By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Allendale Jan 24th

Unidentified dividing head help please

Could it be GH Thomas?

All Topics | Latest Posts

Search for:  in Thread Title in  
Simon Barr16/08/2020 18:28:03
26 forum posts
18 photos

Is anyone able to identify this incomplete dividing for me. I picked it up locally cheap with the intention of trying to complete it or attempt to turn it into something useful. It was sold to me as made from a kit and GH Thomas plans in the book workshop techniques, however from pictures I can find on the Internet it looks a bit different to the GHT one.

Dividing is a new thing to me but I gather knowing the ratio of the turns is important. It appears to be 60:1 and the plate on it has 24 holes. Apparently the thread is to suit a Boxford chuck.

I'd love to get it functional if I can by making or buying what is needed but first I need to know who's plans it was made to.

Thanks, Simon

img_20200816_180033 - edited.jpg

img_20200816_180046 - edited.jpg

img_20200816_180053 - edited.jpg

not done it yet16/08/2020 18:35:28
6519 forum posts
20 photos

Maybe start by looking on the Hemingway site?

Simon Barr16/08/2020 19:06:53
26 forum posts
18 photos
Posted by not done it yet on 16/08/2020 18:35:28:

Maybe start by looking on the Hemingway site?

That is one of the places I've already looked. The kit on that site appears to be different to what I have unfortunately hence me asking here to see if it rings a bell with someone.

Martin Kyte16/08/2020 19:43:35
avatar
2637 forum posts
46 photos

It's a George Thomas versatile dividing head but the maker has fabricated the body. Do you have any plates or the rest of the micrometer adjust worm ?

regards Martin

Simon Barr16/08/2020 19:51:51
26 forum posts
18 photos

All I have is in the photos. I was hoping that once I have identified which design it is I may be able to fabricate/buy any other parts I need. I made a gamble buying it but hopefully I can put it to use somehow. It appears to be well made, I've just got back in from the garage and dismantled it as far as I could the inspect it.

If you think it's based on the GHT design then I at least have something to go on in my research. Thank you.

Roderick Jenkins16/08/2020 21:20:25
avatar
2137 forum posts
586 photos

The worm assembly is certainly GHT. I made the Headstock Dividing Attachment which uses the same dividing plates, sector arm and micro adjustment as the Versatile Dividing Head.

ej2.jpg

timmins head.jpg

In a similar way to the original maker of your DH, I adapted a base, in this case the Timmins, to take the GHT stuff.

Your base looks very nicely made, possibly milled out of a solid lump. You will see that I have also made it possible to do direct indexing in the holes as well as via the worm and wheel. GHT's Dividing and Graduating is available second hand **LINK** somewhat cheaper than buying the compendium Workshop Techniques.

Hope this helps,

Rod

Hopper17/08/2020 02:45:25
avatar
5508 forum posts
137 photos

Nice. If you make the fine adjustment worm and graduated thimble to fit on that second small worm gear, you can use it to generate its own indexing plates using GHT's diabolically cunning method.

Have fun drilling all 812 holes. And then chamfering both ends of each hole. 😁

dscn2978.jpg

 

Edited By Hopper on 17/08/2020 02:46:08

Edited By Hopper on 17/08/2020 02:48:24

not done it yet17/08/2020 06:23:14
6519 forum posts
20 photos
Posted by Simon Barr on 16/08/2020 19:06:53:
Posted by not done it yet on 16/08/2020 18:35:28:

Maybe start by looking on the Hemingway site?

That is one of the places I've already looked. The kit on that site appears to be different to what I have unfortunately hence me asking here to see if it rings a bell with someone.

Maybe yours was castings supplied by another company? An earlier one, before minor modification/improvement by Hemingway? Car models retain the same basic design but bodywork and engineering details change with later versions. One must accept what your eyes see, taking into account possible alternative sources.

Some kits are now metric instead of imperial or modified to accommodate both system details. The Hemingway site at the very least should have provided you with all the missing parts and details of where to locate build. It was all there for you if you simply used that as a starting point.

