Casting gun metal

[DalboyParticipant @dalboy]

Has anyone cast gunmetal from old castings.

If so,

1- how much heat is required and do you need a furnace to do so.

2- do you need to add anything to it to get a good cast.

3- what is the best casting sand to use.

Is there anything else to take into consideration beside the obvious safety equipment

 

[noel shelleyParticipant @noelshelley55608]

YES I have ! BUT make sure IT IS gun metal NOT brass. You will need a pouring temp of 1100c, MAX 1150c. You WILL need a furnace and crucible and the other gear that goes with it. I use crushed charcoal as an aid to keeping oxygen out of the melt and Mansfield sand, though a fine sand and bentonite clay mix will work. What are you trying to cast ? Do you have any experience of casting or at these temperatures ? IF NO to either of the questions then a good start would be Foundry work for the Amateur, or The back yard Foundry, from the workshop practice series.  Good luck Noel.

[DalboyParticipant @dalboy]

Thank you, Noel. I do have both of those books, I will go through them again. What I want to melt and recast are some cylinder castings from a Rob Roy (not the two for my loco, but a pair I messed up and some which I ordered that were no good which they did not want returning after replacing them).

I am looking at casting a cylinder for a stationary steam engine, but that is a little way off, but I am starting to do a little research first.

I will be making my own patterns and need to check on how much larger they will have to be made but one thing at a time

 

[JasonBModerator @jasonb]

The other option that I have used when recycling old cylinder castings is not to melt and recast them but use them as a source of hollow bronze/GM. Depending on the casting you can also make use of the chest as either a new chest of an end flange for the typical shape of a stationary engine cylinder.

Only costs you a bit of silver solder and propane rather than a foundry set up.

 

[noel shelleyParticipant @noelshelley55608]

Jason gives you an interesting option ? Adding the core prints is easy  but for the core proper use a piece of pipe, thin wall, split down the side with a hacksaw. Close it up with a pair of jubilee clips, ram up then slide off the clips, it will spring open and your core will slide out ! Simple. Noel.

[JasonBModerator @jasonb]

Ah you do make it sound easy Noel, wish a bit of pipe would do for this I’ve just drawn.

Pattern

Cores in the sand

Should come out like this with cast water jacket, exhaust port and the cored bore which has tool run out space and a tapered end down to a smaller diameter

[noel shelleyParticipant @noelshelley55608]

Having had the pleasure of working in Bridport Foundry I was using resin bound sand for cores, very strong but easily burn out ! That looks as though it will be fun to mold. For the cylinder core 2 bits of steel, weld/tack together, bore out, to suit core then cut tacks and use resin sand. You make beautiful drawing look easy, every man to his own ? Noel.

[JasonBModerator @jasonb]

That one is down for 3D printed patterns & core boxes and being done in iron, all 27kg of it according to the CAD. Bit of reverse engineering for an early full size Gardner, about 11″ long and 4″ bore.

[DalboyParticipant @dalboy]

Thanks for all the information. Jason I will look at them and see if that is possible for what I want

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