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A creative metal worker can work wonders with molten  metal. It matters not whether your aim is to create art castings, repro antique parts, remake vintage car and motorcycle parts, vintage oil engine parts, or special one off parts for a unique project. You will need to know how to build quality, low cost equipment & tools. And learn & understand the reasons behind the how & why foundry work is carried out. If you are eager for success and want to learn how to build and set up your own hobby foundry, then Click Here Now. To read and learn more about metal casting.

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Making Timber Patterns.
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   Lotus 26R Brake Caliper Mounting Plate Project.

       
Image 1: Above is a two-part RTV mould with backing support boards and rubber bands used as mould clamps, when making the RTV moulds, a pouring sprue is made at the top of the RTV mould with a short round 1/2" rod. As always, feed to the heavy part of the casting.                        

       
       
Image 2: Kahfil - (Bondo) patterns, and matching plaster follow boards for each pattern, which are coated with several coats of shellac.

 
       
Image 3: Pattern & plaster follow board placed face up in the drag ready for the moulding session to begin. Note the draft angles on the four edges of the plaster follow, and around the edges of the pattern, this is done to allow the plaster follow to lift cleanly as shown in the image below.               

         
       
Image 4: Ramming of the mould is complete, the follow board is removed, and the mould is prepared for the next step. The Brass pins inserted into the back of the follow board are lifting pins. Note that flask register pins are now facing upwards ready to accept the cope flask. You may ask why I prefer a steel flask to a timber item, steel flasks are robust and will take a hammering without getting out of register.
They are quite easy to make, we include a "How To Make Mould Box" instruction ebook with the hobby foundry ebook package. If you can weld, you'll be able to make them for just a few dollars worth of steel, and they will last for many years, I made a set of four, they have been in use for many, many years, they dont owe me a penny.                                     

RTV - Kahfil (Bondo) - & Plaster.

Have you discovered the wonders of RTV silicone & kahfil (Bondo) products yet? The project above was made pretty easy by using these products, the RTV was used to make an exact replica pattern from an original damaged casting, the plaster was used to create a follow board which allowed the difficult shaped pattern to be easily moulded and cast in green sand.

Before you begin making your pattern the first thing you need to do is purchase a package of two-part RTV 585 silicon compound & curing agent. The RTV mould is best if it is carefully made in two halves, as in image No 1. RTV requires an overnight cure before the second part can be made, when the second half is being made a coating of vasaline is smeared over the cured RTV before the second half is poured, the pour has to be done carefully to make sure that no air bubbles are entrapped in the RTV otherwise they will cause problems further on. If you are unfamiliar with this product and want to learn more about it, we include a free instruction ebook on how to use it with the hobby foundry ebook package. The RTV silicon product will allow the production of a new pattern in a fraction of the time that a new timber pattern could be made, it will save you time and money.

Image No 1:  Displays the split RTV mould, note the nice clean edges and surfaces, if the RTV is poured carefully it will flow and fill every little nook and cranny of the pattern, the particular object being cast is a brake calliper mounting bracket for a classic Lotus Élan 26R. The original mount plates were badly damaged, so before new ones were remanufactured the old ones were repaired and beefed up somewhat to upgrade the strength and integrity of the new castings, the building up was done with kahfil or body filler, and then carefully filed and sanded off to the correct shape. When everything looked right, several coats of grey surfacer primer was applied to get a smooth surface with a minimum of imperfections.
Once the RTV impressions were taken from the master pattern (The original) were cured, the backing boards were placed either side of the RTV mould halves and bound with rubber bands in readiness to pour the diluted kahfil (bondo) to create a set of new production patterns.

Image No 2:  Shows the result of two successful kahfil pours, the kahfil or bondo is diluted with styrene monomer to a creamy consistency, the correct amount of hardener is added and thoroughly mixed in then the kahfil is carefully poured into the RTV mould, just like you would with molten metal into a sand mould, but slower to avoid air entrapment. The mixture requires an over night cure, but when they have cured the kahfil body filler patterns are quite robust, but don’t drop them as they will break. The plaster follow boards shown with the patterns in image No 2 were made to make the job of ramming up the sand mould easier, as seen in the other images, the plaster follow boards simply act as a holding saddle, the follow board is removed at a later moulding stage. Note the bevelled edges of the follow board, the bevelled edges allow easy withdrawal of the follow board from the sand mould. The orange colour is from the several layers of shellac that have been applied to the plaster to help seal the surface from moisture attack. The follow boards could be easily made from the kahfil mix also, but at the time we were happy with the plaster follows, and yes, they need to be handled with kid gloves, because as you well know plaster is brittle. You will also notice that the drag box is shown with pins down, this will be rolled when ramming is complete.