Hopper17/08/2020 07:26:55
avatar
5508 forum posts
137 photos

The Hemingway Kit Versatile Dividing Head appears identical to that in GHT's book "Workshop Techniques". As GHT includes drawings in the book for making your own patterns to get castings done, I think Hemingway still uses his original design.

However, GHT does mention in the book that his was not the first VDH. That was made by his friend, referred to only as "A.B.", following discussions with GHT. He writes that that A.B. "made it up from available materials". GHT then went on to design and make his own version with its own castings, appearing the same as today's Hemingway kit.

Could this one above be the original pre-GHT prototype made by the mysterious "A.B."....?

Either way, all the running gear as described in GHT's book should work for you. It appears to be only the casting that is different. The fine adjustment attachment and the indexing plates should be the same.

Or if you just want to get going and use the dividing head, a set of commercially available indexing plates from any 60:1 ratio dividing head should be able to be adapted to fit. Costs about 40 quid for the three plates with the crank arm and plunger and sector arms.

Albeit, the 24 holes in the side of the main gear will do most jobs if a suitable bracket and plunger are made up so it can  be used as a spin indexer basically. Also, the 60 teeth of the gear with a suitable plunger can be used to get a few more numbers of division done, such as 5, 15, 30, 60 etc.

 

.

 

Edited By Hopper on 17/08/2020 07:47:57

Edited By Hopper on 17/08/2020 07:51:25

Edited By Hopper on 17/08/2020 07:56:34

Clive Foster17/08/2020 08:07:31
2990 forum posts
105 photos

What is the centre height?

Looks to me like a hybridised Geo. H Thomas VDH / Tom Senior design re-worked for home construction by carving from solid and sized to match a Boxford or SouthBend 9" clone.

Basic layout follows the Tom Senior design, which also used a Boxford compatible spindle nose, but the worm drive and carrier arrangement is GHT.

Way back I looked into fitting a GHT drive set up onto a Tom Senior head that had lost its original worm drive and plates. From memory the size and relative dimensions from your pictures look similar to my concept sketches. Objectively the over the top arrangement of the GTH worm drive isn't completely ideal but made necessary by size constraints. With a slightly bigger device the Senior arrangement is preferable.

Nice unit but I'm surprised that the builder used a simple split body and closing screws to clamp the spindle rather than the GHT floating collet system.

Clive

Edited By Clive Foster on 17/08/2020 08:08:29

ega17/08/2020 11:19:38
2399 forum posts
196 photos
Posted by Hopper on 17/08/2020 02:45:25:

Nice. If you make the fine adjustment worm and graduated thimble to fit on that second small worm gear, you can use it to generate its own indexing plates using GHT's diabolically cunning method.

Have fun drilling all 812 holes. And then chamfering both ends of each hole. 😁

...

Surprisingly, GHT did not chamfer his but, IIRC, just cleared them with a hand-held twist drill.

Hopper17/08/2020 11:42:14
avatar
5508 forum posts
137 photos
Posted by ega on 17/08/2020 11:19:38:
Posted by Hopper on 17/08/2020 02:45:25:

Nice. If you make the fine adjustment worm and graduated thimble to fit on that second small worm gear, you can use it to generate its own indexing plates using GHT's diabolically cunning method.

Have fun drilling all 812 holes. And then chamfering both ends of each hole. 😁

...

Surprisingly, GHT did not chamfer his but, IIRC, just cleared them with a hand-held twist drill.

Yeah he was a bit of an old bodger. laughlaughlaughlaugh

Hopper17/08/2020 11:44:48
avatar
5508 forum posts
137 photos
Posted by ega on 17/08/2020 11:19:38:
Posted by Hopper on 17/08/2020 02:45:25:

Nice. If you make the fine adjustment worm and graduated thimble to fit on that second small worm gear, you can use it to generate its own indexing plates using GHT's diabolically cunning method.

Have fun drilling all 812 holes. And then chamfering both ends of each hole. 😁

...

Surprisingly, GHT did not chamfer his but, IIRC, just cleared them with a hand-held twist drill.

