Dividing Head designed by LH Sparey.

[Rob.Wilson]

Hi Lads ,

      I was asked on another thread by Matthew for a few photos of my dividing head  so here goes .

The dividing head was designed by LH Sparey  and the drawings are to be found within his book "The Amateur's Lathe" . This is a cracking book with a wealth of information on operations done in the lathe , milling , screw cutting ,boring to name a few, the book  also has drawings for tooling/attachments for the lathe . The book is Myford based but dont let that put you off as its still relevant what ever  make/model of lathe you have , and I would say its a must for the beginner and I am sure a few old hands would still learn something from it . 

Here is a photo from the book of the dividing head . (dont ask for a clearer photo buy the book LOL)



There are two aluminium castings shown , one for the main body the other for the banjo , dont be put off by this if you have no casting facility ,mine  was made before I got into casting  , I did not even have a mill at the time , so it was all machined on the lathe from bar stock bolted/screwed together .

Photos





The banjo that holds the gears can be swung 360 deg ,to a convenient position for different setups .The moving banjo is also hand for setting the start position of a division .





A few different setups . these are mocked up shots just so you get the idea .

Parallel with lathe axis  bolted to cross slide .



Perpendicular to lathe axis ,bolted to cross slide , bolted directly to the lathe cross slide  puts the dividing head spindle centre height  on the same centre height as the lathe spindle . This is because the main body is bored with a boring bar between centres with the body fixed to the cross slide . 




Now combined with a milling slide there are allot more possibility.









Indexing is done using the lathe change wheels , no need to make index plates .

Simple direct indexing .




Adding  another gear gives more range.



And compounding gives you an even greater range of divisions .




There is room to add more gears if needed .

Rob






Edit ; First photo





 

[mattinker]

Thanks Rob,

it's exactly what I had in mind, with enough room too be able to use more than one gear. I found the book online, about €9 including postage to France, in the UK the postage is free, half of the cost!

Thanks again, Matthew

[Rob.Wilson]

Hi Matthew

9 euros well spent  ,

I find the dividing head very versatile, quick easy to set up  and have used it on the shaper and mill . 


Rob

[dsquire]

Hi Rob

Even back when you made this it has your mark of quality on it. This would be a welcome piece of kit for anyone with a lathe. The only limiting factor that I can see is ones imagination. Well built and well shown. 

Cheers 

Don

[Rob.Wilson]

Thank you Don 


It dose open all sort of possibility if you dont have a milling machine , gear cutting  ect , another good thing is its made with the same spindle nose as the lathe so second operations you can just leave the job in the chuck and mount the chuck straight to the dividing head no loss of position.

The design is adaptable to nearly all lathes as long  as there  is some way of fixing it to the cross slide , weather it be tee slots , a row of tapped holes or using the compound slide spigot .


Rob 

 

[NeoTech]

That could be fixed to a Milling machine table as well i guess. =)

But how do you calculate the gearing for no of indexes? =)

[John Rudd]

Rob, Nice job as ever...

I built the indexer designed by Harold Hall in one of his milling books...Works for me..

But how do you calculate the gearing for no of indexes? =)

Easy...1 degree equals 360 teeth....use a combination of gears that you have...whether it be two, three or four...

Two gears of the same number gives the same output, i.e turn one the other turns the same but in the opposite direction...so ten and twenty would give 2:1 or 1:2 so that would be half or double...

[Rob.Wilson]

Example

Say you need 18 divisions 

45 tooth wheel on the spindle  , indexed every 5 teeth would give 9  so add another gear to give a 2 to 1 ratio and index every 5  on the driver would give 18

  (45x2 )/5 = 18

Rob

[vtsteam]

Very clever tool!  I'm going to have to send for that book. 

[John Rudd]

Example

Say you need 18 divisions 

45 tooth wheel on the spindle  , indexed every 5 teeth would give 9  so add another gear to give a 2 to 1 ratio and index every 5  on the driver would give 18

  (45x2 )/5 = 18

Rob

Aahhh better put than my explanation......... 

