Dividing head from a gearbox

[DC31kParticipant @dc31k]

“The only set of tables I have are for a 90:1 ratio”.

Please could someone enlighten Neil that a Myford dividing head uses a 60:1 ratio, as indeed did GHT’s offering as indeed did his Super 7 bullwheel dividing attachment.

[SillyOldDufferModerator @sillyoldduffer]

I’m confused!  Presumably Neil Wyatt? And where did Neil say that?

Dave

[JasonBModerator @jasonb]

As Neil (editor) does not visit here much you would be better off sending a reply by email and he may even post it in Postbag as per the original enquiry

[cedric 1Participant @cedric]

GH Thomas’s book on making his dividing head has the most comprehensive chart you are likely to find for 60:1.

 

[BazyleParticipant @bazyle]

To clarify – The latest ME&W has a letter in Postbag Page 45 asking for tables for a 60:1 dividing head from a 94yr old who maybe does not frequent the internet. The editor Neil responded that he only had tables for 90:1, presumably for a rotary table.
Really someone with such a table, eg for the bull wheel dividing attachment from Hemingway, could email them to Neil to send to the person. It is probable that providing links to online calculators would not be suitable for this person.

[John HaineParticipant @johnhaine32865]

There’s a whole thread on here from which this is a set of tables for 60T.

[Graham MeekParticipant @grahammeek88282]

It is quite easy to work out any required divisions from the following formula

n=K/Z,

where n = No. of revolutions of the handle for one dividing move.

Z = No. of divisions required for one revolution of the Workpiece.

K = No. of revolutions of handle for one complete revolution of the workpiece.

ie for a simple 30 divisions 90/30 = 3 turns for each division. Life gets a little more complicated when the required number of divisions is leaves a fraction.

For 16 divisions 90/16 = 5 turns and 10/16, or 5/8. Thus any circle on the dividing plate which 8 will divide into will do. It just requires the factor of 8 to be multiplied by 5 to get the number of holes between the Sector Arms.

Choosing a non standard ratio, means additional work for the individual. The simplicity of using something already existing like a gearbox will always have a trade off. When compared to something which is designed to do that particular job.

Regards

Gray,

[noel shelleyParticipant @noelshelley55608]

WORKSHOP PRACTICE series No 42 page 93 onwards has tables for numerous ratios of reduction. Noel.

[Howard LewisParticipant @howardlewis46836]

90:1 means that the Dividing Head or Rotary Table rotates 4 degrees for one complete turn of the handle.

A 60:1 ratio means that the rotation per complete turn of the handle is increased to 6 degrees.

So, for a given number of divisions, (or angular rotation) on a 60:1 device, the handle will will require the rotation to be decreased by a third.

Using these basic facts, it should not be too difficult to make up an EXCEL spreadsheet

(Indeed copy the 90:1 table held by Neil and change the formula from 90 to 60 and the required result should appear)  Do some basic divisions to check the spreadsheet results.

It is basically simple arithmetic, rather than rocket science.

Howard

[SillyOldDufferModerator @sillyoldduffer]

Here’s the Postbag letter from Vol235, Issue4773, Feb2026.  Sorry about the blur, I wobbled! Just about readable, and the title typo made me smile.  Diving Head, eh!

Don wants a Divider Plate Chart for a 60:1 rotary table built to an ME article that Neil couldn’t find, and Neil says he only has a 90:1 chart.   He asks if readers are able to help.

Gray describes the maths needed to calculate a chart, and John Haine provides a link to AJohnW 2016 post, #239133, which published this chart:

I’ve reposted AJohnW’s chart here in hope Don will see it directly and PM’d a link to Neil so he can pass the info to Don or put it in the mag, whatever.

Now the team (not me) have solved the problem, the hard part seems to be getting the answer to Don!

Dave

[Bazyle]

On Bazyle Said:

…who maybe does not frequent the internet.

Please enlighten us how your comment stands in relation to the ‘via the website’ printed at the bottom of the letter.

[BazyleParticipant @bazyle]

Sorry DC3 I didn’t memorise the entire letter. I assumed that he had written to the magazine as anyone frequenting the internet could have done a search or, as seems to be the modern trend, slapped a query on Facebook.

[Michael GilliganParticipant @michaelgilligan61133]

Here’s a more legible copy of the letter:

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.

Note the reference to Don’s great granddaughter, who one might reasonably assume to be computer-literate.

