Author Topic: Building a New Lathe  (Read 166088 times)

Offline vtsteam

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Re: Building a New Lathe
« Reply #650 on: July 15, 2018, 08:18:06 AM »
Simon

'Chinese metal' appears regularly in such things as vehicle carburetors and in model engineering, the feed nuts on Myfords are a zinc alloy.

One fault is that it does corrode until after a certain point it will be nothing more than white fluff! Chemically, it is somewhat worse than cheap brass.

However, it is easy to cast and I have rather a nice Unimat clone lathe made from -- lots of it.

Probably 'metal' for typesetting is something similar.

I hope that I haven't stolen the original post-- but Simon did ask

Norman

No problem adding to the conversation Fergus.

I would qualify the statement "it does corrode until after a certain point it will be nothing more than white fluff!" by saying that iron and steel will corrode until after a certain point they will be nothing more than red dust.

You are speaking of unprotected metal exposed to outdoor or saltwater environments, or road salt, which is true of both metals. Bronze and some aluminum, and corten steel alloys are the only answer for corrosion.

With regard to cheapening metal parts by use of die cast zinc alloys, the cheapening is mainly due to the ease of die casting these alloys allowing absolute minimum parts thicknesses and the very high strength of the material -- everything of that sort is hollow and usually 1/16" thick -- car door handles and such. It's a whole different ballgame in a 1/2" or 3/4" thick part, painted, except for wear surfaces and used in a lathe.

As an example, my own unpainted lathe, which has both steel and zamak parts, sat for a couple years in an unheated cinder block shop, with ice on the floor all winter.  When I returned to it this summer, the zinc parts had dulled to a nice evn gray, not white fluff, but a gray patina, looking very much like plain anodized aluminum. Quite servicable, as is.

On the other hand the carefully scraped and oiled steel ways had spots of surface rust which had to be removed. My drill press table was orange with surface rust, as was my iron vise, and just about everything else ferrous.

So, yes in certain applications -- chromed auto hardware, for instance, zinc alloys have been used to cheapen products, and corrosion may be a problem. But that doesn't have to be the way they are used. I think they have great advantages if used with a different approach, and I certainly wouldn't have gone to the trouble of putting them into my own lathe if they weren't ideal (from my perspective) for certain parts. After all I can cast Iron, brass, bronze, aluminum, and obtain and machine steel easily. And have, where I thought appropriate. I used zinc alloys by choice for purpose not cost reductions, and not for ease of machining (ugh!)
I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #651 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:
I love it when a Plan B comes together!
Steve
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Offline awemawson

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Re: Building a New Lathe
« Reply #652 on: July 15, 2018, 09:20:50 AM »
You're like me Steve - you rise to the challenge. If someone says to me that something can't be mended it's like waving a red rag at a bull and I dig my heels in and charge!
Andrew Mawson
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Offline Neubert1975

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Re: Building a New Lathe
« Reply #653 on: July 15, 2018, 09:32:19 AM »
sounds like a person i have been arround since birth  :)
When people tell me that things cant be done, i often answer, in that case i must be a magician.
and if i havent done it, it is like awemawson says, like waving a red rag at a bull  :thumbup:

Offline vtsteam

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Re: Building a New Lathe
« Reply #654 on: July 15, 2018, 09:37:30 AM »
btw, sorry just one more a humorous thought, I have a 20 year old garbage can (dustbin, Br.) that lives by the road, outdoors in all Vermont weather. It is hot dip galvanized steel (zinc coated). It's in fine shape -- no deterioration, despite its rough use, exposure to rain, corrosive contents, and proximity to road salt.

If it had been plain steel of the same thickness, treated this way for twenty years, it would indeed now be a small pile of rust flakes. My 20 year old house roof is also made of galvanized steel sheeting. In fact the very roof that protects my ferrous machine tools from the elements is also zinc coated.

