I make an 8" casting that I sell to folks either as a raw casting or machined intended to be used as a short precision prism and straight edge to be used to recondition ways of lathes, milling machines and the like. Until now I have been using wooden flasks to cast it in pairs and the wood works fine, but it eventually burns up after use 20 or thirty times. So, I cast some simple aluminum "boards" and welded them together. Since the way this mold/flask system is used involves no extension of the pattern above the strike off of the flask, long guide pins are not needed. The flask sides and ends are "I" beams in cross section though the flanges are only 3/8" wide and the webs are 1/4" I use quite short 3/16" pins in the flanges to provide alignment of cope on cheek and cheek on drag. And I use tabs to secure cope to cheek and cheek to drag. I also use bottom and top boards for security when flipping the flask/mold. This is to keep the pattern from falling out of the sand and to make sure the sand does not fall out. I secure the top and bottom boards using 1/4-20 flanged button head screws and I use the same screw to secure the tabs. I use one screw type as I drive the screws with an impact driver (gently) and using one screw diamter and head type requires no bit changes in the driver. I decided to bypass the potentially more versatile bolted connection of flask components to each other. I expect to use these same flasks in their current configuration for a good many years and think it is unlikely I would want to mix and match flask components. Welding considerably simplifies casting and joining and results in a very stable joint. I used welded joints, short pins and tabs in larger flasks I made for a larger casting and like the system very much. Enough blabbing, here are some pics. The assemble flask with top and bottom boards. (I could have been fussier about making the segments fit more precisely. But, they will function just fine as is. I'll be making another flask set of this size and probably will pay more attention to making each segment more precisely match the others in dimension.) I am going to use a lifting "bobbin" as an attachment point for the spreader bar on my hoist. The assembled flask weighs about 90 pounds. So, I flip it manually and lift sections manually. But lifting the assembled mold to the floor in a controlled fashion is a strain. The hoist takes care of that. The bobbin is counterbored so that a turned-down flange screw fits into the counterbore and I, again, needn't change bits on the driver. The tab from inside the flask. The tab aids in aligning the flask sections too. End view of assembled flasks. Bobbin not in place. Milling the paired and already pinned flask sections using a right angle head on my mill. I used the right angle head to drill the holes for the flask tabs as well. I tapped the holes using my battery-powered drill motor. Extra flask pieces to be assembled into another flask set after casting some more long pieces. Note ends are just squared-off. No attempt made to make miters for assembly with bolts. FWIW, Denis
I can see a line of luggage able to withstand airport baggage handlers made like this . They look great, I'm suitably jealous already.
I took the new flasks out for a spin today. Weather was marginal, but snuck in a melt between showers and 38 deg weather. The flasks worked well. I will add finger grip bars though. These will be wooden 1/2 x 3/4" wood bars screwed onto the front and rear pieces of cope, cheek, and drag. Very easy to do. This will make handling when opening and closing the mold easier. I found gripping the full flasks more difficult than necessary as the sides are so smooth. Pics tomorrow. The lifting "bobbins" worked well. Denis
I did add grips to the cope and drag. Very simple pieces of fit cut with a 10 degree relief angle on the down side of them as they will be lifted. That really helps my fingers get a solid feeling grip even though the wood is only 1/2 thick. I did ease the edges with slight radii as well for comfort. I used screws that are self-drilling and then used an angle grinder to trim off the protruding drill portion of the screw. Quick and crude but the grips really help in handling the flasks. In the future I do not think I will try to incorporate such grips into the patterns for flask sides, but will just add wood grips as needed. FWIW, Denis
Kinda new here so if this is a question that can't be asked just delete it. Denis where can one look at/purchase your prism and straightedge?
You certainly can ask. I sell them when I have them in stock on eBay. And sell directly to individuals. Look for Foster Featherweight Straight edge or casting on eBay. I have to work to maintain stock. denisgfoster@gmail.com
