Mini Iron and Bronze Furnace

[PatJParticipant @patj87806]

So in summary, it is entirely possible to make very high quality gray iron castings in a backyard setting.

The trick is to use high quality consistent scrap gray iron, such as electrical motor end bells, and follow the methods and materials that are used in commercial foundries.

There is no excuse for any defects in any gray iron casting in a backyard setting, if you use high quality materials.

One should never have to put up with hard spots, inclusions, gas holes, overall poor machinability, etc. in gray iron castings. These defects are totally avoidable in all situations.

And you should never have to temper a gray iron casting in order to remove hard spots or make it machinable.

If you have to temper your gray iron castings, you are doing something wrong.

Some temper gray iron to age it, and I do understand that aging iron may be desirable in engine work.

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[PatJParticipant @patj87806]

Gray Iron vs Ductile Iron:

Gray iron is relatively easy to melt and cast successfully, if you pay close attention to details.

I have researched methods for making ductile iron, and I know how to do it (very carefully with special equipment).

I believe I could easily make ductile iron if someone would sell me the nickel-mag additive (Nickel-Mag4).

I have searched the entire US, and nobody will sell a small quantity of that material.

Nickel-mag has to be the correct mix of materials, else you will get a violent explosion, or start a fire that will burn through a crucible and down into the ground. You actually make ductile iron in a lined ladle, not in a crucible.

If anyone has any spare Nickel-Mag4 laying around, please sent it to me.

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[noel shelleyParticipant @noelshelley55608]

Hi Pat, a very comprehensive expose on foundrywork ! I built my furnace in 1995 and the burner tube still has the paint on it.. Most of my work has been in copper alloys – brasses and bronzes with some aluminium alloys. Look at Dubious Engineering – melting brass in a spin drier. This was filmed at the Midland Expo. Keep spreading the word, I have done my best ! Best wishes Noel.

[PatJParticipant @patj87806]

Thanks Noel,

There is a lot of variety in casting methods out there, and many have their reasons for doing it, such as "its fun on a hobby level", etc.

Definitely there is no one way to do things in the foundry world.

I had a few folks offer advice to me early on, but it was impossible to get a concensus about any method or material, and so I was confused for many years, and almost gave up on backyard iron casting completely.

I know of another individual out west who was mentored by a local iron foundry, and he picked it up in a few weeks.

I pass along this information not with the intent of being a "know-it-all", but rather just sharing what I have learned over 8 years.

If I can save just one person some of the grief and failures I had, it will all be worth it.

Hats off to anyone who tries foundry work.

It is my all-time favorite hobby, and I absolutely love it.

It did take a long time to get to the "love-it" phase though.

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Edited By PatJ on 01/07/2022 19:05:58

[BazyleParticipant @bazyle]

Pat, great to have such advice. In the burner fuel optimisation do you do it with or without the crucible? Can you use a variety of sizes in a furnace or should they be matched, If the latter what is the best crucible to wall gap?

[noel shelleyParticipant @noelshelley55608]

Hi Bazyle A gap of about 3/4" or more will be fine, I tend to use A4,A5 and I can just get an A6 in. As Pat has said if it works go with it !

Pat, in my quest to spread the word I have given talks to over 40 clubs and societies all over the UK and as all my gear is portable most have had me do a working demo as well. In brass. On one occasion a distinguished looking gentleman and his wife were in the crowd, and kept nodding as I was making various point, At one point someone asked a question and the lady seemed to Know the answer, so I said Madam would you like to answer this one ? She did very ably. When the talk was over I made a B line for the couple to find out more ! They were both leading lights at Taylors Bell foundry, Loughborough. I have also had the pleasure of working in a small commercial foundry when I get bored on holiday. Skilled labour is not easy to find so if I turn up they can put me straight to work.One trick I learnt was the use of pre coat resin sand and heated metal core boxes for cylinders and cast in steam ways. If you look in my album you should find some detailed work I've done, the gear wheel was done for pure mischief ! Noel.

