How to get 89 divisions from a dividing head

[Neil WyattModerator @neilwyatt]

Sorry Adam,

Just trying to demonstrate that because a dividing head can offer apparently stunning levels of precision, in the real world you can often get away with simpler solutions.

A 60-tooth worm gear with a 60-division plate will give you 3600 steps, or 0.1 degree precision. For a 4 inch diameter that's 3-thou steps. As my stuff is usually less than 2" diameter I'm happy to work to the nearest 0.1 of a degree and forego division plates.

Neil.

[John Stevenson 1Participant @johnstevenson1]

Heretic……………………………….

[BazyleParticipant @bazyle]

I have what I think is a JS plate that is only 5 1/2 in dia but has a ring of 127 holes. they are so close together I don't think 128 would fit.

I'm sure people woud like you to start doing them again John, though I got a set of 3 'second hand'.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 19/03/2015 20:40:10:

… I'm happy to work to the nearest 0.1 of a degree and forego division plates.

.

So, I presume you won't be making the RA drive for your telescope mount.

MichaelG.

[John Stevenson 1Participant @johnstevenson1]

Bazyle.

I will be starting to do plates again later in the year plus some other bits. The tooling supplies went to pieces after Gert died. Although I did all the bits it was left to her to do the selling on Ebay and some on the ME Tools website, the packing and dispatch.

I find making it is fine but the packing and dispatch takes far longer than most realise. I have also come to the conclusion that Ebay is a waste of time for selling unless you are a power seller or have a shop, which does cost you.

So when I get sorted and back up running I just propose to reopen the web site which is still there, you just can't buy from it at the moment. Stock as regards materials is there, I had over 500 division plates laser cut just prior to Gerts death just to get a decent price and there are well over 100 Bridgeport drawbars still bundled up as received from the heat treat shop well over a year ago.

[Anonymous]

Adam: Here's a picture of my dividing head:

Bottom left you can see the gear on the table leadscrew ready for spiral milling; although I have not needed to use the facility thus far.

I bought my dividing head from a chap in Long Eaton. What was his name, oh yes, I think it was JohnS?

Andrew

[John HinkleyParticipant @johnhinkley26699]

I appreciate that you've probably had your problem solved by taking up John S's offer, but here's my take on it.

While playing around with a program called GearDXF, which I mentioned in another thread, I changed the gear parameters to 89 teeth, Mod 1. Overall diameter is 9.1cm. This gave the output below, albeit in dxf format. Is this the sort of thing you could have laser cut and attach to your dividing head? If it's already what John S. has suggested, I apologise for the duplication, I obviously misunderstood John's offer!

Regards,

John H.

[CotswoldsPhilParticipant @cotswoldsphil]

I'm waiting for a delivery from ArcEuro so have time to burn!

I'm finding this thread quite informative as I've never done any indexing above the number of spokes on my Minnie's wheels – so far.

A method I remember from ME many years ago (using readily available components) is to wrap a length of bandsaw blade with the appropriate number of teeth, around a disk of plywood, it would be MDF today, and index on the teeth. Clearly getting the joint/overlap accurate is important but perfectly do-able. Improved accuracy could be achieved by using multiples of the required final number and indexing accordingly. Also, would it be possible to starting indexing between 90deg and 270deg (the joint being at 0deg) and then resetting for the second half so as to avoid the overlap?

Regards

Phil

[John Stevenson 1Participant @johnstevenson1]

Here's one [ or two ] I did earlier.

The one on the right is the "get Adam out the mire " plate and has 127, 89, 63 and 25 holes on it to cover the 89 he needs and others that are not on standard plates.

The one on the left id the Elliot No #1 plate which Adam doesn't have, he only has the No #2 plate, so at a later date he'll have chance to make one of these up.

Now need to find a stamp which is harder than doing a plate

[Michael GilliganParticipant @michaelgilligan61133]

Posted by CotswoldsPhil on 20/03/2015 11:35:03:

A method I remember from ME many years ago (using readily available components) is to wrap a length of bandsaw blade with the appropriate number of teeth, around a disk of plywood, it would be MDF today, and index on the teeth.

.

Phil,

An excellent [and potentially less bloody] alternative is to use 35mm film, and index on the sprocket holes.

I also wonder about using 'timing belts' …

MichaelG.

[Adam HarrisParticipant @adamharris13683]

Andrew, I actually have the Victoria precursor to yours that is slightly different and is set up the opposite way around (dividing plates are on the opposite side). What are your levers on the dividing head facing us? Mine actually fits perfectly on the middle T slot of the Tom Senior M1 but can only be used in gear cutting format as it is far too tall for the space under the milling spindle when swivelled 90 deg to use as a horizontal rotary table. It has a whopping 7.5" chuck that is far too big so I am putting in a Myford nose on an MT3 spindle , through a MT4-MT3 sleeve, with a drawbar but again sadly there is no space (when swivelled 90 deg vertically) between the base and the end of the drawbar hole to fit a drawbar in that position. Horizontal is no problem.

Do you know, out of interest, what the nose thread is on these?

[Adam HarrisParticipant @adamharris13683]

John, Thank you so much. I have sent you a PM. Adam

[Neil WyattModerator @neilwyatt]

> So, I presume you won't be making the RA drive for your telescope mount.

the worm wheels are already part of the scope's equatorial mount, so any error will be divided by another 100, I suspect that 0.001 degree accuracy would be enough for me – but I will be using scavenged nylon gears anyway.

