An industrial sewing machine may need to have the timing adjusted if it skips stitches or if the needle breaks during stitches. Adjusting the timing essentially re-syncs all the parts of the sewing machine. You can adjust the timing in just a few steps, but prior to handling the needle or any other parts, disconnect the machine from the source of power.
Unplug the sewing machine. If the foot pedal utilises a separate plug, then unplug this device as well.
Remove the faceplate, which is the metal or plastic piece that can be found just below the needle and foot, by unscrewing it with a screwdriver. On personal sewing machines, the faceplate just slides off, but most industrial sewing machines have the faceplate secured by screws.
Turn the hand wheel, which may be labelled as a balance wheel , carefully in a counter-clockwise direction to loosen the needle. Adjust the needle bar so that its mark aligns with the mark on the needle bushing. Then re-tighten the hand wheel by turning it clockwise direction.
Align the hook blade with the needle. To do this, first remove the position bracket of the bobbin case holder. Remove the 3 screws holding the rotating hook and the bobbin case holder. Turn the hand wheel counter-clockwise until the lower timing mark on the needle bar is aligned with the needle bar bushing. The point on the needle bar should be centred with the lower end of the needle bar bushing as precisely as possible. Now the point of the hook should meet the needle centre.
Turn the hand wheel counter-clockwise again, this time to test the timing of the bobbin and the needle. The timing is correct if the needle dips into the bobbin with a clearance in the range of .004 to .01mm. Replace the 3 screws to secure the rotating hook and the bobbin case holder.
Replace the faceplate by screwing it back into the groove with the screwdriver.
Reconnect power to the sewing machine and test by sewing a small scrap of fabric.