Help with dividing plates

I am looking for a 60 hole 5.5 inch dividing plate to go on the tail end of my lathe spindle - that was the original design and it seems a useful
accessory worth recreating. When I look for ones for sale I see them with weird numbers of holes, 47, 41, 37. Perfect if you want 47 equally spaced holes. I am mystified why you don't see 60 hole ones, it strikes me as a much more useful number.
Regardless of my confusion about the usefulness of strange numbers of holes, does anyone know where I can such a plate, or even a blank for someone else to make one for me? I am thinking I may have to resort to making a blank from a chuck backplate casting.
Steve
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On Sun, 21 May 2006 15:26:51 +0100, "Steve Richardson"

These are used for compound or differential dividing heads. Lots of times a plate has prime numbers of holes. For indexing as you're describing, even numbers would be more common. There's a number of articles around for laying out and making your own indexing and dividing head plates using pencil and paper to do the layout. Google it.
Below, I've included a selection from http://primes.utm.edu
The First 1,000 Primes (the 1,000th is 7919) For more information on primes see http://primes.utm.edu /
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 101 103 107 109 113 127 131 137 139 149 151 157 163 167 173
Regards,
Pete Keillor
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On Sun, 21 May 2006 15:26:51 +0100, "Steve Richardson"

Most dividing heads have a gear ratio that is an even integer (e.g. 40, 90) so, if one wanted 60 divisions one would need:
40/60 = 2/3 turn
which could be accomplished by:
10 holes on 15 hole plate or 12 holes on 18 hole plate or 14 holes on 21 hole plate or 18 holes on 27 hole plate or 22 holes on 33 hole plate or 26 holes on 39 hole plate
or:
90/60 = 1.5 turns
1 full turns of crank and 8 holes on 16 hole plate or 9 holes on 18 hole plate or 10 holes on 20 hole plate
As a consequence, there's no need for for plates with large even numbers of holes.
Regards, Marv
Home Shop Freeware - Tools for People Who Build Things http://www.myvirtualnetwork.com/mklotz
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Several years ago, I made a George Thomas Versatile Dividing Head from a Hemingway kit. The guidance in GHT's book "Dividing and Graduating" was excellent, showing you how to make a 60-hole plate using the supplied 60:1 worm/gear, and all the other sets of divisions from this using the fine feed. I certainly recommend getting hold of the book, even if you are making a different design.
David
--
David Littlewood

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David, Dividing and Graduating is no longer published ! It was combined into Workshop Techniques which includes the Universal Pillar Tool.
I agree with what has been said- having got the Small Dividing Head and the plates generated by Thomas's words and music.
Hope this helps a bit
Norman
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Ah, sorry, I forgot that. His books must be among the very best home workshop manuals ever published. At least, if anyone knows of better ones I'd be very interested to see them!
David
--
David Littlewood

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David, I agree about the " guru" but I include Kenneth C Hart or " Martin Cleeve" who, if one really reads him explains the transposing gears of 127 in his many forays into " Model Engineer" and later in his" Screwcutting in the Lathe".Here was a guy who couldn't afford a whole Myford ML7, then was made redundant and made a very fancy loving making nuts and bolts on it. Again, there is Jack Radford, the New Zealander, who kept forgetting in his description to add an important bit in the description. Yes, Steve, that makes four. Then there is Professor Dennis Chaddock who frustrated the rest of us in his creation of the "Quorn". Rather too much for most intellectuals! Most castings are still on shelves- or worse. You do need the ability to transfer washers from one pocket to another. Essential in dividing! Finally, there is " Tubal Cain" or Tom Walshaw who created two pillars of brass in the desert and had problems with one of his Myfords slipping down on out of alignment on a Lakeland Fell.
Now then, as JAR would say. Oh, I am not an engineer! heavens, no!
True,I studied Tractenberg maths and studied Pelmanism. Of the latter, I would write the name down in case it skips the memory.
My kindest regards to one and all
Norman
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Pete Keillor wrote:

A 60 tooth gear can be useful here. There are a couple of designs around for detents, but I'm sure you can design your own.

Something I do quite a a lot for marking up sheet metal is to draw the design on computer first, print it out, and stick the printout to the metal.
Drawing doesn't take long once you have the knack of using your choice of drawing program, in fact it's much quicker than scribing lines, and it is very easy to make it accurate. Absolutely accurate. Yike!
Snap-to-grid is useful here. Rectangles with zero height or width make easy vertical / horizontal lines. Use the rotate tool to get accurate angles.
I use a very cheap (on sale for 19.99 in some Tesco's, and often to be found for 25 elsewhere) Lexmark Z615 printer, using which the whole process is accurate to better than 0.1mm/4 thou over an A4 sheet of paper in both X and Y axis-es. axes?
A tip, tell your computer that there is no colour cartridge installed and the Lexmark will print in B+W, automatically converting any colour designs to B+W.
You then have a full-scale paper model in your hands to check fit, if the design is sensible, and so on. You can cut it out with scissors to see if it will fit through that gap, glue it to cardboard and cut with scissors/scalpel to make a stiff 3-D model, and so on - then just print another when you are satisfied.
I use 3M removable spray mount adhesive (available from any art materials shop and many stationers) to stick it to the metal. Water-based glues distort the paper. Center pop or spot, then drill/cut/machine, the paper peels off easily afterwards.
And if needed half-way through you can always amend, print another copy, and align it with any convenient cut edges or holes. Or just print another copy for making a second or third part.
Or send the design straight to the laser cutting people :)
--
Peter Fairbrother


