Snap-flask
The Encyclopedia of Founding (1892)
Besides the common snap-flask made at most foundries, there are some very excellent devices made for this purpose by the several patentees. One is an adjustable combination wood and metal snap-flask that can be adjusted to a variety of sizes. The wood parts of the flask are the pieces to which the hinge is attached, and also the parts to which the latch is fastened. The steel pieces are the inside lining. The wood and steel pieces are fastened together with bolts, and by means of a long slot the flask can be spread to the desired size. The wood is 3/4-inch cherry, and the steel is 1/8-inch. It is provided with a spring-latch, making it easy to open and close. Similar flasks are made all steel, having the same adjustment. Making them of the latter metal has suggested the round steel snap-flask, which is very light, and requires much less sand than the square one. For all who desire to manufacture their own snap-flasks, trimmings, including latches, hinges, and pins, can be had of infinite variety. Latches are made of malleable iron, with flat, oil-tempered steel spring. When the flask is closed the latch makes a solid locked corner, and it is so placed that by pulling latches together with finger and thumb of one hand, the flask opens freely. Hinges are made with the view of obviating any pinching of sand while closing. Any number of adjustable pins may also be had which can be perfectly fitted in a few moments. See SNAP-MOULDER. Snap-moulding is bench-moulding; but instead of using the customary iron or wood flasks, the moulder is provided with a "snap-flask," inside of which he rams all his moulds, carrying them to the floor, when completed, one by one, in order for casting. When the snap is removed a flat weight holds it down. A hole in the weight permits the metal to be run down the sprue and pouring all off, independent of the usual surrounding flask. If the sand walls are not able to withstand the pressure exerted when the mould is poured, a light iron band answering to the form of the snap is rammed within it. By this method the moulds are sustained like any other flasked ones, the difference being that the light iron bands are not pinned together. See SNAP-FLASK; BENCH-MOULDER.
What Has Changed in the Last Century
The snap-flask described by The Encyclopedia of Founding in 1892 "the wood is 3/4-inch cherry, and the steel is 1/8-inch" is still a working tool, and the design has barely moved: a hinged four-sided frame with a spring latch at the opposite corner, stripped away so the rammed mould stands on the floor under a weight. What has changed is where such flasks are used. Bench snap-moulding of the kind described was once how a jobbing foundry made its small castings by the hundred; since the middle of the twentieth century that volume work has gone to machines, above all the vertically parted flaskless moulding machines pioneered by Dansk Industri Syndikat in the 1960s, which make and pour moulds with no flask at all, and to matchplate machine moulding with chemically bonded or no-bake sands. Snap flasks today are mostly the equipment of small jobbing shops, pattern shops and hobby foundries, and are commonly bought as aluminium castings rather than bolted up from cherry and sheet steel by the moulder himself.
Written for this edition, 2026.