Hello guys,
I vanished off the radar for a while, for some reason known only to its self i could not get into the site, however my computer geeky son in law found what I was doing wrong , Age & computers do not seem to harmonise (Or is it my advanced brain?) however back to casting problems, When in times not too far distant back when both Europe and the North American continent were much more industrialised foundry folks had recourse to some very fine products from sand quarries , Every foundry had its own sand blends to suit what they were manufacturing, What possibly suited the guys up the road were a little different from the products used by the foundry down the road, This was no doubt due to different sizes of castings, different casting temperatures and the interaction of different metal temperatures, and metal composition to the mould material, Added to this mix was methods of moulding in each shop, In some plants it would be machine moulding in other plants hand moulding.
however if one looked at the type of sand grains used, some sand grains would have differences, There would be round grains , angular grains , & sub angular grains, And compound grains, I.E. different shapped grains added through one another , this helped the sand grains to key together There also was natural clay deposits in the sands which went along way towards the sand grains being cohesive one to the other, Also say a steel foundry would use a courser grade of sand to allow permeability (spaces for the hot gases to eascape, A brass or bronze foundry would get away with a finer grade of sand for light work, to give a good casting surface finish, The same was true of light iron foundry practice
Think sewing machine castings, radiators for central hot water heating, and the extremely beautiful American clock cases , All in was'nt mother Nature wonderful?
however back to the average home craftsman using whatever he can lay his hands on Myself included, Kiddies play sand is lovely stuff, I have not the sand microscopes to examine the grains , But I would be ppretty certain that this nice sand would be round grain , thus each grain does not bind to its nature very easily, Taking your moulding practices , Should you only add water alone your mould would fall to pieces, As it has no strength.
Now we add Bentonite, this gives an artificial bonding medium, In other words we have made a synthetic sand, foundry folk have been doing this for many years with great success.
When blending your sand, add your Bentonite and get it well through your sand evenly, And add your water 4% to 6% roughly , you should be able to pick a handfull of sand and lightly squeeze it into a lump without it adhering to your hand Many years back I was on a particular line of work where i had to get the green strength of my sand upped a bit, In other words a bit stronger, The method used was this when making up my water to moisten my sand I made it quite hot, to it I added some Mollasses, Try this idea, But do not go berserk about a tablespoonfull of Mollasses to two pints of water is about right , if you add too much you will end up with a gooey mess or end up with a gassy metal finish to your castings
I ended up with a lovely sand which held its shape It was a nice pliable sand mix , Try a little for your facing sand, to judge if it is correct you will know how it goes through your sieve , . & also how your pattern draws and it should not stick on to your pattern, A good plant is to rub your pattern with flake graphite I used to do that all the time
many years ago I had to
I vanished off the radar for a while, for some reason known only to its self i could not get into the site, however my computer geeky son in law found what I was doing wrong , Age & computers do not seem to harmonise (Or is it my advanced brain?) however back to casting problems, When in times not too far distant back when both Europe and the North American continent were much more industrialised foundry folks had recourse to some very fine products from sand quarries , Every foundry had its own sand blends to suit what they were manufacturing, What possibly suited the guys up the road were a little different from the products used by the foundry down the road, This was no doubt due to different sizes of castings, different casting temperatures and the interaction of different metal temperatures, and metal composition to the mould material, Added to this mix was methods of moulding in each shop, In some plants it would be machine moulding in other plants hand moulding.
however if one looked at the type of sand grains used, some sand grains would have differences, There would be round grains , angular grains , & sub angular grains, And compound grains, I.E. different shapped grains added through one another , this helped the sand grains to key together There also was natural clay deposits in the sands which went along way towards the sand grains being cohesive one to the other, Also say a steel foundry would use a courser grade of sand to allow permeability (spaces for the hot gases to eascape, A brass or bronze foundry would get away with a finer grade of sand for light work, to give a good casting surface finish, The same was true of light iron foundry practice
Think sewing machine castings, radiators for central hot water heating, and the extremely beautiful American clock cases , All in was'nt mother Nature wonderful?
however back to the average home craftsman using whatever he can lay his hands on Myself included, Kiddies play sand is lovely stuff, I have not the sand microscopes to examine the grains , But I would be ppretty certain that this nice sand would be round grain , thus each grain does not bind to its nature very easily, Taking your moulding practices , Should you only add water alone your mould would fall to pieces, As it has no strength.
Now we add Bentonite, this gives an artificial bonding medium, In other words we have made a synthetic sand, foundry folk have been doing this for many years with great success.
When blending your sand, add your Bentonite and get it well through your sand evenly, And add your water 4% to 6% roughly , you should be able to pick a handfull of sand and lightly squeeze it into a lump without it adhering to your hand Many years back I was on a particular line of work where i had to get the green strength of my sand upped a bit, In other words a bit stronger, The method used was this when making up my water to moisten my sand I made it quite hot, to it I added some Mollasses, Try this idea, But do not go berserk about a tablespoonfull of Mollasses to two pints of water is about right , if you add too much you will end up with a gooey mess or end up with a gassy metal finish to your castings
I ended up with a lovely sand which held its shape It was a nice pliable sand mix , Try a little for your facing sand, to judge if it is correct you will know how it goes through your sieve , . & also how your pattern draws and it should not stick on to your pattern, A good plant is to rub your pattern with flake graphite I used to do that all the time
many years ago I had to
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