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Dividing Head

What is a dividing head

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John Exley20/02/2011 12:35:28
10 forum posts
Being brand new to ME I often hear the phrase dividing head used and I wondered what one was,what does it do,what does it look like and how is it attached to a lathe and how is it used.
 
regards John
Mogens Kilde20/02/2011 13:02:59
60 forum posts
25 photos
Hi John
 
I think a google on the word "Dividing head" is the best way to explain the look and use of such tool - try it.
 
Mogens
Chris Crosskey23/02/2011 14:19:55
15 forum posts
Generally it's a device that allows for accurate control of the rotation of a work piece and its fixing at any point (subject to teh coarsness of the divisions available) in said rotation.
 
There are two sorts (and a third is an extension of the second)
 
Simple dividing heads consist of a a shaft onto which the workpiece can be fixed with an indexing system (normally a multiple of 12, 60 is popular) that allows you to rotate the wrokpiece to any known indexing division and lock it there.
 
Complex dividing heads generally use a worm and wheel to control the shaft and allow for much finer control (and many more divisons). You will find designs for COmplex heads that use trains of spur gears to achieve a similar effect or even put the spur chain on the end of the worm to allow for uber-fine control.
 
Compound dividing heads are basically complex ones with the addition of an extra shaft that can be powered from a gear train off a milling machines table feed. This arrangement allows for spiral milling of slots etc.
 
I would suggest a model engineer probably needs soemthing to do divisional indexing on and although they will rarely need the full ability of a complex head, let alone a compound one. THere are plenty of designs out there for simple heads and some of them are also designed to be extended into complex ones with addition of the worm,
 
THings to looki at if you're interested are the Hemingway Kits version of the GH Thomas Versatile Dividing head, you can make that up in stages, also look at the RDG dividing head as it represents decent value for money. On another tack slightly you could also look at Chronos (and others) who do a rotary table that can have a Myford nose attached and a dividing kit added.
 
chrisc
Nicholas Farr23/02/2011 18:20:41
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3988 forum posts
1799 photos
Hi John, a lot of rotary tables can be used as a dividing head with an optional accessary kit.
 
The picture below shows my 6" Vertex with a four jaw chuck fixed to my cheap drill press on the hurry up, to drill five holes in an oil pump spocket mod, which failed on my car last year. There was not much room for error to achieve the strongest job, hench the choice for this application. I hasten to add this was just to get the engine going again to asses if there was any other failings in the engine.
 
 
Regards Nick.

Edited By Nicholas Farr on 23/02/2011 18:21:40

Wolfie23/02/2011 21:34:34
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502 forum posts
My problem with these things (as another beginner) that I can't find one that even remotely fits my minature lathe
John Olsen24/02/2011 09:35:38
1294 forum posts
108 photos
1 articles
Hi Wolfie,
Unimat did one, and may still do, for the Unimat 3. This is a pretty basic direct dividing attachment, came with one plate and there were three more optional plates. (24, 30, 36 and 40 I think) It is basicly a block of metal with a spindle set in it that has the chuck mounting nose on it. A dividing plate with holes around the edge goes on it, and a spring loaded pin engages with the hole. Pretty simple, not too hard to make apart from finding someone who will drill the plates for you. This sort of things is fine for the general run of things like setting out holes in cylinder covers, machining flats for a large nut, and so on. It would be a bit limiting if you were into clocks, since you need a plate with the right number of holes (0r a multiple) , and being quite small you can't have a plate with lots of holes very easily.
 
regards
John
 
 
John Exley24/02/2011 10:27:53
10 forum posts
Many thanks for all your help lads I have a clearer idea now and will have a look round for one that suits
 
Regards John
Keith Long24/02/2011 20:32:10
883 forum posts
11 photos

John

Rather than looking for a dividing head that you think might do what you want at some time in the future, get a copy of "Dividing" by Harold Hall. It's no 37 in the Workshop Practice Series.

It explains what dividing is all about, has photos of several commercially available heads as well as details of how to make simple dividing heads, that use lathe change wheels for the division. If you don't want to copy Harold's designs at least you'll have much better idea of what you do want and how to achieve some results at a much lower cost than buying a head. 

The time to splash to on a commercially made head is when you really know what you want to do and can't see any way of doing it with what you've got.

Keith

Edited By Keith Long on 24/02/2011 20:33:20

Terryd24/02/2011 21:34:45
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1946 forum posts
179 photos
Hi Keith,
 
I must say that I wholeheartedly agree with your analysis. There are many ways of providing dividing facilities without expending hundreds of pounds on equipment that will only be rarely used. I myself looked at building a simple rotary table with the addition of a cheap worm and wheel from College Engineering Supplies and a couple of home made dividing plates. With a geared head they don't have to be very accurately made.
 
Best regards,
 
Terry
Gray6224/02/2011 21:56:06
1058 forum posts
16 photos
For a Mini Lathe setup, I would seriously consider the small dividing head from RDG Tools. This is based on the GHT dividing head and is very reasonably priced. I built one of these some years ago using the Hemingway kit and have found it extremely useful and versatile. I still use it today on my larger machines. It is a robust and well engineered design.
John Exley25/02/2011 10:16:11
10 forum posts
Many thanks for your replies having looked at the ones available they are expensive I like your idea Keith and will look at the book on dividing.
 
regards John

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