[Fergus OMore]

You can get 18 from a 90 tooth not from a 45 which is short of a 2 in the factorisation. That's simple indexing but you can cheat by changing the detent shape to do 18 by effectively using the crests on the 45 tooth gear- to become a 90.

[Rob.Wilson]

Probably not the best example as it would need a 22 1/2 Toothed wheel to get the 2:1 ratio   


Rob

[hopefuldave]

That's a nice bit of kit, Rob - what's the spindle height above the boring table? I'll consider getting the book, but I suspect I'd have to scale it up.a bit, and making a D1-5 spindle for it might be a bit of a challenge

Other than having the right changewheels, is there a way to cut prime/large-factor gears with it, 127 tooth for instance? My current plan involves modding my rotary table to allow rotating the index plate and compound indexing... But I need to do the maths as all the tables I've seen are for 40:1 worm ratio, not mine's 90:1....

[Rob.Wilson]

Hi Dave

I would have to go measure the centre height . its about 1 3/4 on the Myford .

I have not tried to cut large prime number gears with it so cant really say    What I can say it it works fine for all the common divisions most home shop engineers are likely to come across . as long as it not 18 

Rob   

[NeoTech]

Hmm where can one buy this book? Seems like o interesting project for my Aciera mill. Cuz i hate indexing plates and that bloody round table. =)

[Mayhem]

Gee Rob - those slap happy white paint marks are really out of character for you!  Are our standards dragging you down 

[Fergus OMore]

Dave,
          Might I step in?

Sparey's book is excellent. I bought mine as a erk in the RAF way back in 1948. Cost the earth then- but never regretted it- still have it- still use it.
However, George Thomas in Workshop Techniques is 'more advanced' He goes into the real complexities of things like 127 teeth which as we all know- doesn't factorise being a prime number. Martin Cleeve does as well but one guy at a time. GHT described two devices( well, mainly, cos there was more) but he described utilising the use of the bull wheel found on the Myford ML7( which is a bugger of 65) and a more useful one on the Super 7 which is 60tooth. So he made a headstock dividing gear for them ( and the ML10) but he went on to describe a small separate dividing head which started off as a basic machine( like Sparey's) but then took on a set of homemade division plates and then- all singing and dancing- a micro adjustment -to spilt large prime numbers like 127 to do metrics on an imperial machine. Got one- I know.

So GHT gives a set of drawings of his head and which can be scaled up or down- plus how to do things with a one hole division plate- great eh?

So back to cutting metric threads- where you really came in? You can cheat with a say 8TPI leadscrew with either a 21 set of gears, or a 63(nearer) and so on.

If you think about it, if your leadscrew is worn a bit, even fitting a 127 on will give a no better result than the simpler, cheaper gears.  Friend Dennis Chaddock immoral words- and I quote

20 change gears in two gear combinations give 380 combinations whilst they give 29, 070 in a 4 gear and 775,200 in 6 gears  and that( and I haven't checked) gives 804,650 ways

If your leadscrew is somewhat worn- it is rather larger.

Yes?

Norman

[PeterE]

From the discussion it sounds like the Sparey design is earlier than the GHT design. This I think explains why the GHT design takes things a bit further,

Looking at the "basic" machine, I think there are very few differences between the two designs. The difference comes with the GHT additions where he managed to solve quite a few of the dividing complexities.

At the end of GHTs book "Workshop Techniques" there are also sketches/drawings to make patterns for those that want to cast their own dividing head.

Rob, your version looks very smart and handy. Well executed! 

Grmpffm my ToDo-list just gets longer .... 

/Peter

[mattinker]

Hmm where can one buy this book? Seems like o interesting project for my Aciera mill. Cuz i hate indexing plates and that bloody round table. =)

NeoTech

I googled "Dividing Head LH Sparey" and ordered a copy, $12.75 shipped to France, from http://www.abebooks.com.

Norman,

I wasn't looking for advanced stuff, I have a dividing head that I made from a worm drive from a conveyor belt, inspired by the Gingery dividing head. I need something simple to graduate dials and stuff.

I'm could make the dividing head from the photos, but I bought the book anyway!