Image No 3 & 4: The ramming is complete and the box (flask) has been rolled over, the follow board was given a light rapping before two 1/8th wire rods were inserted into predrilled holes to enable the follow to be carefully removed from the pattern and drag mould. The follow must lift cleanly with out moving the pattern or any snagging on any of the moulding sand. Parting dust (graphite powder) was applied to the sand mould and pattern, the cope box was placed down over the drag box register pins, a sprue and riser stick were placed into the small holes visible on the lugs (Image No 4) and ramming proceeded us per normal, before the cope was rapped and lifted, the venting of the sand mould was done. RTV can be a real saviour at times when it is not possible or economical to make a new pattern, the fact that modifications and alterations can be done on a broken original pattern is certainly a bonus with this system, it is a little fiddly, and it may take two a three days to carry out, but hey, we are only hobby workers, so time is not a problem is it? As mentioned above, we supply a free ebook with the hobby foundry ebook package outlining how to use this wonder product.

Sand Moulding Systems For Hobby Metal Casting.
For the benefit of new ezine subscribers, following is an article which provides an overview of sand moulding systems.

Metal castings are created in sand moulds, a pattern can be embedded into the sand, or the sand is rammed around the pattern.The patterns can be made from a variety of products.

Following is a brief description of those processes.

Green Sand.
One of the all time favourites because of its ease of use and predictable results. Green sand can also be stored and will keep moist for weeks in a household plastic garbage bin ready and waiting for the next moulding session. Green sand is the most efficient, low cost way for the hobby worker to start making moulds for metal casting. But the trouble with green sand is the need for a Muller to make your first batch. Green sand does require maintenance and looking after to get the best results, but it will last for many years for hobby use and can be used over and over again. Green sand is made up of; olivine sand, bentonite, a small amount of coal dust, it is a water based sand which makes it attractive for the hobby worker.

Co2 Gas System.

This also is an easy system for the hobby worker to use, it is frequently used in trade schools or colleges for foundry practice instructions because it can be carried out with fairley basic equipment, and small batches of moulding sand can be readily made up.
Generally it is quite easy to use, and repeatable results are not difficult to achieve. However there is one thing that can be detrimental to the Co2 performance and that is if any excess moisture is in the sand, moisture levels above 0.5% will impair the performance of the sand and give poor moulding results. One drawback with co2 is the rental cost of the gas bottles, and the expense of gas cylinder regulators required for correct gas line
pressure. Sand consumed in the moulding process is usually discarded after each use, which could present a problem if you are constantly casting.

The Self-Set Process.

The self-set system is also very easy to use, all you require is good Clean foundry grade sand, a silicate to mix with the sand and a catalyst to create the reaction in the silicate, which normally takes around ten minutes on a warm day.

The equipment required consists of a: mixer, use a small hand held power drill fitted with a simple paint mixer. And an accurate digital kitchen scale to measure precisely the chemicals you'll be using.

The chemistry is quite expensive to buy, and is supplied in 20 litre and 200 litre drum sizes, the hobby foundry worker may need to cultivate' a friendship with your commercial foundry man in your area.

There are several different systems that can be used and too complex to explain here. Suppliers such as Foseco have free info product user guide sheets to explain exactly how to use their products. The chemicals are generally quite safe to use as long as you follow the manufactures safety instructions, as you always should.

The EPS or Full Mould System.
EPS= Expanded Poly-Styrene

The EPS process resembles investment casting in that a single-part flask is used, so that no parting lines-and hence no fins appear on the finished casting. It is essentially a 'one-off' process, since the consumable pattern is carved from expanded polystyrene.
This is a polymer derived from benzene and ethylene, and in its expanded form it contains only 2 % actual solid polystyrene.

Readers will be familiar with the substance, which is used in the manufacture of ceiling tiles, and also as a packaging material for fragile audio  & electronic equipment. An expendable pattern, complete with runners and risers, is cut from expanded polystyrene, and is completely surrounded with dry clean sand in a simple box or can.

