To set the timing on a standard home sewing machine consists of two parts. The first is setting the needle bar height. Most sewing machines have two marks on the needle bar which are visible when the needle bar is at its lowest point. The upper mark should line up with the bottom of the of needle bar bushing when the needle bar is at its lowest point. The lower mark should line up with the bottom of the needle bar bushing just as the hook passes above the needle's eye on the upstroke. Turn the hand wheel toward you until the needle is at its lowest point. check to see that the TOP line on the needle bar lines up with the bottom of the needle bar bushing. If not most machines have a hole in the faceplate through which you can access the needle bar clamp. Insert a screwdriver through the hole or remove the faceplate. loosen the needle bar clamp a half turn. Needle bar should now be loose. Tap the needle bar up or down to line up the mark with the bottom of the bushing. Tighten needle bar. Remove throat plate and feed dog. The feed dog is the little piece on the bottom with teeth that moves the fabric through the machine. The throat plate is the plate that covers the feed dog. They have two screws each. At this point you may remove the bobbin if you wish but it is not really necessary. You will be able to see the rotary hook at this point. The rotary hook is the assembly that picks up the top thread and carries it around to intertwine with the bottom thread creating the stitch. Turn the hand wheel toward you turn past its lowest point until the lower line on the needle bar lines up with the bottom of the bushing. At this point the tip of the hook should be just above the eye of the needle. If it is not, it must be rotated until it is. Tip sewing machine back exposing the underside. The hook is attached to the lower shaft by three setscrews. Loosen two of the screws all the way, leaving one screw holding the hook assembly. Loosen the last screw SLIGHTLY leaving it holding the hook loosely on the shaft. Again turn the hand wheel toward you past the lowest point until the lower line on the needle bar lines up with the bottom of the bushing. Rotate the hook until the point of the hook is right above the eye of the needle, assuring that the clearance between the hook and the needle is kept at or near zero. Tighten all three screws on the hook assembly very tightly. Replace feed dog and throat plate. To check to see if timing is right; thread needle and turn hand wheel toward you one full turn. If the top thread picks up the bottom thread you have set the timing correctly. If it doesn't repeat process starting with needle bar height adjustment.