This might mean that you have to make a plate to make the required plate!

This could be fairly straightforward with a 90:1 ratio machine, but a 40:1 results, each time, in a non integer hole count. Which exchanges one problem for another! I had hoped that either the 16 or 20 hole plates, being divisible by 4, would have been the means. But not so!

On 1 May 2026 at 22:37 Howard Lewis Said:

So use the 18 hole plate to make a 24 hole plate, and use that one to give your 96 divisions!

It would be very useful to all of us if you would read the thread from the beginning and give your mind time to digest the previous responses before rattling the old typewriter.

Right now the thread has turned into Howard’s stream of conciousness – direct from brain to keyboard with no filter.

Please say what additional useful features are provided by a 24 hole plate that are not provided by a 12 hole plate. Why index and drill more holes than are necessary to achieve the aim?