[PatJParticipant @patj87806]

Bazyle-

I adjust the burner with the crucible in the furnace, since it provides a significant radiant heated area, which helps with fuel combustion.

I use a Morgan Salamander-Super for all my work, but the Super is ferrous-metal-rated, and rated for 2,900F use, and most other cruibles are not rated for that. The Salamander-Super is a clay graphite material.

I use a variety of crucible sizes in both my mini-furnace and my larger furnace.

The mini wil take an A5 (with a pretty tight fit), all the way down to a 0.5.

In my larger furnace, I often use an A10, but it will accept an A30.

I have been told that it is crucial to have more clearance around a crucible for melting iron, but my buddy built a furnace last year, and he has very little clearance around his A10 (perhaps less than an inch), and he easily melts iron. I have come to suspect that the clearance is more about getting the lifting tongs in place without scratching up the furnace interior.

I think the fact that an A-shaped crucible is much smaller at the bottom also automatically gives a lot more space around the crucible for combustion that one may suspect.

For my small furnace, I follow what Noel says, which is about 3/4" clearance minimum around the top of the crucible.

It is always a joy to talk with anyone who has made any castings, professionally or as a hobby, because one can compare notes and methods, and often discover better ways of doing things.

I know of one individual who worked in a steel mill. What a job that would be, and not doubt HOT !

Noel- I heard that Stuart used some form of resin-coated sand that was cured in a hot mold.

Great process for sure. I will check out your album.

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[Simon CollierParticipant @simoncollier74340]

Pat, thanks for taking the time and effort to record your experience here. Very interesting reading. I wonder if you saw the multi part article on home foundry work in Model Engineer a few years back. I can’t remember by whom. Perhaps it was Noel.

[Simon CollierParticipant @simoncollier74340]

No it was Luke, in 2020.

[PatJParticipant @patj87806]

Hey Simon-

I have never subscribed to ME, but having seen a few photos of engines from the magazine, I think I have missed a lot of great builds by not being aware of this magazine years ago.

I recall seeing one article about a small engine cast in aluminum in a local magazine, and it was many years ago, and I recall being very interested in the process, but totally ignorant of exactly how it was done.

I have some old foundry books, and the US Naval Foundry Manual, but I have never found a very comprehensive overall guide to modern backyard foundry work and furnaces/burners.

I discovered the resin-bound sand being used by art-iron groups here in the states, and they use cupolas to melt their iron.

I bought a book about how to make a cupola, with the intent of building one, but I could never find a source for coke. Typically the how-to backyard casting books I have seen are not really up to date, and they often don't use the most modern materials and equipment available.

The siphon nozzle oil burner seems to be a somewhat recent development in the backyard casting world.

I have seen a few use salvaged oil-fired heating packaged units used with a furnace, but those combo units are rather large and bulky, since the blower, gear pump, and nozzle are all built into one unit.

The pressure nozzle is very similar to the siphon nozzle, and a pressure nozzle works like a perfume sprayer, and uses hydraulic pressure (about 100 psi) to atomized the air. A small gear pump is used for fuel pressure.

I am currently building a pressure nozzle burner, and will retire my siphon nozzle burners, since the pressure nozzle burner does not require an air compressor, and the gear pump uses a very small fractional horsepower motor.

The resin-bound sand really changes the dynamic of foundry work, and the accuracy of the cast parts is excellent. Patterns are pulled straight out of resin-bound sand using a small automotive slide hammer. Resin bound sand sets into a hardened block of material, and since you do not rap the pattern, there is very little distortion or out of roundness in the molds. Castings made using resin-bound sand are almost the same dimensions as the machined parts, and machining the castings requires just light cleanup cuts on the machined surfaces.

I have never found any information about how to use resin-bound sand, and had to learn it from the art-iron folks. Here is one video I found about someone that made slingshots, that illustrates how resin-bound sand is commonly used to make molds.

