Thanks for posting that

I would argue the need for degassing tablets. I did some casting at evening school some 40 years ago, we degassed the metal and the resulting casting was full of bubbles.

Over the last few years I have produced approximately 40 castings in aluminium at home and have not done anything to degass the metal. None of my castings have shown any bubbles. when machined.

Whether you degass or not have a go at casting it is very addictive! It also can save you a lot of money, I am currently building a rotary table and the cost of materials if built from bar stock was over £40 but with castings the only real cost has been the fuel for the furnace and that is under £5.

Edited By norman valentine on 08/09/2014 08:46:02

Hi Graham,
One warning you missed out although you show that you have the paving blocks covered was not to work directly on concrete as it can explode if molten metal is spilled on it. I have tried using stainless steel containers and they do only last a short time. I think they dissolve slowly in molten aluminium and start to leak. I have seen it recommended to heat them for a time to form a good layer of oxide on the surface before melting the metal in them. I think it is a good idea to post information on techniques like this to tempt people into trying them.

David, I used the recipe for home made refractory in "Mikesworkshop" in my small furnace and it works very well. I don't know if it would stand the temperature required for casting brass or bronze.

Les.

Mike, many thanks for the heads up greatly appreciated. I was under the inpression they were similar. When I can get to the back of the garage I will check to make sure just what I have. Cheers David

Hi Graham,

My understanding is that one should not use Borax as a flux with Aluminium, an equal mixture of NaCl + KCl should be used.

Peter.

Graham, you mentioned casting Lead, the pot looks a bit grisly so the best clarifying material for lead is Bees wax!

A piece about the size of an Acorn and stir the lead as the heavier metals go down and stirring mixes the metal and brings up all the dross. Plus all the steel bits from the scrap. You know how to skim off the dross leaving clean metal.

I wonder if the risers for Aluminium need to be quite large to add pressure to the pour? Maybe that is why the corners did not fill out?

Clive, (my only forte is lead bullet casting.)

You can of course cast lead in high temperature RTV silicone rubber moulds which arguably give far better results plus you can make multiples from the same mould. The ceramic filled (red) rubber is the one to use.

Edited By Chris Trice on 09/09/2014 00:31:43

Clive

Ditto on the bees wax. An excellent lead flux that has been used in bullet casting for centuries. Years ago I cast thousands of bullets for obsolete cartridges using a combination of plumbers lead and wheel weights. The wheel weights hardened the bullets which greatly reduced leading in the bore of the rifles. I initially used a Coleman naptha camp stove for a heat source which melted the lead in very short time. An 8" tall piece of 6" well casing with a 1/4" plate base welded on made an excellent lead pot. Later I purchased a commercial bullet casting electric lead pot that eliminated the need for a dipper but took far longer to do the melt. Always worked outdoors in a good cross breeze using a respirator to keep from inhaling the fume. Despite all my precautions, I gave it all up when I asked my Doc for a Pb test and the results came back on the high side – 56 whatever that means. At the time I was employed in a paint shop as a sign painter using lettering enamels that contained lead so it is difficult to say which activity caused the high lead count.

Bill

I obtained my castings supplies from a firm called Foseco way back. I never had a sign of pourosity using their degassing tablets over many years, and the sand was Mansfield sand. I did not like the oil bound sand as it was smelly, got burnt and a lot was wasted. One or two pointers were omitted from the description. To prepare the sand water is added until a squeezed handful of sand will just fall into two halves. If it stays together it is too wet. If it crumbles it is too dry Split patterns are easier to use than doing it oddside and useful for repetition. After placing the drag upside down on the moulding board, sifted with parting powder from an open weave bag. Half patten placed in and sifted with powder from an open weave bag. I then used a household cooking seive to seive sand until the pattern was covered, then I just chucked handfuls of unseived sand until half the box was filled then a gentle ramming with a broad rammer. I always got an excellent finish to the castings by seiving. Drag then fully filled, rammed. and "strickled" with a straight edge. Box reversed, pins located, gates cut with a tiny trowel made from tinplate and top box located. A little rubber blower used to remove surplus sand around the pins. Also used to get rid of any unwanted sand inclusion inside before closing up. Sharp edges to be removed as far as posible from the in and out gates to using forefinger, to stop the molten metal washing sand into the cavity. Cope and top pattern put in place, sifted with powder, filled and rammed. When boxes are opened a cavity is cut below the runner to form a little reservoir, and the top opening is tapered out to make a funnel shape and help pouring. To remove pins and pattern, the pattern is "rapped" to loosen then very carefully lifted out. The runner and riser can if necessary be extended upward with tubing to give a better head. Boxes should have peripheral key strips inside to stop collapsing of the sand. You may note that commercial boxes are fluted for this purpose. A leather apron and gloves are useful for safety and a full face visor. I got good results at first with some old pistons broken up in a sack with a large hammer. I hope the additional pointers will help beginners and add to an excellenty shot listing.