Fig. 136. Spool bobbin.
Fig. 137. Pulling up bobbin
thread.
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239. Chain-Stitch Machine. In the chain-stitch machine (Fig. 138), the shaft turns a device which draws a loop of thread thru each foregoing loop, thus making a stitch similar to crocheting, but having the cloth interlocked with the stitch. The needle carries the thread and makes it tight or loose as needed. The feed plate carries the cloth under the needle.
There is a tension to govern the thread. As a single thread is used in making this stitch, no bobbin is used. The tension must be tight enough to draw the loop of thread about the cloth, or else the thread will tangle.
240. Cautions for All Machines. Machines should be kept well oiled, and they must be kept free from thread and lint, for these are the things which give trouble in machines. Never try to draw the cloth under the needle any faster than it is pushed along by the feed plate under the presser foot. Pulling on the cloth bends the needle from the exact path which it should follow.
Move the treadle with a smooth, even motion—a jerky motion wears out operator and machine. Use only the best sewing-machine oil. Poor oil gums the parts of the machine. Clean the machine every day it is in use. Take care to set the needle in its proper position, and fasten it firmly in place.
241. General Instructions. Thread the machine exactly according to instructions. If not properly threaded, it will fail to stitch—the thread will tangle. If the bobbin is not properly threaded, it will not have the proper tension, and the machine cannot sew as it should. The bobbin thread will break if it is not properly threaded thru the bobbin case. It will also break if the bobbin tension is too tight (No. 14, Fig. 138).
