when creating a sand casting mold using the 2 halves method (I'm not sure of the technical terms) how do you make sure that the 2 halves properly align?
Either pins and bushings or wedge blocks mounted to the cope and drag. Here's an example thread. http://forums.thehomefoundry.org/index.php?threads/simple-flask-construction-plus-other-tools.727/ If you search flasks in the Foundry Tools and Flasks sub forum you will find more examples. Best, Kelly
I'll just mention another way. The above is a classic method for a reason---it works and is pretty easy. I align the cope and drag of my flask using just a couple very short 1/2' or 3/6 steel pins in the DRAG and corresponding holes in the cope. The pins usually are placed toward each end on the near-side rail of the flask. I like that arrangement better than the more common palcement in the short end rails. I often use 2X 4 or 2X6 material for the sides and cut with shallow rabbet joints at the corners and screw them together with 2 TimberLOK screws in each corner. The pins protrude only a half inch or so and are domed to make alignment fall into place. The short pins work fine if there are not bits of sand or pattern that extend from the cope into the drag. In the non-protruding case no real guidance is needed once the cope lifts off the drag. I try to avoid pins protruding from the cope as they can tend to plow through the sand if the lift is not nice and level and clean. Just one of many ways to do it. If lift guidance needs to be straight up for a ways, I use longer pins and make sure there is adequate clearance so the pins don't tend to hang up. If you try to just drill two 2" deep holes into a couple rails and use 2" long pins, the lift will tend to hang up if you get just a tiny bit out of level. So, you will need some clearance in each hole. Maybe I'll take pics of a way around that problem. Denis
Miles, if you are talking about a split pattern, I drill through one side with the parting face half down on the drillpress table so I get a perpendicular hole. I use a forstner bit so it cuts clean, then I clamp the other half to the first with small stickouts and support the pattern on blocks. I taper the dowels slightly where they enter the second side holes and trim off the excess or fill any void with Bondo. I prefer loose pins so when I open the mold the pattern stays in its respective mold and can be rapped and drawn without damaging the sand. A little sanding on the taper achieves this release. If you have a surface parallel to the parting this can be done in a single operation.
Here are a couple pics of the stubby steel pins and holes that I use when practical. Yes I put flashing on my wood flasks to reduce coal-gas-related combustion. Denis
I don't know what flasks are other than a way to sneak liquor into concerts. I'm talking about when you cut the foam mold in half and pack the sand around both halves separately then rejoin them before the pour.
The patterns usually have some way of locating the two halves together. Most use dowel pins. The flask (two piece wooden box) also uses some way of locating the two halves together.
Using the right terminology helps. There is a lot of it and you're new, so no worries. Here's the deal: Flasks are the boxes we make molds in. For sand casting usually it is 2 boxes that fit together and packed full of molding sand which contains clay binders; for lost foam casting it is usually a bucket of loose dry clean sand with no clay. Patterns are the shapes we copy in metal. Styrofoam patterns are used for lost foam casting and wood or something else that is hard and durable is used to make patterns for sand casting. Molds are flasks full of mold material (ie. the sand), with a sprue hole on top leading down into pattern shaped cavities inside that we pour metal into. It sounds like you're asking about a split pattern, not a mold. I think you are mixing up aspects of lost foam casting and sand casting though. I never heard of a split pattern used for lost foam casting or a foam pattern used for sand casting. Does this help? Jeff
Oh, one of the videos that I watched the guy used flasks, he cut a foam skull in half, packed the sand around the skulls and joined them together. Admittingly it was a highly edited video and with my ADHD I probably wasn't paying %100 attention. Thanks for the vocabulary lesson, it should help a lot.
Dave Gingery's The Charcoal Foundry is cheap and very helpful for the bare beginner. Kindle or dead tree. It doesn't matter if you use charcoal or not. You won't be sorry. Pete
People on youtube do all kinds of crazy things that might not seem crazy until you've been doing this for a while. That said, he might have been doing a thing called 'full mold casting' which combines lost foam and greensand. It actually is a thing, I just forgot because I haven't seen it for so long! General consensus around here seems to be that loose sand works fine without stinking up your nice molding sand. Molding sand packed tight around the pattern would also make it a bit harder for the vaporized foam gas to escape the mold cavity through the sand... On the other hand it may be more forgiving if you bobble the pour as the mold should not collapse if you let the sprue drain out. It could work. Make sure to take lots of pictures of how you set up the mold if you try it, I don't think anyone here has posted about full mold casting before. Jeff