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The Classical way is to follow the construction articles by Professor Thom and how the Megalithic Yard etc were constructed. A lot cheaper than going to Tesco's- if we are saving money. This system is far more romantic than lasers but it still uses rays and has for 4500 years! Might even improve improve your sex life! Ahem!
Norman
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I think you guys are missing the point. If I thought I could accurately drill holes by marking up and then free-hand drilling, then why would I want an indexing plate ?
It strikes me that marking 60 holers and accurately drilling them is the sort of repetition that is best done by a machine, i.e. one that already has this facility, be it mill. drill, or lathe.
As for links to Universities studying to find the ultimate prime number - polite words fail me...
Steve
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Come, come Steve! I started with 4500 years ago and all one needed was a few sticks, a bit of cord and a bloody big stone. What could be simpler or cheaper?
For those developing the theme, I simply corrected a more modern source. Moreover, I simply re-affirmed David's suggestion of recalling the Gospel of George H Thomas, the Divine.
Incidentally, the editor of the book in question didn't do a degree in maths but in - dentistry.
Cheers
Norman
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And I did a degree in metallurgy - which they say is the second oldest profession - and you can't get a degree in the older one, though you can be a professional.
I don't know what I did to trigger this diversion, I thought I asked a perfectly sensible question about dividing plates, next thing its taken-on a life of its own and gone barelling down some odd paths as far as Stonehenge - I think that what did it was the mention of 47, or maybe it was just the end of a wet weekend - maybe everyone has been holed-up in the pub all afternoon.
So does the fact you need a 127 tooth gear to cut metric threads on an imperial lathe have some sort of deep mystical meaning to maths people ? I suppose someone has written a book on that too! To me its just simple arithmetic - and you mustn't confuse arithmetic with maths, eh !
Steve
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On Sun, 21 May 2006 23:19:26 +0100, "Steve Richardson"
I thought the answer was 42 :-)
Jim.
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wrote:

How many roads must a man walk down ...
Steve
You know if life begins at 40 I must be going through puberty again - which could explian a lot!
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>So does the fact you need a 127 tooth gear to cut metric threads on an >imperial lathe ...
You don't.
--
Charles Lamont

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On Mon, 22 May 2006 09:53:38 +0100, Charles Lamont

Weeelllllll........ Practically you don't, technically you do.
127 is the lowest number [ 254 / 2 ] that is mathematically correct
There are many combinations that are very close and are only a few parts out in 1,000's
As no one ever knows to what tolerances / errors their leadscrew is cut to the chances are that the errors are greater than the difference in the change wheels.
The purists will say that you need 127 but unless you are cutting a new thread for your 0 - 25mm micrometer then it's moot point.
.
-- Regards,
John Stevenson Nottingham, England.
Visit the new Model Engineering adverts page at:- http://www.homeworkshop.org.uk /
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On Mon, 22 May 2006 12:16:46 +0100, David Littlewood
snip

A 127 tooth setup uses the 127 tooth wheel as a driven gear
In a 21 or 63 tooth setup the wheel should used as a DRIVER gear
63:160 = 1:2.5396825 which is an error of on only 0.001" in 8".
A 1:2 or 1:4 preceeding ratio drops the 160 component to a more manageable 80 or 40 teeth.
Jim
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Well, Steve?
My metric quadrant on the Myford Super 7 B contains the following 60T, 52T, 44T (pinned to the 52), and another 60T idler.
In my bag of swag for the 7, I have a pair of 21s!
Not Pelmanism, I took the cover off the gear box!
Oh, and if my Pelmanism is working, Cleeve flogged the 127 20DP problem in 1953. Give or take a couple of tides in Hong Kong Harbour- as usual. Change of Diametrical Pitch?
Norman
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I am advised that it all started in Volume 113 in 1956 ( cataracts???) The 127 gear mentioned by Cleeve was 30DP.
Well, Steve?
Norman
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ravensworth2674 wrote:

Methinks you have a tendency to pontificate, Norman, albeit in a waffling sort of way. What's a 127t 30 DP gear, Vol 113 and Cleeve etc got to do with the subject in hand? If it took this character Cleeve until 1956 to discover the use of a 127t gear, perhaps he was smoking a similar substance to yourself. BTW Hardinge (Cataract lathes) had long since sorted the the scenario.
Tom
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