Sand Core Making

[doubleboost]

Hi
Lads
I am about ready to cast the cylinder for my mill engine
The cylinder will be cast in bronze
It is a fair size so a central core will be needed to save on metal and make machining easier
The ingredients i use are
4 Parts silver sand
1 Part clean moulding sand
1 Part core binder (wheat flower)
Temperd (dampend) with molasses disolved in hot water


A piece of steel pipe is used for a mould (this is split full length and held closed with a couple of hose clips)

The dry ingredients are mixed together

The liquid is slowly added untill the mix becomes nice and fluffy

This is lightly rammed in to the tube
A 5mm rod is inserted through the centre (this helpes the core to vent)

The hose clips are releaded and the core gently pushed out on to a piece of steel plate

I only need one but i always make a few and select the best
The next part is best done when the wife is out
The cores and plate are cooked in the top of the oven at 200 deg C untill they stop smoking These ones took 40 minutes

Once cooled they should be hard and a bit crumbly
If they are hard like stone the mix was too wet and rammed too hard

A better core is obtained if linceed oil is used instead of molasses but this really stinks the house out
John