Casting about for cast iron casting ideas

[Graziano]

Now say that title again, only quickly :)... I'm thinking of trying some cast iron in the not too distant future and would like any ideas for things to make in iron.

About all I can think of at the moment would be two sets of arbor supports for a certain Eastern European milling machine (yes RC, I haven't forgotten you either :2tsup:) and maybe a 60cm I beam style straight edge as they are supposed to perform better than camelbacks. My local casting guru tells me he has a sack of zirconium flour for coating the moulds to prevent any nasty hard silicon carbide forming on the surface. Apart from that it should be on a par with casting bronze in that iron melts a bit higher in temperature.

[Ueee]

How bout a new compound slide for Blondie?

But seriously, I have cast brass and al before but to cast iron is sort of the holy grail for me. I'd be making a good range of vises, maybe some Kingway tool parts, a grinder rest or two....the list goes on.

Ewan

[ian]

Are you thinking cast iron or cast steel?

Out of interest how will you get the metal to pouring temperature?
and what will you use as the casting medium?

[Graziano]

Ueee, there's a few aluminium alloys a lot stronger than cast iron, don't know how they age though. It'd be nice to make an aluminium vise with steel on all the wear surfaces




Are you thinking cast iron or cast steel?

Out of interest how will you get the metal to pouring temperature?
and what will you use as the casting medium?

I'll be using iron, steel will ignite into a foamy mess in a gas fired furnace with lots of sparks, smoke and a visit from the fire brigade so it's ruled out unless I get a nice secondhand induction furnace with an inert gas cover.

The furnace is a gas fired one and the moulds will be made of resin bonded silica sand.

[RayG]

Hi Graziano,

How about a few shaper vises, I can do smallish pours of cast iron, but nothing near enough for a decent shaper vise.

I'd be thinking of making a cupola...

Regards
Ray

[Graziano]

Hi Graziano,

How about a few shaper vises, I can do smallish pours of cast iron, but nothing near enough for a decent shaper vise.

I'd be thinking of making a cupola...

Regards
Ray

Hi Ray, this is only an A20 size crucible from memory, wouldn't a shaper vise be fairly big and beefy?. I guess you could get a decent size as it would be comprised of at least two castings. Just how different is a shaper vise from a mill vise anyway?.

[RayG]

Hi Graziano,

Shaper vises come in all sizes, 10 or 12" would be a pretty fair size. I'd guess all up weight might be in the 80 - 100 kg range, an A20 crucible, would be 20 pounds or is it 20 kg of bronze, I can never remember.

Anyway, it's not relevant, it would need to be a fair bit bigger for what I was thinking.

You mentioned cast steel throwing sparks and fumes? I've never tried casting steel, but with the cast iron, I mix in layers of charcoal and soda ash with the cast iron, when loading the crucible, to form a layer that stops oxygen from stripping the carbon out of the cast. Would that same approach work with steel?

Regards
Ray

[Graziano]

Hi Graziano,
You mentioned cast steel throwing sparks and fumes? I've never tried casting steel, but with the cast iron, I mix in layers of charcoal and soda ash with the cast iron, when loading the crucible, to form a layer that stops oxygen from stripping the carbon out of the cast. Would that same approach work with steel?

Regards
Ray

The A20 would be 20Kg of bronze, it really needs two people to pour it easily.

I understand steel casting is even more specialised than stainless steel, if molten steel doesn't have some kind of gas blanket it can react with air and actually ignite with oxygen, foaming up and overflowing the crucible. In the old days of crucible steel they used green glass chips to melt and form a covering a bit like a flux layer but I don't know if they were pouring it out of the crucible after making the steel. Charcoal might react with the steel and form cast iron instead of steel.

The guy who's teaching me definitely doesn't want to revisit the experiment after the last time and rates it as worse than the time they had accidentally fed a piece of scrap magnesium from an old Victa mower base into the furnace.

[RayG]

The guy who's teaching me definitely doesn't want to revisit the experiment after the last time and rates it as worse than the time they had accidentally fed a piece of scrap magnesium from an old Victa mower base into the furnace.

Hi Graziano,

I can imagine magnesium would be a bit of excitement, I actually bought some magnesium ribbon with the idea of adding it to a cast iron pour, they do this in foundries when producing SG cast iron, the magnesium acts as a nodularizer, but what they do is have a special capsule of some kind that they submerge into the molten cast iron, luckily common sense came to the rescue before I tried throwing magnesium ribbon into the crucible... :D

You can buy nodularizers from foundry suppliers, but I can't recall any brand names, I haven't yet got around to trying it.