Yeah he was a bit of an old bodger. laughlaughlaughlaugh

I rather gathered from comments in his book that the kit at time of the original writing included indexing plates that had been stamped in a press so they came with the requisite holes in them already. Not sure if today's Hemingway kits include holes, or if you have to provide your own.

old mart17/08/2020 13:08:16
3520 forum posts
216 photos

As already mentioned at least twice, the body looks like it is milled from solid rather than a casting which would suggest that it is a one off shop made item. In the days before cnc, it was much more cost affective to buy in batches of castings for finish machining than milling from solid.

When I was in aircraft engineering making parts for Airbus amongst others, we made lightweight brackets which were part of the undercarriage, they carried hydraulic and electrical lines. They were castings, and did not require much machining. However, it turned out to be cheaper to mill them out of solid rather than pay for the castings and £100 each for the mandatory X ray when the solid ones could be NDT tested in house. Only using CNC machinery could the saving be made, plus a lot of swarf, (about 90%, I would estimate).

ega17/08/2020 15:08:10
2399 forum posts
196 photos

Hopper:

I couldn't immediately find your Hemingway reference but GHT does say "The new plate material (En1a) will drill very much better than the punched plates that I used" (p198 of Workshop Techniques).

I wonder if the "old bodger" is still turning in his grave?

Simon Barr17/08/2020 17:29:56
26 forum posts
18 photos

Thanks everyone, it's all becoming clearer for me now. My initial confusion was because it looks very different (Body shape) from the Hemmingway kits causing me to doubt if it was a GHT design or not. Also to clarify the body does appear to be milled from solid and the centre height is approx 3" or 77mm measured in a quick, not very precise way.

As it seems to be universally agreed that it is GHT design in part I feel positive that I can get it to completion in the future. With that in mind I found a copy of the book Roderick mentioned on eBay for £6 so I have ordered it. When that arrives I'll have a set of drawings that I can compare to what I have already and draw up a list of what's needed.

As for dividing plates I will maybe use my mill once I have installed the DRO currently sitting in boxes as it has a PCD function. But I may change my mind once I see GHTs text in the book.

Thanks again everyone for your input, most helpful.

Hopper17/08/2020 22:14:01
avatar
5508 forum posts
137 photos
Posted by Simon Barr on 17/08/2020 17:29:56:

Thanks everyone, it's all becoming clearer for me now. My initial confusion was because it looks very different (Body shape) from the Hemmingway kits causing me to doubt if it was a GHT design or not. Also to clarify the body does appear to be milled from solid and the centre height is approx 3" or 77mm measured in a quick, not very precise way.

As it seems to be universally agreed that it is GHT design in part I feel positive that I can get it to completion in the future. With that in mind I found a copy of the book Roderick mentioned on eBay for £6 so I have ordered it. When that arrives I'll have a set of drawings that I can compare to what I have already and draw up a list of what's needed.

As for dividing plates I will maybe use my mill once I have installed the DRO currently sitting in boxes as it has a PCD function. But I may change my mind once I see GHTs text in the book.

Thanks again everyone for your input, most helpful.

Good stuff. If you can drill the index plates with the DRO you don't really need to make the secondary micro adjustment setup -- other than as an exercise and because it is just way cool to have an accuracy of 1000th of a degree.

Hopper17/08/2020 22:16:45
avatar
5508 forum posts
137 photos
Posted by ega on 17/08/2020 15:08:10:

Hopper:

I couldn't immediately find your Hemingway reference but GHT does say "The new plate material (En1a) will drill very much better than the punched plates that I used" (p198 of Workshop Techniques).

I wonder if the "old bodger" is still turning in his grave?

That's the reference I was thinking of. Does sound though like only the OD was punched out of flat plate and not the myriad holes. That would have been quite the die to do that when you think about it.

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Latest Forum Posts
Support Our Partners
JD Metals
emcomachinetools
Warco
Eccentric July 5 2018
MIDLNDS GARDEN RAIL Jan 2022
cowells
rapid Direct
Eccentric Engineering
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest