Sand Riddle (sieve)

When I started out with my foundry I had to find a way to sieve the sand used to make my green sand. At first I used kitchen sieves and fly screen or shade cloth. These worked OK, but I needed something finer too get better results, and make it easier to sift larger quantities of sand. I made a rectangular frame out of timber, open at the top and bottom and hung it to a frame with small chain. I then made an angle iron frame to go around the bottom and hold the fly screen in place. The idea was if I wanted to change the size of the screen, I could remove the frame and fit finer or courser mesh. Once it was suspended by the chain it was a matter of shaking it back and forward to sift the sand or powdered Bentonite. I used this for some time, but it became a bit tedious shaking it by hand, also I needed something finer still.

       I happened to come across some very fine stainless steel mesh that was just what I needed. I don't know what size mesh it is as it is too fine to count the wires. The sand is nearly as fine as dust when it is sifted, finer than beach sand. I then decided there had to be a better way to shake it than by hand! Basically I needed some way to shake it with a motor. I found a 12v car heater motor, a car water pump bearing and a suitable weight to mount off-centre so it would shake the sieve. I made a wooden mounting for the motor and water pump and joined the motor shaft and water pump bearing with rubber tubing and a couple of clamps so there would be no sideways force on the motor bushes from the weight. I then bolted a plate to the pulley boss of the water pump and bolted a weight (old cast iron pulley) on the plate to the side of the bearing. When the motor turns, the sieve, which hangs on four small chains, shakes the sand through into a plastic tub below. I then had the idea to put a ply wood top on the frame that supported the sieve and use it as a table in my foundry. This is now bolted to the wall and the sieve and tub are under the ply wood top which is now used as a bench beside my moulding table. All it takes is a bit of thought to find ways to make better use of things you make. Sometimes these thoughts don't happen until you have already built something, and then you have to modify what you have already done to make it better! Below are some photos of the sieve showing how it was built. Next I will describe my other sieve which is designed loosely around a sand riddle used in foundries. This is used to sieve and fluff up the green sand after it has been through my muller.

     

         This is the frame for the sieve with the ply wood top I added later.

This shows the sieve itself with the angle iron frame to hold the mesh.

Here is a view of the top showing the motor mounting.

View of motor mounting with coupling to water pump bearing and the pulley I used as the weight.

The sieve mounted underneath the bench by four small chains, one on each corner. The chains are attached to the bench by small "D" shackles so the sieve can be removed to clean out the residue.

Front view shows the chains, "D" shackles and the opening for the sand.

Side view with the plastic tub for catching the sieved sand.

Front view with the tub in place. The sieve hangs into the tub so it will catch the sand as it is sieved, but the tub can be removed by tipping it up to clear the sieve.

It has been quite a while since I last posted on my blog due to lack of time and other things I have been doing. I have changed some of my equipment since I was last on here, including experimenting with waste oil burners and just recently homemade K-Bond casting sand. As a result of the WMO (waste motor oil) experiments, I have built two new oil fired furnaces, and will post details of them and the K-Bond sand later on. I will now continue on from where I left off and describe some of the larger items I have made.

Ball Mill
              When I first started out in metal casting, I was unable to get powdered Bentonite to mix up green sand. I was able to get granular Bentonite from a local rural supplier (it is used in cattle feed supplements) but had to find a way of turning it into powder. Some people on YouTube used blenders or coffee grinders to process granular Bentonite into powder, but I found although this worked, it was slow. I also tried an old corn cracker I had (used to crack corn for chicken feed). This is basically a couple of  serrated rollers that the corn passes through and has a large flywheel that was turned by hand. This worked better than the blender, but the Bentonite had to be put through several tines to get it fine enough. Also it was bloody hard work turning the handle. After thinking about the situation some more, and some research, I decided a ball mill would be the way to go. A ball mill is usually a drum shaped container containing ball shaped weights and the material to be broken down. This is then rotated slowly and the balls break down the material as they rotate in the drum. I had a suitable drum with a clip on lid, and made a frame to suit with a washing machine motor and pulleys to gear it down. I mounted the drum on four small wheels from the hardware shop and run a belt from the lower pulley around the drum itself, which gave the final reduction in speed needed. I couldn't find any suitable balls to use, but found some heavy cast iron weights that would do the job. It was then a matter of putting the Bentonite in with the weights,closing the lid and turning on the motor.
The longer it was left on the finer the Bentonite became. This was the easiest method I found to reduce the bentonite to powder. I also used the ball mill to mix up the clay and sand to make my green sand before I built my muller. After shaking out my moulds, the lumpy green sand was also put in the ball mill to recondition the sand. It could also be used to then mull the sand by adding the required water to the sand. This worked OK in place of a muller, although the green sand tended to stick to the drum. It was still better than using an electric drill and stirrer, but not as good as a proper muller.
            The only problem I have had is that the drum I had was a bit rusty and developed a couple of holes.
Also the drum is a little thin and the "balls" are pretty heavy so they tend to dent the drum. This hasn't been too much of a problem, but if I was doing it again, or using it more often, I would use a thicker drum. Maybe a section of an old hot water tank would work well. The thicker drum would probably help the bentonite break down quicker, as the balls would not dent the drum as they turned. Below are some photos of the ball mill and they should be enough to get an idea how it was made and give someone enough info to make something similar. I basically made it up as I went along and probably the only thing to watch is that the drum doesn't turn to fast as the balls will tend to turn with the drum. It must turn slow enough so the balls roll over the material and break it up.