Ask your mate if he knows of some product names or suppliers of nodularizers.

Regards
Ray

[Graziano]

Hi Graziano,

I can imagine magnesium would be a bit of excitement, I actually bought some magnesium ribbon with the idea of adding it to a cast iron pour, they do this in foundries when producing SG cast iron, the magnesium acts as a nodularizer, but what they do is have a special capsule of some kind that they submerge into the molten cast iron, luckily common sense came to the rescue before I tried throwing magnesium ribbon into the crucible... :D

You can buy nodularizers from foundry suppliers, but I can't recall any brand names, I haven't yet got around to trying it.

Ask your mate if he knows of some product names or suppliers of nodularizers.

Regards
Ray

Ray, if you sealed the magnesium in a bit of steel tube, it should make it into the molten iron without igniting, there are some bronze additives that are sealed in copper tubes for that purpose like phosphorous.

I've been looking at Budget Casting Supply in the States as they seem to supply small quantities that I'd need. Getting various additives in pre Internet days was a major hassle, even now the local foundry suppliers want to know how many pallets of a particular additive/inoculant you want to buy off them. I was looking for calcium silicide to add to the cast iron which should be a grain refining agent such as they use for making mehanite iron.

Anyway the plan is to use a good source of machinable cast iron such as diesel engine parts and see how it casts without any additives: when it was originally cast it would have had grain refining agents added and should still retain those original properties. If I was melting old barbecue parts and manhole covers I'd be inclined to start adding calcium silicide to try and get something machinable.

Another item I was thinking of making would be a cast iron surface plate around 40x40 cm in size.

Cheers,
Mark

[RayG]

Hi Graziano,

The straight edge idea, is a good one, Suburban make a beam type straight edge.

Are you thinking of this style..

CAST IRON STRAIGHT EDGES by Suburban Tool, Inc. (http://www.subtool.com/st/se-ci_cast_iron_straight_edges.html)

Do you think you could do 36"?

Regards
Ray

[Graziano]

That's kind of like what I had in mind, maybe with a taller web for increased rigidity and a wider base so that dovetails could be machined into the sides of the base. I was thinking of maybe 60cm maximum as I can then use a local surface grinder to grind the bases flat. 36" would be do-able, just not machinable by me.

[PDW]

Hi Graziano,

The straight edge idea, is a good one, Suburban make a beam type straight edge.

Are you thinking of this style..

CAST IRON STRAIGHT EDGES by Suburban Tool, Inc. (http://www.subtool.com/st/se-ci_cast_iron_straight_edges.html)

Do you think you could do 36"?

Regards
Ray

I made a rough pattern for a 750mm one to get some pricing on a casting. Didn't look too bad so making the proper pattern is almost at the top of the project list, as soon as I finish painting the boat interior. I have to dig out the small table saw anyway so I can cut the tapered timber I need to get a pattern that comes out of the sand cleanly. The big saw doesn't do tapers (rise & fall only) and I hate resetting the big band saw when I've other alternatives.

When I get back at the end of next week I'll revisit this, see if I can get the patterns done. My thinking was to make some with flat edges and some with a bottom wide enough to mill for spotting dovetails.

900mm would be possible but 750mm is the biggest I could mill. Once I get my new surface plate though, in theory 1m should be possible on the table diagonal - I think.

PDW

[Bryan]

My thinking was to make some with flat edges and some with a bottom wide enough to mill for spotting dovetails.


You wouldn't make them double-sided, with one side narrow and one wide?

[Anorak Bob]

Hi Graziano,

The straight edge idea, is a good one, Suburban make a beam type straight edge.

Are you thinking of this style..

CAST IRON STRAIGHT EDGES by Suburban Tool, Inc. (http://www.subtool.com/st/se-ci_cast_iron_straight_edges.html)

Do you think you could do 36"?

Regards
Ray

I just looked at the prices.:o I understand the desire to make your own. Does a parallel straight edge have any great advantage over the more attractive camelback design such as this one by Deming?

◥◣36" DEMING CAMEL BACK 45° DOVETAIL STRAIGHT EDGE◢◤ | eBay (http://www.ebay.com/itm/36-DEMING-CAMEL-BACK-45-DOVETAIL-STRAIGHT-EDGE-/370528447870?pt=LH_DefaultDomain_0&hash=item5645376d7e)

BT who has not been to the scape fest and knows nothing.

