=233. Sliding Doors.= When sliding doors slip off the slide, they may be replaced. They are hung like a barn door. There is a metal track above the door between the walls. The door is hung on this track by pulleys which slide along the track. Sometimes, by accident, these pulleys are slipped from the track. The door then must be lifted so that the pulley can be set back on the track. Usually the door needs to be lifted but a fraction of an inch and then pushed a little to one side or the other to get the pulley into place. CHAPTER XXIII SEWING MACHINES [Illustration: FIG. 132. Lock-stitch machine. 1. Bed Slide 2. Presser Foot 3. Presser Foot Thumb Screw 4. Needle Clamp 5. Needle Clamp Thumb Screw 6. Needle Bar Thread Guide 7. Needle Bar Bushing 8. Thread Cutter 9. Face Plate Thumb Screw 10. Slack Thread Regulator 11. Tension Spring 12. Tension Regulating Thumb Nut 13. Tension Discs 14. Thread Take-up Spring 15. Thread Guide 16. Presser Bar Lifter 17. Face Plate 18. Pressure Regulating Thumb Screw 19. Presser Bar 20. Thread Take-up Lever 21. Thread Guide 22. Arm 23. Spool Pin 24. Bobbin Winder Stop Latch 25. Belt Cover 26. Bobbin Winder Thread Guide 27. Balance Wheel 28. Bobbin Winder Pulley 29. Bobbin Winder Spindle 30. Bobbin Winder Worm Wheel 31. Stitch Regulating Thumb Screw 32. Bed 33. Throat Plate 34. Feed Plate ] =234. Different Types of Sewing Machines.= There are two types of sewing machines in use--the chain-stitch and the lock-stitch. Sewing machines are made to run by hand, foot or mechanical motor power. This makes no difference in design or care of the stitching part of the machine. Motor and foot power run the machine faster than hand power. The treadle of the foot-power machines swings on pivots. These should be kept oiled and clean from lint and thread. The large and the small wheels for the belt should be oiled at the axle. =235. Lock-Stitch Sewing Machine.= A lock-stitch sewing machine (Figs. 132 and 133) consists of shafts and wheels which move the needle, feed plate and bobbin. The top thread is guided from spool to needle thru a tension so that only the needed amount passes forward each time the needle is raised after the thread has caught in the cloth. When there is a difference in the size of the thread used on the machine, the tension must be adjusted to fit the thread, unless the tension is automatic. If the tension is not properly adjusted or the machine threaded properly, the thread will either break, tangle at the needle point, or draw the top thread tighter than the bottom one (Fig. 134). A longer stitch is needed for coarse thread than for fine thread.