MichaelG.

[TomkParticipant @tomk39956]

Link to 90:1 tables

https://www.stubmandrel.co.uk/images/Bits_and_pieces/Vertex1.pdf

[Graham Meek]

On Graham Meek Said:

It is quite easy to work out any required divisions from the following formula

n=K/Z,

where n = No. of revolutions of the handle for one dividing move.

Z = No. of divisions required for one revolution of the Workpiece.

K = No. of revolutions of handle for one complete revolution of the workpiece.

ie for a simple 30 divisions 90/30 = 3 turns for each division. Life gets a little more complicated when the required number of divisions is leaves a fraction.

For 16 divisions 90/16 = 5 turns and 10/16, or 5/8. Thus any circle on the dividing plate which 8 will divide into will do. It just requires the factor of 8 to be multiplied by 5 to get the number of holes between the Sector Arms.

Choosing a non standard ratio, means additional work for the individual. The simplicity of using something already existing like a gearbox will always have a trade off. When compared to something which is designed to do that particular job.

Regards

Gray,

I had better just add that when setting the Sector Arms for the number of holes. The hole that the Indexing Pin is occupying in is never counted.

This is something I do naturally from experience, and this did not occur to me until well after making my post above.

Regards

Gray,

[SillyOldDuffer]

On SillyOldDuffer Said:

Here’s the Postbag letter from Vol235, Issue4773, Feb2026.  Sorry about the blur, I wobbled! Just about readable, and the title typo made me smile.  Diving Head, eh!

Don wants a Divider Plate Chart for a 60:1 rotary table built to an ME article that Neil couldn’t find, and Neil says he only has a 90:1 chart.   He asks if readers are able to help.

Gray describes the maths needed to calculate a chart, and John Haine provides a link to AJohnW 2016 post, #239133, which published this chart:

I’ve reposted AJohnW’s chart here in hope Don will see it directly and PM’d a link to Neil so he can pass the info to Don or put it in the mag, whatever.

Now the team (not me) have solved the problem, the hard part seems to be getting the answer to Don!

Dave

I think you’ll need to dip your best goose feather quill in finest India ink and write a letter to Postbag. Don  age 93, does not seem to be a tech bro likely to see this forum.

[David FrithParticipant @davidfrith72923]

Harold Hall posted a chart for 60:1 dividing head in his book: “Dividing” Workshop Practice series number 37, page 101

[cedric 1]

On cedric 1 Said:

On SillyOldDuffer Said:

Here’s the Postbag letter from Vol235, Issue4773, Feb2026.  …

 

I’ve reposted AJohnW’s chart here in hope Don will see it directly and PM’d a link to Neil so he can pass the info to Don or put it in the mag, whatever.

Now the team (not me) have solved the problem, the hard part seems to be getting the answer to Don!

Dave

I think you’ll need to dip your best goose feather quill in finest India ink and write a letter to Postbag. Don  age 93, does not seem to be a tech bro likely to see this forum.

Excellent idea Cedric, why don’t you do it?

I’ve done my best to get the message through by PM’ing the editor.   Can’t tell Don himself, or his granddaughter, because I don’t know who they are.    And, based on the postbag letter, Don’s might be reading the forum.  The letter is tagged, “Don, via the website“?

Back to practicalities, a chap in the village keeps geese.  I wonder if he’d miss one!  Two birds with one stone;  new pen, and I can only afford spaghetti on toast for Sunday dinner tomorrow.

🙂

Dave

[JasonBModerator @jasonb]

Anyone found the article yet? I’ve not been able to turn it up.

Looking at the various charts posted I notice they have different hole patterns in their plates so may not be ideal for Don if he has different plates to those shown here.

[JasonB]

On JasonB Said:

Anyone found the article yet? I’ve not been able to turn it up.

[…]

I have just enlisted the help of Chat GPT

The response was superficially impressive, but gets us no further

Q. model engineers workshop article on dividing, using a gearbox … please identify and locate

A. ….

Q. Please start searching at issue #1 which was published in 1990

A. ….

 

If anyone is interested in its answers … just repeat my line of questioning

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

I’ve just asked a broader question

Q. engineering article on dividing, using an available gearbox … please identify

… and this is part of its answer:

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.

But Safari considered the linked site unsafe … Grrr!!

MichaelG.

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Update: https://www.homews.co.uk/page425.html?utm_source=chatgpt.com

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