[ian]

Another item I was thinking of making would be a cast iron surface plate around 40x40 cm in size.staying in this discussion to learn

Mark
given that you have a 20kg crucible, how would you go about making a 400 x 400 surface plate ?
I'm calculating around 60kg of molten metal for such a plate -- allowing for the pouring lip and riser

[Graziano]

Does a parallel straight edge have any great advantage over the more attractive camelback design such as this one by Deming?

It's my understanding that they are stiffer, but at the expense of weight, so in the larger sizes a camelback straight edge is preferable simply for the weight savings. I'd tried to research if they are more stable thermally but never really found out anything (via the Internet anyway).

[Graziano]

staying in this discussion to learn

Mark
given that you have a 20kg crucible, how would you go about making a 400 x 400 surface plate ?
I'm calculating around 60kg of molten metal for such a plate -- allowing for the pouring lip and riser

At this stage I haven't made any firm plans let alone patterns, the A20 will hold 24Kg of leaded gunmetal bronze flat out so the amount of iron is going to be a bit less, say 20Kg. So whatever I make will be have to be limited to that weight.

Edit: just a quick calculation: using a figure of 7.87 for the density of iron, a block 30mm thick by 300mm square will weigh 21.25Kg.....going to be a small small, thin surface plate :C.

[RayG]

I just looked at the prices.:o I understand the desire to make your own. Does a parallel straight edge have any great advantage over the more attractive camelback design such as this one by Deming?

◥◣36" DEMING CAMEL BACK 45° DOVETAIL STRAIGHT EDGE◢◤ | eBay (http://www.ebay.com/itm/36-DEMING-CAMEL-BACK-45-DOVETAIL-STRAIGHT-EDGE-/370528447870?pt=LH_DefaultDomain_0&hash=item5645376d7e)

BT who has not been to the scape fest and knows nothing.

Hi BT,

I don't think there's a huge difference between the traditional camel back and the beam type as far as stability and accuracy goes, temperature stability is the big one of course.. The thing I like about the beam type is that they would serve as big parallels, aside from being easier to setup on the surface grinder or mill.

But practicality aside, those big camel backs do look good... :D

Hi Mark,
As far as size goes, on reflection, I'd be happy enough with 600mm, I could fit that size into the furnace for stress relieving, and what's more 600mm would fit on the surface grinder as well.. so if you are taking expressions of interest :) I'd want to get two of them, rough castings are fine. I can do the rest.


Regards
Ray

[ian]

At this stage I haven't made any firm plans let alone patterns, the A20 will hold 24Kg of leaded gunmetal bronze flat out so the amount of iron is going to be a bit less, say 20Kg. So whatever I make will be have to be limited to that weight.

Edit: just a quick calculation: using a figure of 7.87 for the density of iron, a block 30mm thick by 300mm square will weigh 21.25Kg.....going to be a small small, thin surface plate :C.when I started following this thread I did a quick google for casting information.
From that search it appears that in practical terms, the object being cast can't use much more than 75-80% of the melt, the rest being stored within the mold to flow into the casting as it solidifies and contracts

I like the idea of casting your own straight edge -- maybe you could also do a line of combination heads to rival those from Starrett :)

[Anorak Bob]

Hi BT,

I don't think there's a huge difference between the traditional camel back and the beam type as far as stability and accuracy goes, temperature stability is the big one of course.. The thing I like about the beam type is that they would serve as big parallels, aside from being easier to setup on the surface grinder or mill.

But practicality aside, those big camel backs do look good... :D

Hi Mark,
As far as size goes, on reflection, I'd be happy enough with 600mm, I could fit that size into the furnace for stress relieving, and what's more 600mm would fit on the surface grinder as well.. so if you are taking expressions of interest :) I'd want to get two of them, rough castings are fine. I can do the rest.


Regards
Ray

Given that I'm the first to bleat about space constraints, the advantages of the parallel version's machinability should have been obvious. Sorry boys.:doh:

[jhovel]

Ray et al (large shaper owners),
If you were to make 600mm long parallel I-beam type straightedges, you could make that from a solid strip of cast iron. Just produce the I profile on the shaper, then mill out some slots from the web for wright reduction and grind the 4 long sides of the final articles.
Would that not give you a better likelyhood of a uniform internal crystalline structure?
Joe

[Michael G]

Bob, it's a trade off -
An I beam has two edges, a camel back one. But a camel back shape is such that it makes more efficient use of material. Typically the shape is something like parabolic so that it will deflect less from the effects of gravity. With the I beam shape the corners will deflect down when it is suspended (held).

