dividing head /indexing

Mark,

Here's another one [by Tony Jeffree] that might provide some inspiration: **LINK**

http://www.jeffree.co.uk/pages/divheadmk2.html

MichaelG.

A bit large there is a thing called a Spindex that does 1 degree increments as standard. Over on HSM forum someone did a conversion to add a worm wheel.
Your earlier questions: Not often seen big tailstocks on ebay - you need to look for a 12 in lathe being broken for parts which is less common.

When a worm is used on an 'ordinary' gear the axis of the worm has to be canted over - you will see this in some pictures.

....ideally by the helix angle of the worm at the pitch circle diameter. The contact area between a worm and a spur gear, or helical gear of matching helix angle, is a point, so not ideal.

Andrew

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Not 'properly' but probably 'adequately for the job' ... provided that you angle the worm to match the helix angle of the thread.

MichaelG.

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[beaten to it]

Edited By Michael Gilligan on 14/11/2016 20:59:53

Mark, those gearboxes are plentiful in the UK, that was just a quick search. On mine I fitted a large flanged shaft and then bolted an ER 32 face plate collet chuck to it. That gives me from 2mm to 20mm but I could have fitted a 3 or 4 jaw chuck if I'd have wanted.

Hi Mark

"Alan, very nice and simple ,is the spindle just floating in the steel body ?"

It is not floating the spindle runs on a 10 degree tapered bronze bush at the front and a plain parallel one at the back with adjustment to eliminate end float. As to the mesh with the spur gear, it seems quite good enough and has seen plenty of use but shows little wear.

Alan

As Michael posted earlier, I'm (slowly) making a fabricated version of the GH Thomas dividing head. For worms and worm wheels, I have used a spare Myford 60T x 20DP change gear for the main worm gear. The worm was turned up on the lathe. By thinning the teeth on the worm slightly, the worm does not have to be offset by the angle of the helix. It runs straight in line. I think I picked this trick up from Martin Cleeve's book on screw cutting in the lathe. It works well so far.

For the secondary worm and wheel on the GHT design, I used the 60T Myford wheel with a plunger on the teeth to direct index the smaller 60T wormgear - so the GHT dividing head's first use is to make its own second gear!. Using a 32DP gear cutter from RDG, I kicked the vertical slide around by 4.2 degrees so the teeth are not a true helical gear but rather a straight cut gear cut at an angle, so to speak. With an Acme thread worm turned on the lathe it meshes straight on with no thinning of the thread needed in this case.

GHT's design is fiddlier to make than many other designs but has that classic look that matches my vintage lathe, and the nice but rarely likely to be used ability to divide accurately any number of divisions, including prime numbers, to a resolution of 1/1000th of a degree. Bit of a giggle really, but it does allow you to make your own extremely accurate indexing discs (or plates) using the dividing head itself and that secondary worm and wheel along with an indexing disc with one hole only.

So much fun, how could your resist? And so far the cost has been limited to a few offcuts from the local steel supplier and one 32DP gear cutter. The rest came out of the scrap box.

It's late right now but I will upload some pics of the latest progress to the What I Did Today thread tomorrow.

Here's a couple of older ones showing the Myford gear used as main worm wheel, and the worm that meshes straight with it by thinning down the thread.

Edited By Hopper on 15/11/2016 12:24:47

Edited By Hopper on 15/11/2016 12:27:00

Edited By Hopper on 15/11/2016 12:28:46

On a similar note, over on Youtube, Stefan Gotteswinter has just posted a video teardown of a Chinese 5C indexer.

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Thanks for picking-up the story, Hopper

Being without welding facilities; I keep casting my eye over various pipe-fittings and scaffold-clamps ...

MichaelG.

Muzzer,

Great video; thanks for the link.

MichaelG.

Blimey, free WiFi in business class as well?

Andrew

Hopper , that looks very nice ,i unfortunately dont have a welding set to make up a main body like you`ve done . Seems a very good way to make up something from lots offcuts.

Im confused by what is meant by secondary worm and wheel???