This is the ball mill as it was first constructed with a steel drum turning on caster wheels.The motor is run to a counter shaft and the final reduction is achieved by running a belt around the drum itself. The drum is only a steel drum the same as oil or paint drums, it is only thin and has some small holes. 

             This side view shows the drive belt around the drum,
the caster wheels the drum rotates on, the chute that sends the contents into a container and on the ground are the cast iron weights used to crush the contents.

 This is the rear of the ball mill showing the counter shaft  using an old washing machine pulley. The belt around the drum is tightened by a air conditioner jockey pulley out of a car. The ply was put on the bottom of the drum to cover some holes.

This is a shot with the drum removed showing the A/C jockey pulley for tightening the belt around the drum.The electric motor is pivoted to tighten the counter shaft belt.

These are the cast iron "balls" used in the mill. They aren't quite round, but do the job!

This is the gas bottle I cut to make a new drum for the mill. The old drum was too thin, and had some holes that I couldn't fix. A thicker drum should work better as the balls will be working against something more solid.

Here is the new drum, the bottom of the gas bottle with a plate welded on the cut end, and a hinged door to add and remove the contents.

Here is the plate welded on to the end of the drum, the opening will be closed by a hinged door.










This is the door in place. It is hinged on the top and is held closed by a bolt welded to the outside of the drum and a tongue welded to the lid.

Here is the lid open showing the bolt and tongue for holding it shut and some felt glued around the edge to seal it when it is shut.

Here is the drum mounted on the rollers. I had to find a shorter drive belt and shift the rear rollers to level up the drum as they run in the groove in the drum.

Here is a side view showing the mounted drum and the rear wheels in the groove. This helps to keep the drum from shifting when it is turning.

 



The other side of the ball mill. All it needs is a coat of paint to tidy it up.










Next up I will feature the sand riddle (sieve) I made to sift my sand. I have two different ones, one does the sand for my green sand and is very fine, and another to screen the sand after it has been mulled to get it ready for use. Hope this will be a little quicker than my last post.

Foundry Tools Part 2

Foundry Tools Part 2

Cast iron crucible lifting handle

Here is part 2 of my foundry tools section.On the left is the crucible lifter I made to suit the cast iron saucepan I am using as my new crucible. The tongue on the end fits into the slot on the saucepan and provides a positive point to rotate the crucible for pouring and the "s" shape stops the handle from slipping out. The loop on the bottom slides down and locates over the handle to support the other side when lifting and pouring.

Handle fitted to crucible

On the right is the handle fitted to the crucible. The handle on the side provides leverage when pouring the metal into the flasks. To use the handle the tongue is slid into the slot and the handle lowered and the loop is slid over the handle of the crucible, to release the crucible the loop is slid back and the handle raised to release the tongue. The crucible is held securely at all times and cannot slip and spill hot metal everywhere.

Crucible sitting in furnace

           

The next photo shows the crucible sitting in the furnace. The support is designed to hold the side of the crucible with the loop and allows the tongue of the handle to still be inserted.The other side has a square handle fitted with a block of steel on the bottom that sits against the side of the furnace to stop the crucible from slipping off the support.

Steel crucible sitting in furnace

 On the right is my steel crucible in its support in the furnace. The crucibles are held up this way for two reasons. The air is fed in from the bottom of the furnace and so the crucible cannot sit on the bottom, and as I am using wood as fuel, there has to be space under the crucible for the wood. The next photos show the pouring handle for the steel crucible. Again I wanted something to hold the crucible securely without the chance of slipping. I devised an over-centre lever to lock the arms on the pins on the side of the crucible when closed. To release the crucible, the lever is released and a spring opens the arms far enough to clear the pins and release the crucible. This handle has been modified to fit the larger steel crucible as the original crucible was smaller. This involved making up some longer arms to go around the bigger crucible and bolting them into the holes that fitted the small one. Two pins on the arms fit into holes and stop the arms from turning when the crucible is lifted.A nut was welded to the bottom of the crucible so a hook could be used to tilt it to pour the molten metal.

Arms open to fit to crucible

Arms closed

Handle closed on crucible

Hook used to pour metal

A couple of fire pokers

Selection of tongs

        
Above we have a selection of tongs. The ones on the left are used to hold the hot casting by the sprue to remove the sand. The BBQ tongs are handy to place metal in the crucible without splashing hot metal around.The next set originally had straight jaws,but were bent down and extensions welded on  to grip my steel crucibles to place them in the furnace. The last ones are end nippers used to remove flashing (sharp edges where the drag and cope meet around the pattern) The photo on the right shows a couple of fire pokers. The thin one was my first one and was easily bent, so I made a stronger one.