Michael

[Graziano]

Hi BT,

I don't think there's a huge difference between the traditional camel back and the beam type as far as stability and accuracy goes, temperature stability is the big one of course.. The thing I like about the beam type is that they would serve as big parallels, aside from being easier to setup on the surface grinder or mill.

But practicality aside, those big camel backs do look good... :D

Hi Mark,
As far as size goes, on reflection, I'd be happy enough with 600mm, I could fit that size into the furnace for stress relieving, and what's more 600mm would fit on the surface grinder as well.. so if you are taking expressions of interest :) I'd want to get two of them, rough castings are fine. I can do the rest.


Regards
Ray


Hi Ray, your interest is noted, it's early days yet when it comes to making a successful iron casting let alone getting to the point of selling raw castings. The type of straight edge I'd like to make would look different to the first one you posted a link to. I'm planning on having enough material on top and bottom to machine top and bottom dovetails, length is going to be limited by the A20 pot volume and will be varied to suit but ideally 60cm. When I stop to think about the last casting session it was taking three 8 kilo ingots plus a fair bit of runners and scrap, so about 28+ Kg (just looked up an A20: it's 30Kg of brass capacity).

This is similar to what I'm planning, if you had the same base on top as this one has on the bottom:

http://www.newmantools.com/busch/Image134.gif

http://i13.photobucket.com/albums/a290/stefi1/DSCN0028.jpg




Bob, it's a trade off -
An I beam has two edges, a camel back one. But a camel back shape is such that it makes more efficient use of material. Typically the shape is something like parabolic so that it will deflect less from the effects of gravity. With the I beam shape the corners will deflect down when it is suspended (held).

Michael

Michael, I'd still like to find some definitive comparison between a camelback and an I beam style apart from weight differences and material used. I think for the smaller sizes an I beam could be handier, at least you could have 2 different dovetail angles machined in.

Ok, just a rough estimate on iron required: If I have a top and base 60mm wide, 30mm thick and 600mm long with a web 8mm thick 100mm wide and 600mm long I get a weight of 20.856 Kg which is more than castable with an A20 pot. Add in some cross bracing ribs and place a few holes in the web and the weight shouldn't be much more....still weighs as much as a bag of cement though.

[.RC.]

I think Phil or Marko said they do not use camel backs as you cannot put a level on them...

[bts]

Now say that title again, only quickly :)... I'm thinking of trying some cast iron in the not too distant future and would like any ideas for things to make in iron.

About all I can think of at the moment would be two sets of arbor supports for a certain Eastern European milling machine (yes RC, I haven't forgotten you either :2tsup:) and maybe a 60cm I beam style straight edge as they are supposed to perform better than camelbacks. My local casting guru tells me he has a sack of zirconium flour for coating the moulds to prevent any nasty hard silicon carbide forming on the surface. Apart from that it should be on a par with casting bronze in that iron melts a bit higher in temperature.

Beat thing for checking your molten cast iron after innoculation and before pouring is a wedge test. From this you can see what sort of sectional chill you will have. If you have to much white iron chill for the sections you are casting you can add some more innoculant.

Make your risers as large as you can. Cast iron is the only metal that actually expands for a time as part of its cooling prosses. When it starts to contract you need some molten metal to be able drawn back in so as to produce a solid casting.

Tony

[Graziano]

Beat thing for checking your molten cast iron after innoculation and before pouring is a wedge test. From this you can see what sort of sectional chill you will have. If you have to much white iron chill for the sections you are casting you can add some more innoculant.

Make your risers as large as you can. Cast iron is the only metal that actually expands for a time as part of its cooling prosses. When it starts to contract you need some molten metal to be able drawn back in so as to produce a solid casting.

Tony

Thanks for the practical advice Tony, Does the innoculant (ferrosilicon?) remain when recycling grey cast iron, or do I need to add it every single time I melt?. I wouldn't want to overdo the innoculants.

If I stress relieve the casting afterwards will it eliminate white iron chill?.

