HEMINGWAY DIVIDING ATTACHEMENT

[Don1966]

I finally started the Dividing attachment. This is my attempt to construct it. After completion of the attachment I will have the ability to do dividing to1/1000 of a degree on my Myford Super 7 Lathe. I start out the kit with the bearing bar. G.H. thomas suggust that you check the bearing bar for flatness. So I check it with my Starret DTI on the sufrace plate and had .0005 error only in one spot. so not to bad I procedded to mill drill the holes and slot mill the recesses. next was the retaining clip which will hold the swinging latch bar. That was pretty easy just drill one hole and 45 the ends then clamp to the bearing bar and drill a 3/16 hole for holding the swinging latch bar.

First checking the bar for flatness and you can see the .0005 offset.

starting to drill the holes in the bearing bar to 3/16 with a 5/16 recess.

This is the cross bar which will hold the attachment to the lathe by way of knurled screws on each side of the lathe into a 60 degree V which I am drilling. I first squared it in the vise and found the edge dial in the values and drilled.

next I had to make a jig to bind oval on the swinging latch bar. I choose a 1" round bar and drilled a hole in the center on the round edge and secured the flat stock to it. I installed it into the vise and gave it some love taps witha plastic head hammer to final size.

The oval for the swinging latch bar after bending. I then mounted it into the mill vise and drilled the holes through the two connecting U clamps.

Well thats all for today
Don

[Chris J]

I'll be interested to see how this progresses.

I have to say that as a relative newbie who lives in isolation on the edge of the world these kind of threads are a lifeline to me and probably others too.

Thanks Chris

[Jo]

the Versatile Dividing Head which accepts many of the parts on your HDA.

Does it , I was not aware of that maybe I should get mine back out and have a look .

Jo

[Goldstar31]

Jo,
     The division plates, sectors and so on are interchangeable as is the micro adjustment. Again, and i am going a bit off at a tangent, is the Thomas universal pillar tool and drill which will go on to the Myford saddle. With a bit of ger-fiddling, the accessories for the VDH go on the Myford nose and with a bit further mind bending, my Vertex head takes the lot. So much for me nattering in the local 'ink pen' shop with an old buddy  who collects music instruments and airguns-and his family had 'light bulbs' and battleships.

It is keeping a clear head- after a night at the Goat and Compasses that is needed.

Regards

N

[steamer]

Nice setup Don!  Well done!

Dave

[ths]

Hi Don,

I've been looking forward to this one. I haven't done anything about the worm yet, which I think I mentioned last year when you received the kit. Like Norman, I've got the VDH, and am looking forward to your progress on this one. Nice bend on the latch!

Cheers, Hugh.

[ScroungerLee]

Nice, this will be fun to watch.  Did you really mean 1/1000th of a degree? Or of a revolution?

Lee

[mklotz]

I too am skeptical.  A millidegree is only 3.6 arcseconds, an unimaginably small angle.

The deflection of light from distant stars by the sun is only about half that value.

[Don1966]

Wow! seem I got a lot of replies here. First I believe I added one to many zero to the degree division. I will have to find the reference material to justify this. By the way thanks guys for all the replies and looking in.

Hugh the worm gear came all machine but the shaft part. I will not have to turn the actual worm itself just the shaft to dimensions.

Ok back to more progress on the attachment. I managed to complete the swinging latch bar and made a nut for it. Clean the cross bar and the bearing bar.

I hadn't completed the bearing bar yesterday I still need to make the retaining clip. This was just a 1"x1"x1/4 pieced that had to be squared and some 45 degree bevels and each side then drilled. I place the bearing bar into the vise with the clip secured and moved it flush with the corner of the vise and drilled the mid hole between the clamp and the bearing bar, just to make sure it didn't move.


I started out by Silver soldering the U clamp to the bar of the swinging latch bar.

I then cut the loss end off and clean it all up with a little filing to round the edges. I even managed to make the nut for it. BTW I had also thread the bar and bent it.

Just a shot of what I have completed so far.


If you look below I inserted a PDF photo of the Dividing Attachment to see what it will look like.
Well that is it for today maybe tomorrow I will have more to add. Next week I start a job which will last for the whole week so after tomorrow I will have a slight pause.

Don

[Chris J]

Thanks again Don 

[Don1966]

OK, I did some reading and my orginal post of 1/1000 of a degree was right. If you have the G.H. Thomas's "Workshop Techniques Manual" Look it up on page Chapter 19 "The Simple Indexing Attachment". I know I wouldn't argue with his math. I have attach the pages from the manual and highlight in yellow where to read for those who don't have his book.

don

[Goldstar31]

Good Morning Don,
                             I really think that some of the comments here are 'a wind up'. When I got my first edition of GHT's Dividing and Graduating( the original book after GHT published in Model Engineer earlier) I wondered a bit about the comments.
Eventually, it dawned on me that GHT was correct in saying that the dividing heads actually got more and more accurate as each was made from its earlier plate- rather than the reverse.

It was not until I watched a tv programmme on the Gutenberg printing press being made again with its screw thread being cut with a wood chisel that I realised that George's words had accuracy.

I'd made the classic 'one hole' division plate which you will get to.

What does concern me is the just how negative some of the criticism is here.

Again, I wish you real enjoyment from constructing one of construction of yet another of George's designs.

Norman

[Jo]

What does concern me is the just how negative some of the criticism is here.

Norman,

I think that both Lee and Marv were polite in their questioning of the accuracy of the head. On other forums I have noticed they spend most of their time delivering negative criticism of others work and then they wonder why no one will post their builds. Don't worry if I feel anyone is getting out of hand they will be adequately reprimanded.

I was fully aware of the accuracy of my GHT head, but I have never found the need to go to the level of accuracy it can provide.

Jo

[tel]

Yeah Norm, I think that were well within the bounds. At first glance 1/1000° seems pretty fine, bur consider that (by my rusty mental processes) it equate to roughly 1/16" at 100 yards. I got levels that will pick up that much error.

[tel]

No need Norm - open discussion is what it's about eh!