Skimmers

Here we have several skimmers for removing the dross (slag) from the top of the molten metal. Two of them are old forks fitted with long handles, the other is a steel plate with holes drilled in it welded to a long rod. The forks are not the best as they are stainless and as can be seen in the photos, are starting to dissolve. The steel one works better, but the rod is too thin and bends when the dross is bumped off. I recently made a more substantial one out of thicker steel and this works well.

New skimmer

New skimmer

 Here are a couple of photos of the new dross skimmer I made. The head is made from a piece of angle iron shaped to match the side of the crucible and has holes drilled in the base for the molten metal to run through. The handle is some 10mm square steel I had at the time, round would be suitable as well. The handle at the top was made in a loop so it was easier to control when scooping out the dross.

Green sand stirrers

Modified paint stirrer

Next we have some of the tools I tried for mixing green sand and conditioning it again after casting.These were all used with a 12mm electric drill with a gear reduction low speed. Smaller quantities may be able to be done with a smaller drill, but it is pretty hard on the drill. Of the three designs the leas effective is the centre one, which is just round rod bent to shape. Next I bought the paint stirrer on the right from a hardware store. It worked better, but the drill had to be run in reverse or it just pulled out of the sand and it didn't break up the lumps very well. I then welded on the two thin metal wings as in the second photo, and this improved it again. After some research I made the one on the left out of round stool with a bar welded on the bottom. I added wings to each end and sharpened the leading edges, This one worked the best of all, but it was still hard on the back bending over using the drill. I then decided to make a sand muller to reduce the back strain, but at a pinch you could get away with something similar to the two better ones to do your sand mixing.

Sprue cutters

In gate cutters

 On the left are a selection of sprue cutters. These are just lengths of copper tubing which are pushed into the sand to cut the sprue (opening to feed the metal into the mould) The plastic ones were out of an old cistern vale and are tapered. The end of the pipe can be sharpened to cut the sand better. On the right are some in gate cutters made from old spoons. These are used to cut a channel to get the metal from the sprue to the pattern. I have since made better ones shown in the next photos. These were made by folding some thin metal around suitable round rod to make a "U" shape. Then a handle was cut out of wood and shaped to suit, and attached to the "U" shaped metal with a small metal thread bolt.

Metal and wooden handle

Metal bent into "U" shape

Metal fitted to handle

Top view

3 different size cutters

Small sand sieve

On the right is a small sand sieve I made out of PVC fittings and a metal trivet from a camping store for sieving the sand into the mould to cover the pattern. The trivet was cut to fit inside the PVC cap and is held in place when the other fitting is screwed into it. The centre was cut out of the cap , leaving the "O" ring and its seat in place. A handle was made up out of some aluminium tubing and bolted to the side with metal threads. A PVC cap can be placed on top to keep the sand in when it is shaken. I have found that the trivet doesn't make the best sieve due to it basically being flat steel drilled full of holes. Sand seems  to go through wire mesh better, especially if the sand is damp. I have since replaced the trivet with fly screen mesh and the sand will go through this better. If I can find some more suitable mesh, I will replace the fly screen and it should work better again. A normal cooking sieve can be used as well, although the mesh is fairly fine in those too. The use of PVC fittings is still one way of making a small sieve, and could be made simpler and cheaper by using a glue on cap and piece of PVC pipe rather than threaded fittings.

Trivet cut to fit in PVC cap

PVC cap cut to suit

Bottom of sieve

Inside sieve

Completed sieve

Sieve with  handle and cap

Following are a few of the miscellaneous tools that I use when doing my foundry work. Some can be made at home or purchased cheaply.

Various sand scoops

Water spray bottle

The sand scoops are used to shift sand around and the spray bottle is used to add water to the green sand. Both are cheap enough to buy but the scoops can be cast if you desire.

Fillet tool

Dross skimmers

On the left is a rod with a round point used to smooth filler to make a radius on joints in patterns. They can also be made by attaching a suitable ball to the end of a rod. On the right are a couple of potato mashers that could be used for dross skimmers.

Rack for muffin trays

Muffin trays

 Left are the muffin trays I use to pour metal into ingots for future use and on the right is one of the racks I sit the trays on when pouring ingots. These are old shelves out of a stove or fridge and stop the wooden bench from burning.

Muffin tray and rack in use

Some moulds ready to pour

 Well that is about all the small tools I use in my foundry at the moment I will post updates if I find any better ones or make modifications to improve them. Next I will look at the larger items such as the sand muller, riddle and ball mill. If anyone has a question or would like more details on anything I've done, please leave a comment and I;ll try to help. Also the photos can be enlarged for more detail by clicking on them.