[noel shelleyParticipant @noelshelley55608]

NO ! It wasn't me Sir ! who wrote the ME article. There have over the years been numerous articles by many authors. The reprint of The US Navy foundry Manual is a very useful book. As for an upto date book, I took up the issue with Chris Deith, who recently passed away, of TEE publishing. It would have been the different ways 3 men had set up and run their own small foundries almost 3 books in one ! His advice was that It would be a vast amount of work and may well not have sold in quantities enough to cover even the costs, due to You tube, HSE and a changing world ! Some of what I see on the Tube Frightens me ! ! 30 years ago there were many books available, I'm not sure how many are still to be had ? For those who have an interest PM me and I will try to compile a list of what WAS available. The books By Steve Chastain are good. TEE and Camden Miniature Steam Services are 2 places to look for books.. The cost of Gas is making me think of using the old central heating oil burner that's been in the shed for years, though gas is quick and SO easy and a cleanish furnace atmosphere so no contamination, BUT I only work in Non Ferrous. One of the MOST important issues and often overlooked in non ferrous is the need for accurate temperature control – many casting defects start here ! To that end a dip pyrometer – an inconel sheathed K type thermocouple and a handheld readout remove one of the many variables in this game ! I spent over 5 years reading before I did anything and when I did I met with success that spured me on ! Noel.

[PatJParticipant @patj87806]

There is something magical about pouring molten metal in a sand mold, and then breaking out the casting.

I know it is an ancient process.

As Noel says, temperature is all important when pouring aluminum (I use 356 alloy aluminum), and I pour at 1,350 F.

I heat the aluminum as fast as possible, with an oil burner that is often 12 minutes for a #10 crucible of AL, making sure not to overshoot, and then pour immediately.

If you wait around with hot aluminum, or overheat it, it absorbs gas like a sponge.

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Edited By PatJ on 02/07/2022 12:47:24

[noel shelleyParticipant @noelshelley55608]

Hey Pat, sounds like you read the book I never wrote ! Noel.

[PatJParticipant @patj87806]

Noel-

I always like to discuss foundry topics with fellow casters, because no matter how much one learns about foundry work, there are many clever individuals who have better ideas and methods.

Learning foundry work is an ongoing process, and I think there is always room for improvement.

I know of one forum that has an informal "Foundry/Casting Manual".

It would be nice to have an open-sourced modern foundry manual that could be edited by multiple people, such as how wikipedia is handled.

I will look for a pdf of the foundry manual that was written by a ME while he was in school.

It is a somewhat decent overview of the casting/foundry process, but needs a few items added.

I would not take this as the final word on foundry information, but it is open source and free, and covers a lot of topics.

http://prometheus-foundry.com/tutorial.html

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[vic francisParticipant @vicfrancis]

Wow brilliant work, The only thing I would say is to avoid greensand for anyone starting out, just too difficult to get right, to dry or too wet which is dangerous! When I found the petrobond it was the way too go ,what a massive improvement over greensand.I added bentonite to the greensand but I found it to crumble however careful….the resin sands sound even better! Is it possible to use resin moulds with lost wax patterns? Or are you using the tradition investment plaster?

Great post Pat, / guys

Vic

[noel shelleyParticipant @noelshelley55608]

Hi Vic, If you had trouble with greensand then you needed the right type/mix of sand and also the right technique. I am using the same barrel of sand for over25 years, all I have aded is water ! With resin or petrobond there are waste, reprocessing and costs to consider. One well known supplier of castings etc for years insisted that I used lost wax to make a casting due to the finish until one day I showed him how it was done.

I would say GREENSAND, every time ! Easy to do , no special addatives, no waste, and no extra costs !

If your in the UK PM me and I will talk you through it, you won't look back ! The moisture issue is not a problem once you know how. Ask anyone who has seen me at the Midland show how easy it is and the good results that can be got from very simple kit. Look at the castings in my album. Noel.

[Andy_GParticipant @andy_g]

Posted by noel shelley on 22/03/2023 10:04:43:

If your in the UK PM me and I will talk you through it, you won't look back ! The moisture issue is not a problem once you know how.

I'd be interested in this, too – happy to PM, but it might be of general interest?

[Ady1Participant @ady1]

Great thread on a very rare part of the hobby. Cast Iron, wow.

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