Regards, Matthew

[Fergus OMore]

Matthew,
 Apologies but others were asking supplementary questions which perhaps prompted some expansion of   your original topic.  I missed the original thread being deeply involved in a ball and socket joint- that went wrong- and is still ongoing.
Or not going!

Felicitations

N

[Rob.Wilson]

Gee Rob - those slap happy white paint marks are really out of character for you!  Are our standards dragging you down 

    Nowt wrong with slapping a bit paint pen on things   

Thanks Peter . 

The difference in the two dividing heads is the Sparey one  was designed to be used on the lathe , back in the day when the only machine available to the amateur was a lathe . 


Rob

Edit    The GHT dividing head is also designed to be used on the lathe ,,,,,,,,got mixed up with  the Harold Hall dividing  head 

[hopefuldave]

Dave,
          Might I step in?

So back to cutting metric threads- where you really came in? You can cheat with a say 8TPI leadscrew with either a 21 set of gears, or a 63(nearer) and so on.

If you think about it, if your leadscrew is worn a bit, even fitting a 127 on will give a no better result than the simpler, cheaper gears.  Friend Dennis Chaddock immoral words- and I quote

20 change gears in two gear combinations give 380 combinations whilst they give 29, 070 in a 4 gear and 775,200 in 6 gears  and that( and I haven't checked) gives 804,650 ways

If your leadscrew is somewhat worn- it is rather larger.

Yes?

Norman

Thanks, Norman,

Metric threading isn't the end in mind, I already have that (flip a lever on the QCGB, swap two gears, a minute or so?), but I have ideas for dual inch/metric dials and they involve cutting a few 127 tooth internal gears.....

[hopefuldave]

Thanks, Rob, sounds like I'd have to scale it up to double size!

At a pinch I could use the 127 tooth metric translation gear from my lathe but it'd be good to have the facility to make other prime-number divisions - it looks like I'm going to have to brush up on the maths involved in compound indexing..... The 127 gear's also a touch over 8" diameter, not exactly easy to attach!

The George Thomas VDH would be ideal, but attaching it would be tricky with an enclosed headstock and a 70-tooth headstock gear would leave me with a lot of calculation to do (and need a DP pitch worm made, for which I'd need to cut some changewheels...). I have a spare 90:1 worm and wheel that I could build around, so that could hang off the banjo on the Sparey design?

[Fergus OMore]

Ooops, lost in the translation. Silly me!

Thomas produced two dividing heads. The VDH is perhaps going to be trickie but he produced the small dividing head which is- as rightly explained by others- a casting which ( actually two castings) which goes on the saddle/vertical slide or elsewhere.
What you get is a sort of refined Sparey but in its basic form, the ability to direct index using the large gear but also there is provision for a worm wheel to take division plates but a second worm wheel to obtain other divisions.
However, the head will also go the milling machine with a homemade tailstock casting or be supported integrally in a similar way as on the Quorn. It gets a wee bit cleverer than that because Dr W A  Bennett saw that the Thomas Universal Pillar Tool comes into play by a modification by Jim Batchelor move the pillar tool onto the lathe saddle- to drill and also rivet and stake.

What has to mentioned is that many of the parts of the Headstock attachment interchange with the Small Versatile Dividing Head which interchanges with the Universal Pillar Tool which becomes a drilling machine- on the lathe etc.

Now this is all very simple stuff because the lady with the problem of the ball and socket joint  and Bill Bennett celebrated their 50th Year graduation as dentists last June- whilst the Olympic Torch was being wafted about on the model of the Sydney Harbour Bridge in Newcastle.

Now I married the ball and socket lady- and tried to coerce Bill into doing the rest of the Martin Cleeve articles that he did on the Thomas stuff. Not all at the same time- of course

Now it gets complicated after that.

I'll stop at that- I have the grass to cut.

[PeterE]

Dave,

You could fit a gear of your choice to a mandrel secured in the back end of the spindle, and then fit the dividing worm and plates as needed on a carrier to fit your lathe.

That is how the GHT dividing attachment was fitted to the 254 lathe.

BR

/Peter

<edit> One-hand editing etc, etc ...  </edit>