@pdentrem: After studying the Martin models, I can see four main differences that stand apart from the Prestech set of castings. Without having the benefit of machining the Martin castings or having run that machine, I think it is safe to say that the following four differences would be considered improvements over the Prestech castings:

  1. The base casting has what appears to be a chip/cutting pan cast into the base. After thinking about this, I'll probably fab up a chip tray for the entire benchtop machine to sit in while in use.
  2. The hob spindle casting appears to be more robust on the Martin model set. Once I have the drawings finished, you will see what I mean about the Prestech. With that said, I don't see this being a show stopper for my project at all. Maybe a future wishlist item if things seem flimsy.
  3. The cardan shaft support bracket, appears to be more rigid given the large gusset in the casting. My support is essentially an "L" with no gusset cast into the part. A gusset could be added though, and was one of the first thoughts to cross my mind when inspecting this Prestech component without the benefit of seeing the Martin model photos.
  4. There appears to be angular setting adjustments in the compound base and in the compound slide for both helical, spiral and possibly bevel gear cutting. This is evidenced by the arc shaped slots in the photos.
These photos were helpful @pdentrem, thanks! It gave me some things to consider as I further study the Robinson modifications for helical, spiral and bevel gear cutting.
 
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There is a YouTube showing the Martin under power. The link is in the Martin site.
Pierre
 
I've been busy creating prints of the castings and subsequent machining prints. See this thread for a sideline discussion regarding casting drawing standards and some reference materials.

As I created the prints, I naturally found myself thinking ahead on the plan to machine these. One of the features of this project is a vertical, cross and longitudinal slides in order to position work pieces in relation to the hob and to auto feed the work piece via the cross slide feed. The slides are of dovetail construction. One of Harold Hall's comments in his three part article is that he standardized the dovetails - I found this to be untrue.

For starters, one of the dovetail pairs interfered with each other by 1/16", so I was scratching my head on that one...this according to the drawings in the article. On another dovetail detail, two dimensions were reversed, defying the laws of physics.

I sketched out all of them in Draftsight, compared the fits and discovered that what Mr. Hall was going for was a 1/8" gib fit between the internal and external dovetail constructions. Armed with a clue, I picked the one pair of dovetails that would work for all three slides.

Drawing attached...
 

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Next set of prints: Item 10 - Longitudinal Slide. Basically working from the bottom of the three axis assembly and up. There are two prints: a casting drawing and a machined drawing. Drawing naming conventions for this project:

X-GH-IXX

First 'X' in the file name is 'C' or 'M' - Casting or Machined,
GH is for the project "Gear Hobber" - doesn't really matter here on the thread but it matters in my project files,
'I' is "Item" as in the itemized parts list. This is helping me key each of my prints to the articles and the drawings from the past, this is helpful again in my personal files, not really relevant to the thread,
'XX' is the Item No. noted in the original Harold Hall articles and CES and Prestech prints - which appear to be copies of each other.

I've included a casting print for those that may want to work backwards and create their own castings...I know its a long shot but I don't see any preservation of the casting dimensions happening anytime soon so I figured I'm the guy to do it.

Machined prints are essentially copies from the articles (if they exist in the article) or my interpretation of the article content and my own design - or a combination of all three.
 

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Bryan,
Interesting project, i've thought about getting the Martin castings. Although i dont why since i have a Mikron 132 gear hobber already. I guess i just want make my own. I do have a small foundry and would like to make my own castings
 
I've got the Martin castings for thier hobber. Interested to see your build.
 
Yikes. Talk about dragging my feet. The past two years have put this project on the back burner. My shop is nearly complete and I'm currently moving my lathe, mill and other various tools into the shop. I haven't cut any chips as a result. However, some time ago I learned about Autodesk Fusion 360 and took the opportunity to learn this software on this project.

294687

I haven't modeled handles or fasteners, so it looks a little bare. More to come this summer.
 
You can download fastener models from McMaster Carr. The only problem is they have modeled threads, which can really bog things down. I haven't gotten this far on the castings yet, so you're way ahead of me.
 
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