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A square rotary table

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vtsteam:
I don't have any rotary table, and I've got a piston to hollow out and a conrod to make and a, well  million other things it seems like I could do if I had one. I mean there's other ways to mill part way around a shape, but you know how it is..... I just want a rotary table!  :Mad:  Gee everybody else has one......

But you know, too expensive, and building a  good one is a major project I'd love to focus on, but that would completely stop progress on the engine I want a rotary table for in the first place. So, what to do........

Well there's this:

http://www.youtube.com/watch?v=qIvcTz7NWII

And that's quite similar to one shown In Dave Gingery's Shop Notebook that I've looked at for years (though his is smaller and round, and more of a fixed angular positioning type). I think it will do what I need to do on the engine, and I can build it pretty quickly from scrap I already have.

I can't afford the big beautiful virgin slabs of 2024 aluminum the poster puts his together with. But I have plenty of aluminum melting scrap, and I can come up with a piece of 4" x 8" x 1/2" hot rolled steel for the base plate, and a piece of 2" square tube for the clamping piece bolted underneath.

So to start this evening I just cut a piece of wood 6-1/4" square and a little over an inch thick as a pattern, and without finishing or drafting it, molded it up in greensand with a simple 1-1/2" pop gate for a sprue. This is casting at its crudest.

An old broken Hobart industrial food mixer paddle was further "piecefied" with a sledge hammer, and chunked into a crucible for melting stock, and placed in the iron furnace. I was again running a small propane burner instead of the usual iron melting oil burner, to keep the melt rate modest.

I added more aluminum as the melt progressed, and had a brimful pot of about 5 pounds of the silver stuff in 20 minutes. The pour was normal, and here is the result. A bit rough and ready, but it should mill down nicely to about a 6" square, and around an inch thick, which is what I'm guessing the video poster was working with

Kim:
Looks like a great start for a fun sub-projet  :ThumbsUp: :popcorn:

You can turn any project into a foundry project, can't you Steve?  :Lol:

Kim

Alyn Foundry:
Hi Steve, Kim.

Most of my projects have started in the “ backyard “ foundry.  ;)

For simple shapes, like your slab of Aluminium for instance, you can reduce much time by using metal dies. This method was used to make most of the Aluminium core boxes that I have. Steel “ C” section forms 3 sides with a plate clamped to close. Stand the mould vertical and pour in the metal to the top. The only real preparation prior to pouring is to heat up the die with your torch to ensure no condensation forms from the cold Steel. Other shapes are also possible made from scrap bits of bright flat Steel stock.

I kept the broken window Glass from our old wood burner, this makes a really flat seal for you to stand the mould on.

This technique can, and has, been modified to make more complex shapes like bearings or the governor yoke for my IF Allman replica.

 :cheers:  Graham

vtsteam:
Kim, thanks kindly! I started out in the machining hobby by casting first, and making a lathe second. That's because in 2001 I found the Dave Gingery foundry and lathe books, and followed them all the way through, step by step. It's funny, I didn't even know what the parts of a lathe were as I was building one. I just trusted that if I finished, I would understand what they were, how they went together, and how they were used.

That was absolutely the truth, and I have loved casting and machining ever since. It was very empowering to go from complete ignorance to understanding these basic aspects metal working. Before that metal seemed such impossible stuff to imagine shaping into things. After that it became understandable and accessible to me.

So, coming up by that route, it's how I think of things I want to make. It cost very little to build a lathe form scratch -- and I would never have afforded to purchase one and the array of tooling I'd have needed to do useful things. Because I was starting a family and working to save money for land and later for building a house, there was no money for a hobby like machining. But because the Gingery books had you casting with plain simple greensand, and charcoal briquets, and through the kindness of a local engine rebuild shop, fifty pounds of used aluminum pistons, I was able to build a lathe.....and many other things after.

The house is built, my daughter is in high school, but money is still mainly aimed at essential purposes. And of course I truly love making things from scratch -- metal things in particular, so casting for me is closely allied to machining and metal work. Through gradual improvement and upgrade, I can now cast iron, have built a second lathe, and much tooling. Building engines was always the ultimate goal. So, now I'm here.

Haha, well not quite -- now I'm building a rudimentary rotary table! It never ends.....

The Gingery lathe and patterns ca. 2002:



Own design milling attachment for the Gingery:



Milling a compressor scroll with the vertical attachment:

vtsteam:
Graham, thanks kindly!  :cheers: I have not tried casting in metal dies yet. I'm very interested in it for sure. But it would mainly be useful for something you think you're going to make a lot of, and it seems practically everything I make is something new. Very few repeats except for say ball handles, and a die for those would require a cnc or at least a big ball mill (and the mill power to drive it).

I can see that it would be useful for making base aluminum stock, though thick plate is actually not a common need for me.  It's different for subtractive machining projects if you don't cast because you use squared stock to eventually mill down to your desired shape.

But if you cast, the tendency is to cast the complex shape in the first place instead of squared stock. Of course Graham you know all this -- I'm not saying anything new!

Honestly Graham I would very much like to try die casting anyway, so I will try to think of a need next time I do. And I greatly appreciate the suggestion, and any tips. :cheers:

(ps. I have done the inverse and cast steel cores inside aluminum parts to get a finished bore. Even threaded rod to get a finished thread (a short one in a split nut) by smoking (sooting) the steel as a release, and then removing . That's a definite Gingery lathe building method.)

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