Building a New Lathe

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vtsteam:
Good point WR.

I don't melt anything with lead in it (for health and safety reasons), use a separate graphite-clay crucible for Zamak melting only, and use stamped pure known zinc and Zamak-2 ingots, from the same supplier.

The cast parts have shown no deterioration in extreme humidity changes in an unheated shop over 2 years. So-all-in-all I think my lathe is safe from the lead contamination problem (zinc pest).

S. Heslop:

--- Quote from: vtsteam on July 15, 2018, 08:51:25 AM ---Of course, I do enjoy running against conventional wisdom. So far: welded steel lathe beds will warp, firebrick can't be used for melting iron, plaster of Paris won't make a suitable foundry furnace lining, and zinc alloys in a lathe will turn to powder.

Outside of this forum I've been told hundreds of times I can't do things I've managed to achieve, so I guess it's just a normal situation for me. I don't mind, just hope people widen their knowledge base. My firm belief is generalizations are true, except when it comes to specific cases. And even that belief has exceptions! :lol:

--- End quote ---

I think it's important to run against conventional wisdom at least a little bit, especially to make up for differing tooling. I can't see myself ever melting cast iron but I can manage aluminium and presumedly zamak too. The thought of which is rekindling a few project ideas i've had.

I think going against conventional wisdom it's also important for the sake of a community. On the internet especially I feel everything ranges from either a Community - or a Cult of Personality. And where a community innovates and shares ideas, a cult of personality copies ideas and waits for the great masters to bestow more wisdom upon them. Which you can really see in the hacker maker world, not to disparage them too much because there are cool people involved, but the vast majority have a hard time imagining anything outside of the capability of a 3d printer or laser cutter since they're surrounded by media personalities with sponsors and partnerships trying to sell them more.

vtsteam:
Well, I used to feel that way re. pop-tech more than I do now. I don't mind, as long as somebody doesn't tell me that's the only way to do things. In fact I owe apologies for negative sentiments I expressed a few years ago re. 3D printers. Not that I want one, but why shouldn't other people be happy? I just figure, now, that people should do what they're interested in. Including cultivating personal fame if that''s what they want. Me, I like metal, and traditional basic things, and old ideas losing currency now. That's fun for me. I don't like plastic, so I'll probably never make stuff out of it unless there is no viable alternative for something I really want to do.

End of structural politics...... anybody want to get back to making this lathe? And messing with zinc? Okay, then.

Today, I took this organic substance called scrap wood and sawed it into a desirable, to me, shape. This is one of the earliest materials used by man, and it is possible to make it conform to your mental ideas of shape fairly easily with shaped tools and zero programming. It took at most 10 minutes to rip out enough stock for 16 of these patterns, though I didn't need that many -- I just wanted to have enough in case of goof-ups.

It had to have clearance around a Tee nut so it could slide, but enough overhang to hold without breaking, plus clearance to the top surface plus machining allowance. Ordinarily in pattern casting you'd also need draft and shrink allowances, but not in the way I intended to cast this today.

vtsteam:
Raw stock again showing clearances and overlap:

After that I put my sanding sealer on, and waited 15 minutes to dry. Sanded and a second coat, sanded that and was ready to cast. I didn't go for a colored lacquer finish this time -- basically impatient. The castings would have come out cleaner, but I figured they'd be pretty good anyway without.

This is an example of the simplest kind of casting -- open top -- and it's ideal for long narrow uniform pieces, shaped like extrusions. We'll essentially "extrude" out the pattern, and replace it with metal. Maybe we should call this "lost wood" casting! :loco:

Also because you don't need a conventional cope and drag and sprue, the space requirements are minimal. I have cast this way before in a tomato can. I needed a little more height this time so I used a kitchen canister.

vtsteam:
I ram this type of casting mould much harder than I would a conventional flask casting. I'm trying to keep detail crisp, and strengthen the greensand by compacting it hard . I'm not worried about permeability of the sand because the top is open.

I've pulled one of my "extrusion" shapes out of the sand. Too short to rap, I just grabbed it by fingertips, and wiggled gently as I pulled the pattern.

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