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). [Illustration: FIG. 138. Chain-stitch machine. 1. Cloth Plate 2. Presser Foot 3. Needle-Bar Nut 4. Needle-Bar 5. Needle-Bar Screw 6. Foot Bar 7. Lever 8. Liftee 9. Take Up 10. Embroidery Spring 11. Pull Off 12. Spool-Pin 13. Spool-Pin Holder 14. Automatic Tension 15. Tension Rod 16. Ball Stud 17. Lever Stud 18. Connecting Rod 19. Small Wheel 20. Belt 21. Shaft 22. Frame 23. Stitch Regulator 24. Cap 25. Looper 26. Link 27. Feed Bar 28. Feed Surface ] Always regulate the stitch and the size of needle for each size and kind of thread used. A table for this usually comes with each machine, or is often stamped on the machine. Select the thread suitable to the material. The number of a needle is marked on the shank. Needles made for one kind of machine will not always work on another. An automatic tension should not be changed or meddled with. Some tensions must be adjusted to the thread. Follow directions coming with the machine for adjusting tensions. Remove any thread which has become entangled in the mechanism of the machine. Never use a bent needle. A bent needle drops stitches on a chain-stitch machine. Soaping the needle helps it to go thru goods difficult to penetrate. When a machine runs hard, it needs oil or has become gummed up with poor oil. When gummed, clean with kerosene oil. Thread or ravelings wound about the axles of the wheels also makes the machine run hard. Learn to use the attachments of your machine--take care that they do not become bent. The lock-stitch does not rip easily.