[4-6-4]

Greetings chaps, I near fell over when I saw this post. Having been there and done that I was wondering how you were going to raise the 1600 degrees temp you will need to melt the iron. The pieces you are talking about would I think require a substantial amount of iron. Gas would be too slow and would probably not get to the required temp. Oil firing might but it is messy. A supply of coke for a Cupola would be the go. Or as I have done it Electric induction. This is the easy part. The hard part is the sand. used to put the pattern in. This requires moulding boxes. Top and bottom. The preparation of the sand is of importantce as rough sand gives a rough fins. This it true of a rough pattern. Almost all foundries use chemically bonded sand which sets like concrete. In my foundry I used CO2 sand which was set off by gas. If you go the green sand route then you are confronted by the need to prepare the sand after each use by milling the lumps out of it adding the correct amount of water and Bentonite clay which holds the show together. This with some knowledge of the process would be handy. I would advise talking to a patternmaker for advice on patterns and get the articles made at a foundry. But I would be interested in knowing how you get on. Yours 4-6-4

[Graziano]

Greetings chaps, I near fell over when I saw this post. Having been there and done that I was wondering how you were going to raise the 1600 degrees temp you will need to melt the iron. The pieces you are talking about would I think require a substantial amount of iron. Gas would be too slow and would probably not get to the required temp. Oil firing might but it is messy. A supply of coke for a Cupola would be the go. Or as I have done it Electric induction. This is the easy part. The hard part is the sand. used to put the pattern in. This requires moulding boxes. Top and bottom. The preparation of the sand is of importantce as rough sand gives a rough fins. This it true of a rough pattern. Almost all foundries use chemically bonded sand which sets like concrete. In my foundry I used CO2 sand which was set off by gas. If you go the green sand route then you are confronted by the need to prepare the sand after each use by milling the lumps out of it adding the correct amount of water and Bentonite clay which holds the show together. This with some knowledge of the process would be handy. I would advise talking to a patternmaker for advice on patterns and get the articles made at a foundry. But I would be interested in knowing how you get on. Yours 4-6-4

Thank you for the concern 4-6-4, the temperatures reached by this furnace which has been in use since the early 1950's is more than hot enough to melt iron and has been used in the past a lot to melt iron running only off gas. It does however have to be throttled back a bit from flat out as it readily melts the Foseco refractory furnace lining at that setting. It all comes down to the rate at which you burn the gas, in this case very very fast. The furnace comfortably melts bronze which needs about 1150 degrees C to pour well and cast iron melts at about 1200 degrees C so I'd expect you'd need it a bit hotter than that to pour well. Chemically pure iron on the other hand begins to melt at 1535 degrees C but the carbon content of regular cast iron lowers the melting point to around 1200 deg C.

I'll be using 3 component resin bonded silica sand for the castings which I understand is used for iron castings. At any rate it'll be done at the foundry of a friend of mine who is providing the technical expertise.

[4-6-4]

Good to hear about your facilities. I get a bit worried when I read about blokes who are going to play with molten iron. You are definitely on the right track having good advice.
Yours 4-6-4

[Swarfmaker1]

If anyone has a sketch of a straight edge I could probably get some made here in Sydney.I could machine a 36" on the Bridgeport and perhaps get it ground, I know MTA have the facillities to grind them. Thoughts?

[.RC.]

Well a handy foundry item seems to be popular....

I had no idea what these sorts of things were worth.. But they seem to be worth a bit, as well the bidder location are not exactly what you would call prime foundry locations

Metal Analyser, Spectro Model Spectromaxx Type LMF04, S/No. 4R0109 with The Auction (0641-5002737) | GraysOnline Australia (http://www.graysonline.com/lot/0641-5002737/manufacturing/metal-analyser-spectro-model-spectromaxx-type-lmf04-s-no-4r0109-with-the)

[Graziano]

If anyone has a sketch of a straight edge I could probably get some made here in Sydney.I could machine a 36" on the Bridgeport and perhaps get it ground, I know MTA have the facillities to grind them. Thoughts?


Here's a photo of something similar to what I'm planning:
You'll most likely have to make your patterns yourself as that is the most expensive part of the casting process to have made for you.

http://www.woodworkforums.com/attachment.php?attachmentid=203043&stc=1&d=1332916136

RC, I can't say for sure but I understand such things have come down a fair bit in price as modern electronics has made small compact units practical such as those metal analysers the American scrap dealers all seem to use.

[Anorak Bob]

Quite a neat looking bit of gear Mark. No more than it needs to be.