I know some rake is going to point out the galvanic series now, and trot out old saws about anodic protection, but I would ask that he or she then consider all-zinc roofs. No steel couple. Why in the world choose a metal that will turn to white fluff to protect against the elements?

Tell me when my zinc headstock will be powder, so I can switch off the lathe in time, boys!  :lol:
I love it when a Plan B comes together!
Steve
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Offline Neubert1975

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Re: Building a New Lathe
« Reply #655 on: July 15, 2018, 10:14:09 AM »
btw, sorry just one more a humorous thought, I have a 20 year old garbage can (dustbin, Br.) that lives by the road, outdoors in all Vermont weather. It is hot dip galvanized steel (zinc coated). It's in fine shape -- no deterioration, despite its rough use, exposure to rain, corrosive contents, and proximity to road salt.

If it had been plain steel of the same thickness, treated this way for twenty years, it would indeed now be a small pile of rust flakes. My 20 year old house roof is also made of galvanized steel sheeting. In fact the very roof that protects my ferrous machine tools from the elements is also zinc coated.

I know some rake is going to point out the galvanic series now, and trot out old saws about anodic protection, but I would ask that he or she then consider all-zinc roofs. No steel couple. Why in the world choose a metal that will turn to white fluff to protect against the elements?

Tell me when my zinc headstock will be powder, so I can switch off the lathe in time, boys!  :lol:

Lets just say, that i wouldent save materials for that day, i dont think it will come for the first 20+ years  :beer:
/quote]

Offline Fergus OMore

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Re: Building a New Lathe
« Reply #656 on: July 15, 2018, 10:22:27 AM »

Perhaps -a salt and battery? :scratch:

Somewhat whimsically

Norm

Offline vtsteam

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Re: Building a New Lathe
« Reply #657 on: July 15, 2018, 10:39:46 AM »
Okay, off the jokes, here's some simple data re. casting.

Zamak 2 Ultimate tensile strength is 52,000 PSI (apologies to metric folks, but just for relative comparison)
Zamak 12 is 58,000 PSI
SAE1008 steel is 42,000-52,000 PSI
Named aluminum casting alloys ~ 45,000 PSI

For yield strength:

Zamak 2 = 41,000 PSI
Zamak 12 = 46,000 PSI
SAE1008 steel = 20,000-40,000 PSI
Named aluminum casting alloys ~ 22,000 PSI
I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #658 on: July 15, 2018, 11:16:06 AM »
So what are the implications of the above? Well yes, cast parts can be cheapened by a manufacturer, because it is so strong, you can design a part to use very little material, by forcing it into webs and hollow shapes. They feel cheap, too because they are relatively light in weight. And they are brittle because the thin webs have ironically, the tremendous yield strength of the material.

Now suppose you don't want to cheapen a part. But are looking to endow a lathe (for example) with high strength and stiffness. So you build parts with equivalent thickness in ZA-12  to cast iron or steel. In this case the yield strength of the part will be enormous. Greater than any other metal you could cast.

The parts won't be brittle in any practical sense, because the application can never come close to generating yield  forces. The strength of the part will exceed most everything you could build out of except hardened tool steel. The mass will be substantial, because Zamak weighs almost as much as iron. It won't feel or seem cheap or insubstantial. When painted, one casting looks the same as another.Iron is also painted for resistance to rust.  Zamak does have the advantage of bearing slipperiness, so it will be better than steel for slides, and stronger there than cast iron, which is also a good bearing.

In other words, for me, it was the material of choice.
I love it when a Plan B comes together!
Steve
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Offline WeldingRod

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Re: Building a New Lathe
« Reply #659 on: July 15, 2018, 11:20:50 AM »
I think y'all are worrying about zinc pest:
https://en.m.wikipedia.org/wiki/Zinc_pest
Modern lead free alloys don't suffer from this.
Fascinating reading!

