Possibly? I was thinking the patterns may have flexed a little as I rammed up the cope, but the long flats do not appear bowed. "Interesting" is one word for it; the one I chose only had 4 letters... Was hoping not to have to touch those 45's beyond a quick touch with a file just to remove any high spots. Jeff
Interesting but only because they're NOT mine. Had they been mine, my word choice may have been similar to yours.
It would be "interesting" to see if the same thing happened if the 45 portion was the same thickness. The same thing happens when I'm hard-soldering a mitred 90 in brass, or even welding in stainless. Have to make the mitres 45.1deg., or "stretch" them after.
A table saw or chop saw will fix that quickly. Frustrating, yes. Easily explained—-not by me. Dunno. Denis
Not sure I understand; I believe the 45's and the flask walls actually are the same thickness across most of the pattern, just not where the sand retention ribs are, on the upper and lower edge of the inside surface of the flask sides. Someone suggested to me that the 45's might need to have similar ribs added to keep them from warping due to shrinkage. They shared an image they had handy to illustrate what can happen to castings with no ribs: The long flat part of my castings didn't bow like that, but again the pattern does have ribs along the top and bottom edge there. Those ribs are absent from the 45's, which did move in the same direction as the 90's in the diagram. Could this be the issue? Ribs could be added to the drag side of the patterns (on the outside of the flask without them being in the way of anything, but I'd rather not have to. I also think maybe I poured it a little hot, which I think could maybe cause this effect to be more exaggerated, or cause it to happen in the first place. Since others have used the same 3D files and not had this issue, I'm tempted to try again with a bit cooler metal before I go adjusting the patterns. Table saw, eh? Great idea, thanks Denis. Jeff
I don't see the point of such long lugs on the corners. My own version has sides 15mm thick and gives an adiquate bolting face of 19 mm and much easier to cast. They are a joy to use and not heavy.
Yep, a normal carbide tip blade goes through aluminum like butter. A word of caution though, the chips it throws are pretty nasty so, appropriate PPE is a must!
I find a little cutting oil prevents chips from welding to the teeth of the blade. It only takes a few drops spread along the cut line with your finger . I cut aluminum carefully on a sled and guard against binding and slinging of cut off pieces. I also avoid standing in line with the blade so as to not catch a cutoff at 60 Mph—-the average velocity of the teeth on a 10-inch blade. I saw a guy get a nasty cut right at his elbow (antecubital fossa) from about a 1.5” triangular-shaped piece of 1/4” Al cutoff a table saw slung at him. Could have been serious had it severed the artery there. I cut it often but try to just use good sense to avoid “eating” a piece. Denis
I can see your cast flasks are working great for you Myfordboy. I never miss a video and would have been happy to try out your design, but I'm not ready to give up the fixed alignment pins. Partly because I fear the small loose pins you use making molds on the floor would bounce off the bottom board to fall and get lost in my molding bench's sand bin every time I pushed them out from above as you do. If anyone else, like me, hadn't realized it until just now, there is a thingiverse link to myfordboy's 3d flask files in his video description. Jeff
2nd try they pulled a little cleaner. Tried to pour these ones a little cooler to see if it makes the weird shrink(?) go away... Bedtime now. I'll cut the gating off and see if they make a square corner tomorrow. Jeff
They're not only nasty, but hot too. I always clean any sawdust from under the saw before cutting aluminum. Pete
Last 4 sides for the first flask are molded and ready to pour, later today. The 2nd pair was also not quite square, but they were closer. Upon closer inspection, it seems like it is just the far ends of the 45 sections that are a little fat on the mating faces causing them not to fit right. I'm going to try a little filing, out just past where the drill guide holes are, to take that part down a bit and see if the rest of those 45's will then fit square. If not, my neighbour offered to help me try and set them up in his chop saw for a teeny little trim. Jeff
Still needs the pins and alignment holes drilled and installed, but it's finally taking shape. I belt sandered the ends of the 45's a bit where they were a little too fat or something, so the corners fit together square now (almost) when they are bolted together tight. The cope sits on the drag nicely, without wobbling. If I can get the alignment holes done properly later today I expect it will be a usable flask. But this has been a lot of work for such a small flask... I look at the small cheap chinese one casting per mold half cast iron flasks that aren't much smaller than this and have the vertical pour option, and I can't help thinking, just 2 castings per complete flask instead of 8 would have been much easier to crank out flasks with, in a fraction of the time. But assuming the pins do work out, it seems like this might be a good way to make bigger flasks than this one. Jeff
Haven't read all of this thread so I may be duplicating work/files. Attached are files of my rendition of the flask patterns of Olfoundryman's work. They are reverse engineered from the published *.STL files in SolidWorks. I've included the *.SLDPRT so anyone can modify as needed/desired.
Olfoundryman left some comments about improving the 3d model in a reply to a comment I left on his latest video, fyi: Jeff