Neil

[BazyleParticipant @bazyle]

Andrew's dividing head is unusual as it is right hand, most seem to be the other way round. K&T made a point of making them the other way round to put on the RHS of the mill for right handed people and they put the gear on the RHS end of their mills.
What most MEs need is the Elliott 3 1/2 inch head with MT3 spindle which is more in 'our' size. Oddly when on ebay they don't get much interest.

For the ideas that talked about printing a paper circle of holes one could always 'borrow' your workshop clock. By manually moving the minute hand around you can use the hour hand to divide the circle into 60×60 points. A spreadsheet would tell you the 'times' to set to indicate the holes required. Using 'time' would be much easier to understand than counting.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 20/03/2015 13:00:36:

… the worm wheels are already part of the scope's equatorial mount

.

Ah … My mis-understanding … I thought you were making the whole head.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Bazyle on 20/03/2015 13:35:26:

… one could always 'borrow' your workshop clock. By manually moving the minute hand around you can use the hour hand to divide the circle into 60×60 points. A spreadsheet would tell you the 'times' to set to indicate the holes required. Using 'time' would be much easier to understand than counting.

.

Some chap called Michael Gilligan proposed that method, years ago, in an article in Model Engineer.

MichaelG.

.

Found it:

1993, Vol.171, issue 3951

 

Edited By Michael Gilligan on 20/03/2015 14:16:56

[Adam HarrisParticipant @adamharris13683]

Bazyle, do you know the spindle thread on the Elliott 5" Universal Dividing Head and if it is a standard thread that is shared by any particular lathe manufacturers? It would make it easier for me to find a home for the chuck…it looks like a well made chuck although there is no name on it.

[Anonymous]

Yes, bit of a bummer that the dividing head is right hand; especially as I'm left handed. It hasn't really proved to be much of a problem so far though. If I really wanted to I could swap the dividing head to the other end of the table and reverse the milling spindle. However, I think it would be difficult to swap the gear the spiral milling.

The small lever to the right is an (ineffective) spindle lock. The lever and gubbins with the curved slot engages, or disengages, the worm from the spindle and allows the mesh to adjusted. In the position shown the worm is disengaged, as the job I've just finished was to cut four flutes into some home made taps before hardening and grindng. I just used direct indexing using the slotted disk behind the chuck for that.

According to my manual the spindle nose thread is 2" 10tpi UNS, although I haven't confirmed that by measurement.

Andrew

[Adam HarrisParticipant @adamharris13683]

Thanks Andrew. Do you know if that thread is used by any large lathe manufacturers? I was thinking of a home for the 7.5" chuck….

[BazyleParticipant @bazyle]

Adam, sorry mine's the smaller head and its thread is not used on a common lathe as far as I can tell. (foolishly I didn't bid enough on a 5 inch one with original differential gears) Possibly deliberate so yours is likely to be different too. However you want to keep the chuck a) for when you sell the head, b) for when you do make something big, c) so you can use the backplate as a catch plate and d) for a smaller chuck that hasn't lost its outside jaws

Of course a left hand psition is better for most milling so you can feed away from it in the traditional but not mandatory direction.

[John Stevenson 1Participant @johnstevenson1]

3 1/2" and 4" centre hight heads have 1 1/2" x 10 UNS and MT3 spindle bore

5" and 6" centre hight heads have 2" x 10 UNS and MT4 spindle bore

[Adam HarrisParticipant @adamharris13683]

John is that 2" x 10 UNS a thread used by any of the main lathe makers, or is it rather unique to Victoria/Elliott?

[Nigel McBurney 1Participant @nigelmcburney1]

I never understood why dividing heads were made either right of left handed, I first used a dividing head on a Victoria universal mill and that was mounted onto the left of the table and thats always seemed the most convenient way,after all lathes have the headstock to the left of the bed. Cincinnati mills mounted their heads on the right,and they must have been made in their thousands, their main competitor was probably Browne and Sharpe and who I believe were the first to make the dividing head as we know it ,mounted on the left so there may have been patent problems at the time forcing competition to have a different mounting position,. Also I have wondered why dividing head spindle have screw threads ,milling in the "wrong"direction can loosen the chuck,particularly when left hand spiral milling. My Hofmann universal dividing head has a tapered spigot and three tapped holes so that the chuck and driving plate are rigidly bolted to the spindle, the spindle is also tapered for centres and tapered mandrels. The photo of the mill with l/h div head mounted on the right is asking for trouble,you need the dividing plate facing the operator. Regarding a horizontal mill with vertical head not having enough space for the div head to be set vertical, set the vertical head at 90 degrees, with the dividing positioned at the end of the table,this gives more room, lack of height was the reason why I sold my Tom Senior and bought an Elliot milmor with 18 inches from table to spindle.

[Anonymous]

Posted by Nigel McBurney 1 on 20/03/2015 20:04:59:

The photo of the mill with l/h div head mounted on the right is asking for trouble,you need the dividing plate facing the operator.

Possibly for you, but although it looks odd I haven't really found it a problem. Because I am left handed it is quite natural for me to lean round and operate the dividing plate with my left hand. And although it is not shown in the picture just to the left is a shelf where I keep a piece of paper on which I keep a check of the number of indexes. Again convenient for my left hand.

I'm not sure I follow the comment on feeding away from the dividing head? I always feed towards it, so that the bulk of the dividing head and its bearing surfaces take the thrust of the cutter. On my horizontal mill I normally cut from right to left.

I am not aware of any lathes that use 2" 10 tpi UNS, it would be quite limiting on spindle bore for any reasonable size lathe. There would also be a potential problem with reversing the spindle. I'm not sure when threaded spindle noses when out of fashion in industry but I suspect it was before WW2?

Andrew

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