Carpets a nice touch.

[Graziano]

Quite a neat looking bit of gear Mark. No more than it needs to be.

Carpets a nice touch.


Sorry Bob, that's some guy's shed in the States. I did however score a load of non slip red rubber floor tiles 1200 square in size for my floor.

[ian]

Here's a photo of something similar to what I'm planning:
You'll most likely have to make your patterns yourself as that is the most expensive part of the casting process to have made for you.

http://www.woodworkforums.com/attachment.php?attachmentid=203043&stc=1&d=1332916136
does anyone know the shrinkage factor for the metal you're planning to use?

[Graziano]

does anyone know the shrinkage factor for the metal you're planning to use?

Nope....but I know people who do. I was just going to borrow an iron shrinkage ruler for the pattern and put fat runners on it and see how it goes. If it fails, then modify the pattern to suit and try again.

[ian]

Good luck with the shrinkage ruler.
I think many were tossed into long term storage when pocket calculators arrived.
One standard ruler, a table of shrinkage factors and a calculator, and a patternmaker was right to go.

[Michael G]

Searching for 'casting metal shrinkage" gave up this (among others)
Sand Casting: Allowance (http://www.efunda.com/processes/metal_processing/sand_casting_table.cfm)
Usually a reputable source.
Really for what you are doing though it should not matter as any straight edge you make will be complete as it is. I'd be more worried about shrinkage if you were trying to make a part that had to fit/ match something else already made.

Michael

[Graziano]

Searching for 'casting metal shrinkage" gave up this (among others)
Sand Casting: Allowance (http://www.efunda.com/processes/metal_processing/sand_casting_table.cfm)
Usually a reputable source.
Really for what you are doing though it should not matter as any straight edge you make will be complete as it is. I'd be more worried about shrinkage if you were trying to make a part that had to fit/ match something else already made.

Michael

I agree, it's about 0.8-1% for thermal shrinkage. I was more worried about solidification shrinkage which is another thing entirely from the thermal shrinkage. Bronze and aluminium (4.9 and 6.6.%) need a runner that solidifies last to keep feeding the casting as it shrinks and solidifies. Iron can shrink and even expand depending on the type of iron: +5.5 to -4.5%.

Either way a generous runner/feeder that's not completely filled up should do the trick for the first go-around.

[ian]

Searching for 'casting metal shrinkage" gave up this (among others)
Sand Casting: Allowance (http://www.efunda.com/processes/metal_processing/sand_casting_table.cfm)
Usually a reputable source.
Really for what you are doing though it should not matter as any straight edge you make will be complete as it is. I'd be more worried about shrinkage if you were trying to make a part that had to fit/ match something else already made.

MichaelMichael, where I'd be worried is making the web section of the mold too thin for the molten metal to flow into them without risking cavities and the like.

I suspect that the web section on some straight edges is around the thinest possible without experiencing casting failures.
Which suggests that making a sand mold from an existing straight edge could be problematic

[Ueee]

Hi,
Just thought i'd thow another idea in to the mix for one offs or even the straight edge's. I have been doing a bit of research into lost foam and have read it works with iron as well as ally and copper alloys. Using foam means any number of angles, lightening holes etc can be cast in with no fear of mold damage when removing the pattern. And really, how hard would it be to bust out a series of straight items in foam?

Ewan

[Michael G]

Sometimes I look at the product of Victorian Foundrymen and am amazed at the thinness of the sections they have achieved and the length of the runs they could get metal to flow. This all without digital thermometers and thermostatically controlled furnaces.
While geometry of sections is something to consider, I think that there is a lot in the casting process that is art rather than formal smarts - that is, there is a balance between the mechanism of making a cavity and pouring metal into it and 'knowing' the right moment to pour, what temperature the metal should be at, how much in the way of additives are needed in the melt and even preparing the mould prior to pouring.
In a way it's sad that we (as a society) are not prepared to reward excellence in trades as much as we seem to reward say marketing skills or those of a financial trader. I know which occupation I regard as more useful...

Back to the issue at hand -
Lost foam works by the metal melting/ burning the foam when it is poured, so there is no reason that it shouldn't work for almost any casting process. The smell is something awful but like the foam that's a one off too. The foam model has to be a perfect shape though as anywhere there is not foam there will be sand and so metal won't get there. This means you have to have all the chamfers, fillets and blends right on the model for example

I once took a 28" camel back I have to a foundry and asked if they could use it as a pattern to make a copy. It had 1/4" webs and all sorts on it. The answer was yes, but it would cost, mainly because of the difficulty of using it as a pattern - no draft on the working edge, no where to hang onto it to pull it out, dags on the original casting that had not been fettled of when new and the list went on.

Michael

[Graziano]

The inlet manifold on my car looks like it's cast with styrofoam as the resulting manifold has that foam texture, it actually looks like it's styrofoam painted grey. I can see for production work of complicated shapes it would work well.

For a straight edge a normal wood pattern for the straight edge would do the job, there's nothing complicated about the shape of it that would require lost styrofoam. I suppose if I wanted to add an undercut areas to the top and bottom of the straight edge I could insert a strip of foam (to the pattern before moulding the sand).

The resin bonded sand is fairly strong mechanically, it allows patterns with fairly thin sections to be moulded easily without bits breaking off. After casting the resin bonding breaks down with the heat after the metal has solidified which makes cleaning the casting a lot easier than digging solid chunks of sand out.

You can see the resin has let go round the edges of the bronze and gone white and crumbly.
http://www.woodworkforums.com/attachment.php?attachmentid=203290&stc=1&d=1333063132


In this photo, the aluminium hasn't heated the sand enough for it to crumble and it has to be dug out mechanically.
http://www.woodworkforums.com/attachment.php?attachmentid=203291&stc=1&d=1333063132

[4-6-4]

Greetings Chaps The shrinkage for ordinary cast iron is 100 thou per foot. Allow for this plus a healthy amount for machining and you are OK. Instead of Cast Iron I w0ould think about SG Iron This is substantialy stronger than cast iron and machines more like steel. If you are using a foundry let them cut the ingates and runner bars. I read some where on this forum That you should cut ingates as big as possible. This is not right A large ingate takes longer to solidify and could suck metal from the main Casting. The comment about concern that the thickness web on the straight might not run is also inaccurate, Iron runs like water and if it is poured at the correct temperature it will fill the cavity. The only thing I would suggest is a series of risers from the bottom part of the mould to allow the iron to flow through. A split pattern would be advisable on this case. If the mould is vented properly then it should pour and run correctly. I made Parallel Strips 4 inches high and 2 inches wide without any problems. Happy days Yours 4-6-4

[.RC.]

pattern making is where a 3d printer would shine.

[Michael G]

Having just seen Bob's http://www.woodworkforums.com/f65/third-hand-drill-press-150485/#post1466940, I wouldn't mind having one myself (as I suspect would a few others). How about doing a run of the cast part that attaches to the pillar?
It's just a small casting but you could probably make a few dollars out of a batch of them.

Michael

[Graziano]

pattern making is where a 3d printer would shine.

Definitely would be handy to have, once you start making complex curves that have to be accurately made, life is made a lot easier with CNC patternmaking such as the 3D printer or a CNC router. I was checking out the Rapid Replicator project for such a machine, a bit of scaling up and you'd be in business.

http://reprap.org/wiki/RepRap

Hi Michael, it's a neat little device but I suspect it's more for small production runs as it looks like it takes a bit of adjustment up and down the post as well as the table height as the cam locking would need to be changed every time you drilled a different item or changed a drill bit. I don't know that I could cast stuff for an acceptable price for everyone compared with buying the real item. An example would be casting bronze, I think the price for raw material alone is around $20 a kilo. I understand one foundry is charging $28 per kilo for cast iron castings to give an idea of costs.

Edit: Bronze ingot is about $12 a kilo of you buy more than a few hundred kilos.

[Anorak Bob]

I think it would be easy enough to fabricate a version of the hold down. I will post more photos.

BT

[Graziano]

I have used a nice but more complicated holder which has a small pneumatic cylinder operating a lever with a forked end. The whole thing clamps to the drill press table and has about a 20mm clamping range with adjustable pressure via an air regulator. A foot pedal valve toggles it off and on, if you have a hundred items to drill and ream it's really fast. as it attaches to the table there are no downward bending forces to snap the table casting where it attaches to the column.

Though they are hard to find, there are guys down South who make a very good living (or used to, now manufacturing is almost dead) by contracting to drill 5 million holes in a bracket for a hardware manufacturer. They'd set up a gang of drill presses, each with a pneumatic clamp and jig to accurately hold the thingo in position for drilling.