Thread: Casting about for cast iron casting ideas

Originally Posted by Anorak Bob

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).

Originally Posted by ian

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 .

Originally Posted by Anorak Bob

I just looked at the prices. 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

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...

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

Originally Posted by Graziano

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 .

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

Originally Posted by RayG

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...

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.

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

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

Originally Posted by RayG

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...

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:

Originally Posted by 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

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.

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

Originally Posted by 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 ) 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

Originally Posted by bts

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?.

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

Originally Posted by 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

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.

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