As this is 2016, I suggest you consider using a stepper motor to drive the worm driven by one of Mike (?) Ward's excellent controllers. Then you don't need to worry about division plates, prime factors, and all that stuff, just type in how many divisions you want and away you go. JS' approach using a commercial gearbox would be quick. I have converted a Myford DH and wouldn't consider going back to plates'n'oles.

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This should make it reasonably clear, Mark **LINK**

http://metal.duncanamps.com/projects/hemingway/hk1500_vdh.php

Scroll down to 'Simple Indexing' and 'Micro Attachment' if you're in a hurry.

MichaelG.

Edited By Michael Gilligan on 15/11/2016 16:48:31

Posted by Michael Gilligan on 15/11/2016 14:25:03:

Being without welding facilities;

MichaelG.

silver solder would be adequate.....

Posted by Bazyle on 15/11/2016 18:13:12:

Posted by Michael Gilligan on 15/11/2016 14:25:03:

Being without welding facilities;

MichaelG.

silver solder would be adequate.....

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Indeed it would ... Which is why I'm casting an eye over things that might constitute big-ish 'ready-made' portions.

I'm in no rush; but I do fancy making something roughly the size of a GHT VDH, configured to take W20 collets.

MichaelG.

I had thought about using a large diesel engine piston bolted down to a flat base plate. The gudgeon pin hole would be nicely honed and nice and straight and square, ideal for puropse. But attaching all the bits and pieces to a round aluminium piston could be a bit challenging.

Or you could carve the whole thing from a piece of 4" square steel bar about 5" long. Or a suitable square block of steel or cast iron bolted and dowelled to a flat baseplate would do well too. I don't have such large lumps available where I live here out back of the Outback, and shipping costs are prohibitive so I went with what was available locally, 1-5/8" round bar and a  bit of 3/8 plate.

My welding facilities are very basic and affordable: an ancient AC welder picked up at a garage sale for $50, including a 5kg packet of rods I am still working my through. Worth its weight in gold. They don't give as pretty a weld as the newer DC welders (especially in my shaky hands) but they run forever and get the job done.

Edited By Hopper on 15/11/2016 22:57:54

Edited By Hopper on 15/11/2016 23:06:42

Hi Mark,
I've long thought your own suggestion of a lathe headstock would provide the basis of a robust and capable dividing head.
A quick look on ebay and this Myford ML8 headstock came up. It's less than ideal in that it's from - dare I say it? - a WOOD lathe... but it's well built and has a centre height of 4" (though that starts from the top of the through hole rather than the base).
Some interesting (challenging?) fettling could make something of it. Two of them are for sale now for less than £50 each. And no - it's not me that's selling them...

The spindle is a bit small with only MT1. But it comes with a built in 24-hole indexing function!

The tailstock is also for sale...

Steve

Hi Steve , i noticed them yesterday, i also found someone else selling just the casting minus the door on top for £12 +delivery , the same seller wanted double the price for the little cover door on top.

Problem is im trying to make on the cheap and if i start buying all sorts of bit the price starts mounting.

How about using a discarded car cylinder head? One with a single overhead cam will have the camshaft bearing caps machined into the head casting, dead square to the head gasket surface that it sits on. You could cut one cylinder's worth of the head off with a hacksaw (aluminium head of course!) It clamps to the table, or a baseplate using the head bolt holes. Turn up a spindle to fit the camshaft bearings, put a chuck on one end and a 60T Myford change gear on the other. Bolt on a mounting bracket for a worm wheel turned up to match the Myford gear. (Details of this are available in GH Thomas and Martin Cleeve's books re exact pitch for 20DP worm and even the change gear train to cut it.) All you have to do then is make the indexing plates with all the holes in them. If you have a rotary table already, that will be easy.

I have a mate who is building a whole milling machine using a couple of car engine blocks and heads for the main components, so should work for a dividing head.

Here is the type of head I am thinking of:

Or even a single cylinder motorcycle cylinder head? Available for those Chinese made Honda clones on the net stupid cheap.  Pull out the camshaft and turn up a spindle to suit.

Edited By Hopper on 16/11/2016 11:29:39