Sent from my SAMSUNG-SM-G891A using Tapatalk


Offline vtsteam

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Re: Building a New Lathe
« Reply #660 on: July 15, 2018, 11:57:32 AM »
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).
I love it when a Plan B comes together!
Steve
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Offline S. Heslop

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Re: Building a New Lathe
« Reply #661 on: July 15, 2018, 12:32:55 PM »
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:

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.

Offline vtsteam

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Re: Building a New Lathe
« Reply #662 on: July 15, 2018, 06:20:23 PM »
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.

I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #663 on: July 15, 2018, 09:18:36 PM »
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.



I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #664 on: July 15, 2018, 09:28:42 PM »
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.

I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #665 on: July 15, 2018, 09:34:16 PM »
Since there's no draft, only the wiggling allows the pattern to be removed. But because on a narrow part like this, there is little circumference, there is also reduced drag compared to something more massive.

Here I've finished  withdrawing patterns, and as an experiment I also made a pouring basin and runners (channels). I was thinking this might trap impurities and reduce the chance that I would collapse the part hollows by pouring directly into them. In the past with a single part, I just poured directly -- with good results. But this time I wanted to try something slightly more sophisticated.

I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #666 on: July 15, 2018, 09:36:45 PM »
I'd started the furnace when I started molding. It was ready when I was.

The pour w/ Zamak12. It starts out shiny as mercury. Total molding and melt time: 20 minutes.:

I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #667 on: July 15, 2018, 09:38:24 PM »
And in an other 20 minutes it looks like this. There is a typical hexagonal crystalization barely noticeable. Minor shrinkage (mainly due to the small volume of the parts.)

I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #668 on: July 15, 2018, 10:55:13 PM »
This is the shakeout immediately after the last pic.



I took file to the top and bottom, then took 3 thou off of both on the mill.  The upper piece has been rough filed, the lower skimmed on the mill. The tops will be final milled once attached to the cross slide so they end up flat and even.



Here's the skimmed piece with the wooden pattern that made it. Notice how closely the dimensions match the original pattern. Wiggling the patterns in the mould increased the cavity size by a tiny amount, but shrinkage and filing flat compensated, so the pieces have near identical sections..



Total time from concept, cutting rough stock for 16 patterns, sanding and finishing 4 of them, molding 2 of them, melting metal, casting, cooling and having in hand metal parts was 1 hour and 20 minutes.

I don't know of any pop-tech method that could compete for speed cost or simplicity or conservative use of materials and fuels than ordinary direct pattern making and casting.

I'm not trying to prove that one way is "better" than another, because this is all hobby stuff, and the interest and challenge are the most important products, not the objects we produce. But I do want people to understand the reasons for my personal choices -- many younger people do not actually understand them.

I do it this way because it gives me great joy to move that fast, that directly, and that easily from what I conceive, to what is there, ready to use. That personal choice comes from my own love of traditional skills and efficiencies. There is no intervening program, or computer or robotic tool. It's just me. That's my gas.

I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #669 on: July 15, 2018, 11:08:24 PM »
And the same section we started with in metal:

I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #670 on: July 15, 2018, 11:21:15 PM »
And since it was so easy to do the first two prototypes, and they turned out so well, why not do it again, only this time with four in a "spray"?

I'd started the last batch after 1:00. Plenty of time to do the rest before dinner time. So, hope this isn't too repetitious but


Skull and Crossbones?:


I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #671 on: July 15, 2018, 11:22:04 PM »
Patterns wiggled out:

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Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #672 on: July 15, 2018, 11:22:47 PM »
Metal poured:

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Steve
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Offline vtsteam

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Re: Building a New Lathe
« Reply #673 on: July 15, 2018, 11:23:21 PM »
More T-bars:

I love it when a Plan B comes together!
Steve
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Offline Neubert1975

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Re: Building a New Lathe
« Reply #674 on: July 16, 2018, 09:29:15 AM »
i like the way you made those castings, its one i will remember when i need some parts that would fit that way of doing it  :beer: