All sewing machine parts must be in harmony. If they are not, the machine will skip stitches or will not sew at all. Using blunt needles or fuzzy threads; incorrect insertion of the needle; and lack of maintenance, such as cleaning and oiling, can damage the machine mechanism. Sometimes industrial Singer machines, whether they are older or newer, need the adjustment called timing, which corrects interactions between the hook, needle and feed dogs.
Turn the balance wheel toward you and lower the needle into the needle bar as far as it will go. Remove the faceplate. Turn the balance wheel toward you, until the needle bar moves to its lowest point. The needle bar has two timing marks near its upper end. If the needle bar is not set at the correct height, loosen the screw in the needle bar connecting stud and move the needle bar up or down until the upper timing mark is centred with the lower end of the needle bar bushing. Securely tighten the screw.
Turn the balance wheel toward you and bring the hook point to the centre of the needle if the setting of the needle bar bushing is disturbed, and it is impossible to set the needle bar for the correct height. Loosen the screw holding the needle bar and move the needle bar up or down to bring the top of the needle eye 1/32 inch below the point of the hook. Securely tighten the needle bar screw. Loosen the needle bar bushing setscrew at the top of the machine arm. While the hook point is located at the centre of the needle and 1/32 inch above the top of the needle eye, move the needle bar bushing up or down to bring its lower end exactly even with the lower timing mark on the needle bar. Securely tighten the needle bar bushing setscrew.
Remove the slide plate, feed dog and bobbin case to determine that the hook is timed correctly. Remove the position bracket of the bobbin case holder. Take out the three screws holding the rotating hook section and bobbin case holder and remove them. Place a new needle in the needle holder and turn the balance wheel toward you until the lower timing mark on the needle bar is centred with the lower end of the needle bar bushing. At this point the needle bar should be on its upward stroke. The point of the hook should be at the centre of the needle.
Rotate the balance wheel and bring the three screws in the hub of the hook, one at a time, directly under the throat plate opening if the hook is not timed correctly. With a screwdriver, loosen the screws from the top of the machine bed. Turn the hook on its shaft and bring the point of the hook at the centre of the needle. Tighten the screws. The hook should be set as close as possible to the needle without touching. If the hook is too close to or far from the needle, loosen the three screws in the hub of the hook and the bushing screw and drive the bushing in or out, as may be required, until the hook just clears the needle. Be very careful, otherwise you may damage the bushing. Securely tighten the three screws and the bushing screw.
Set the stitch regulator for the longest stitch to correct the timing of the feeding mechanism. Loosen the feed eccentric setscrew and turn the feed eccentric until it is timed correctly. It should be timed so that the feed dog starts its feeding movement, away from you, when the needle bar starts its downward stroke.
Turn the sewing machine off during the adjustments.