The molten metal is then poured on to the pattern, which melts and burns very quickly, (vaporises) leaving a cavity, which is immediately occupied by the molten metal. No solid residue is formed, and the carbon dioxide and water vapour evolved in the combustion
of the polystyrene do not dissolve in the molten metal, but escapes through the permeable mould sand as a gas. And does have a very strong odour.

Moulding can be achieved merely by pouring readily available clean dry Sea Sand around the pattern. As the polystyrene burns, it produces a tacky bond between the sand grains just long enough for a skin of metal to form.

This moulding system is used extensively in the engineering industries; the process is used in the manufacture of large press-tool die-holders, and similar components in the 'one-off
category. Casting tolerances come very close to that of the investment casting technique. This system can provide a wide range of applications for the experienced hobby metal caster.

Foundry Sand Core Production.

Cavities within a casting; as required for liquid cooling passages in engine blocks and cylinder heads, as well as many other applications are created with sand cores. Special core forms (core boxes) are used to produce sand cores. Simple core shapes can be made from oil bonded sand, a basic vegetable oil such as linseed oil can be used to make effective sand cores in the hobby foundry. Once the core/s have been made in the specially shaped core box, the sand core is baked and cured in an electric or gas fired oven.

Cores are inserted into the core print cavities which remain in the sand mould after removal of the pattern from the mould. Wherever possible, foundry patterns should be designed and made to avoid the use of separate cores, reducing the use of cores will reduce the mould set-up time and thus help to reduce labour costs in the foundry. But that is not always possible, and often a separate core is required.

With a completed sand mould at the appropriate moisture content, the box containing the sand mould is then positioned ready to fill with molten metal; I.e. cast iron, bronze, brass, or aluminium alloy.

After filling the mould with molten metal, the box is set aside until the metal is sufficiently cool to enable the removal of the hot casting from the sand mould. A rough casting is produced that, in the case of iron or steel, may still be glowing red.

When casting with metals like cast iron or lead, which are significantly heavier than the moulding sand, the flasks, called the cope & drag is covered with a heavy plate to prevent a problem known as mould floatation. Floating the mould occurs when the pressure of the metal pushes the sand above the mould cavity out of shape, causing the casting to fail. Sometimes mould box clips or flip locks are used to securely lock the boxes (flasks) together to prevent loss of metal due to the drag mould half floating.

After casting, the inner cores are broken up and removed with steel rods, or shot blasting and removed from the casting. The sprue and risers are cut of and removed from the rough casting. Various heat treatments may also be applied to relieve stresses from the initial cooling and to add hardness; in the case of steel or cast iron, this is done by quenching in water or oil.

The casting may be further strengthened by surface compression treatment such as shot peening, which adds resistance to tensile cracking and smoothes the rough surface, cast iron engine conrods & crankshafts are treated in this manner.

The above methods and techniques can be applied to the hobby foundry. Think about the application of using internal sand cores on your project, cores will help to reduce the amount of metal you will need for a pour, and simplify the machining processes required. Avoid heavy metal sections abutting next to thin metal sections as the heavy section will pull metal from the thin section during solidification.

Could You Imagine: Just adding water to your sand to make moulds and cores.

We hope to have more on this in the next issue.

The Wonders Of Foundry Work.

How many other metal working pursuits do you know of that give you the freedom and creativity that metal casting offers?

Think about the basics of the process for a moment.

#You take a little sand to make the mould.
#You can use a mixture of fuel gas and an air blast to create a high melting temperature using an uncomplicated mixing burner tube.
#Design & Build a basic refractory lined furnace to melt the metal.
#Scrounge some scrap metal to melt and convert into a valuable new metal casting.
#Build some quality foundry handling tools.

The foundry process is really not all that complex, the knowledge available today to the hobby foundry worker is quite amazing, if you possess other general metal working skills you will be able to build & construct almost anything that you require for your mini hobby foundry and create things that will simply amaze other people.

Fabricating things from metal is rewarding, but making things using metal casting techniques is truly creative, and can even be financially rewarding if you want it to be. If you are still thinking about what's possible with metal casting, then perhaps it is time to begin exploring, to find out what you can achieve as an individual metal worker, and if you need a hand to sort the wheat from the chaff then we can help you do that to, just check any of our ebooks out.

Have fun, be careful, and be safe.
Till next month.
Col Croucher.