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is obtained. Guide pins which materially lessen the skill required are provided on some snap flasks (Fig. 12). The Vpin on the drag is machined inside to fit the guide on the pattern plate and the ear on the cope is made to bear on the outside of the drag flask pin. This arrangement makes drawing the plate a very simple operation and insures a perfect draw.
Lifting Devices There are several devices on the market for mechanically lifting the cope off the plate and then lifting the plate off the drag (Figs. 13 and 14 show one of these devices). This method insures a perfectly straight draw without skill and patterns having a deep, straight draw can be produced much quicker and surer by using this method.
These pattern drawing devices are built into the machine and operate by a hand lever forcing the pattern lifting rods upward through the table. They first engage the cope and
lift it from the plate. When the cope is clear from the pattern the rods engage the plate and lift the plate from the sand (Fig. 14). The plate can now be removed and cope lowered into place. The mechanical lifting or pattern drawing devices are a great help to the hand squeezers. They remove the skill from drawing the pattern and make an unskilled man equally as proficient in drawing the pattern as a skilled mechanic.
Another device has lately been put on the market. This device consists of an aluminum frame inside of which the patterns are attached (Figs. 15 and 16) as in the regular vibrator frame. At each corner of this frame is a cam resting on the edge of the drag flask. These cams are operated by means of a single lever. By raising the lever the cams lift the cope, and the frame and pattern from the mold. .
Cope and Bottom Boards The cope board should consist of a good substantial planed board made 74" smaller each way than the inside of the flask and fitted with undercut battens. A metal button should be attached to the cope board to locate the sprue hole. Bottom boards should be 14" smaller each way than the inside flask measurements and should not be used when they become badly burned. In molds that require little peining, time is saved by putting peining strips around the outside edge of the boards. These strips are triangular in shape about 1/4" high and 34"
on the side next to the board. These peining strips serve to squeeze the sand much harder around the outside of the mold and make peining by hand or shovel handle unnecessary. Metal bottom boards are used in some foundries and have the advantage of lasting much longer than wood boards. These metal bottom boards are provided with lugs to insure even squeezing
Flasks The snap flasks should be the best obtainable. They should be well made and rigid, with good hinges and catches. Old, loose jointed “wobbly” snap flasks are not ones that will prove profitable.
If the mold is one that will probably require bands when poured, tapered flasks are much to be preferred (Fig. 17). Many bad castings result from crowding tight or ill-fitting bands on snap molds.
The tapered mold receives the band without crowding.
Sizes of Flasks As a general rule 12" x 18" is the largest snap flask that is profitable on a squeezer and 10" x 18" is a better size. If the flask is only 8" or 10" wide, it can be as long as 24".
In square sizes, 14" square is about the limit, and again one 13" square will give better results.
12" x 14" and 12" x 16" are good workable sizes.
Much larger sizes of molds can be squeezed but as a rule you are limited by the weight of the mold a man can carry without having it come in contact with his body, for if it touches the man while being carried to the floor shifts are almost certain to result. In hand molding the board extends beyond the mold and will do no harm if rested against his body.
As the number of patterns in the mold has no influence on the number of molds made, it is a distinct advantage to have the mold as full as possible.
Vibrators The use of vibrators, while not absolutely necessary, is certain to increase production. The vibrator is fastened to the plate or pattern frame and operated by a knee valve so both hands are free. This insures a good draw and no broken edges to patch. Vibrators are operated by both air and electricity, and one or the other is now available in most foundries. While the electric vibrator is of recent introduction it has been giving satisfaction and no hesitation may be felt in using it where air is not available. The electric vibrator can be attached to the ordinary light socket and be operated by a knee switch. Sprue Cutter A good tubular sprue cutter should be provided for each machine. Using an old bent sprue cutter that holds the sand, making several attempts necessary before the sand can be dislodged, is not economy. A piece of brass tube the proper size makes a good sprue cutter. PLATE PROJECTING
PIN LUGS BUILT OUT Y INCH
Teaching Laborers As referred to in a former bulletin, the best plan is to teach laborers to operate the hand squeezers. A good molder will only operate a squeezer when no other job is obtainable and will never do justice to the machine. The instruction of the laborer should be undertaken in a thorough manner. He should be instructed in being clean and neat about his work, to dump all imperfect molds and not try to patch them, to keep the sprue hole clean from loose sand, to blow off or clean the plate or pattern, to keep the hard-sand match clean from sand and to put his tools in their proper places. Have convenient places provided for all tools. Teach him to make as few motions as possible. He should be taught to make the mold in the most economical way. By studying the machine and the job it is often possible to cut out one or two motions.
The most important thing is to instruct him properly on the pouring. Most work produced on squeezers is light and can easily be lost in pouring. He should be taught the necessity of keeping the sprue full, how and when to cut in pouring