Melting Gun metal

[DalboyParticipant @dalboy]

Can gun metal be melted for casting without going to the expense of buying a furnace, as I feel for the amount of time I would want to do casting is limited to the odd time.

I have to failed casting (my fault) and another two which were not up to standard which I brought as replacements, Yes I did get free replacements for those later two.

[BazyleParticipant @bazyle]

Size is everything. There used to be kits for doing tiny amounts of lost wax casting in a microwave.
I’ve not tried but a regular set of brazing hearth parts and torch should make up an egg cup sized crucible furnace.

[DalboyParticipant @dalboy]

Thank you. I do own this little hearth and a calor gas torch with various nozzles including the biggest one, however I would need to upgrade my gas bottle as the largest I have at the moment is the 6KG size from when we had a caravan as well as the 3.9KG.

I am not trying to melt large quantities, just enough to make another cylinder for a future model. Not only that, but I can make a flask, but I would need to buy some casting sand.

[noel shelleyParticipant @noelshelley55608]

Only last week I smelted a load of zinc for anodes. I used the bottom half of an old gas cylinder (may be a 7Kg ) lined it with 1″ cramic fibre blanket, cut a tangential hole near the bottom to put in the end of a burner. An A4 crucible. The important thing to consider is the need for secondary air for the burner. Almost any metal vessel will do even a biscuit tin. I have melted brass at about 1020c by using 8 K23 bricks in a circle and a sievert burner. Small name plates were successfully cast.

In answer to the question –  YES ! For gun metal you will need about 1100*c +. Small items will need higher temperatures, solid lumps lower.

In 1995 I used a spindrier casing, salvaged kiln bricks, the blower from a hotpoint washer/drier and the variable speed unit from a hoover vacuum cleaner to build the furnace I still use. The burner was made from bits and had a 1.8mm nozzle. A pot of brass in about 20 mins bronze/ gunmetal takes a little longer.

Good luck.  Noel.

PS if you need more info just ask. As for gas bottles see the tread on silver soldering torches and the Bullfinch chart. N

[not done it yetParticipant @notdoneityet]

As per  Noel, anything is possible to self-build a suitable furnace.

If you eventually choose to buy, get a gas-fired example.  Vevor offer an electric furnace, but I somehow doubt it would last long if heated to its specified maximum temperature.  My Paragon Sc2 kiln, good quality – not like vevor – is rated at a maximum temperature of 1093 Celsius (surprise, surprise, an exact conversion from 2000F!).

Standing the gas bottle in a large bucket/small tank of warm water gets around the problem of reduced butane/propane evaporation (at this time of the year), btw.

[DurhambuilderParticipant @durhambuilder]

You can buy complete 6kg capacity propane furnace for little more than £70 on our favourite auction site. Not sure about safety standards but model engineers are a resourceful lot and well used to operating supposedly dangerous or hot items!

[DalboyParticipant @dalboy]

Thank you everyone for all the info. I do have time before I get around to it but at least I can get stuff together for this project.

I still have the Rob Roy to work on over Christmas as well as other little projects like a top and bottom for the surface plate so I can leave it out and not get it damaged, as well a couple of racks for the mill and lathe tooling.

[jaCK HobsonParticipant @jackhobson50760]

Air blower (e.g. hair drier) and coal or charcoal should get hot ennough. You need a crucible that will take the heat. Surround and cover the crucible with charcoal. This pot mender is melting iron https://www.youtube.com/watch?v=rzOgxx-YG8w

[noel shelleyParticipant @noelshelley55608]

If you go down the road of using coal (not a good idea), coke or charcoal then your on the way to making a small blast furnace. which is a lot of work. It will indeed melt iron but since we only need 1150*c not 1450*c propane is quick, clean and easy. When using the above fuels the cost of the proper crucible that is needed becomes an added cost to the job. Melting ferrous metal is a next level task compared to the non ferrous metals. It is not just the melting point that counts it is the super heat that is needed to pour the molds. 1450*c is white heat and needs very careful handling, certainly not for the faint hearted or the ill equipped. Noel.

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