Directions for Facing Mouthpiece.
In many instances a machine will squirt metal back of the disk if the metal is very hot. As a general thing, this is laid to the gas, but in nearly every instance it will be found that it is caused by the mouthpiece not being true with the back of the mold.
In some cases it will be found that the mold is warped slightly, but not often.
If the back knife does not trim the bottom of the slug perfectly the metal will adhere to the back of the mold, making high lines (i. e., lines over .919, as explained under Fig. 39), and also prevent good contact between the mouthpiece and mold, which would, of course, cause metal to squirt back of the mold disk.
To prevent this, the mouthpiece should be faced up true with back of mold, as follows: First send a line through the machine, stopping at casting point; then screw up the nut on end of pot lever eyebolt until it touches the pot lever. This takes up the pot pressure, so that when the vise is let down the metal pot will retain the same position as when casting a line. Then disconnect the vise-closing jaw screw connecting rod by taking out the wing pin on end of vise-closing jaw lever. This will prevent the rod from being bent or broken when vise is let way down.
Then let the machine finish the revolution. Now throw off the driving belt and pull out pot pump plunger pin and turn machine by hand to casting point, disconnect mold disk slide and pull out disk B (Fig. 34); thoroughly clean back of mold A (Fig. 34) and cover with red lead mixed with oil, or it will be found much better and easier to use prussian blue oil paint, a tube of which will not cost over 10 cents.
Fig. 34.
Rub the back of mold with this paint; push disk B in until the back of mold A touches the mouthpiece X (Fig. 34); then turn mold disk back and forth, rubbing the back of mold over the mouthpiece. The blue paint will thus be transferred to the mouthpiece, and show the high points.
Should the paint show on one end only, throw the metal pot around by means of set screws to be found in foot of pot legs until it is about true: then, with a small coarse file, file off the blue spots, which are the high or uneven places. Then push the mold in once more, and again rub mold on mouthpiece and file off blue or high spots as before. Continue this operation until the paint shows in small spots all over the mouthpiece.
Before finishing this operation be sure to put in the cross vents between the holes with a cold chisel, making them a little deeper at the top, as shown in Fig. 35. This will prevent porous or spongy slugs.
After connecting the machine up again, put on the driving belt and run through another line, stopping, as at first, at casting point. Then let out the nut on end of pot lever eyebolt until it is about ⅛-inch from back of pot lever.
Fig. 35.
If this is done as described there will be a perfect lockup on the mold both back and front, the only metal trimmed from back of mold being that from the vents.