Stitching irregularities are often the result of incorrect thread tension.
Industrial sewing machines, for all their power and heft, are actually quite simple. Their design enables them to withstand extended periods of sewing with little downtime. Professional sewing shops can't call in a repair person every time a machine skips a stitch, so these machines are made to be easy to maintain by the sewing operators. While home sewing machines have numbered tension dials, most industrial sewing machines have simple tension adjustment nuts or knobs. A close examination of the stitches can easily identify which tension repair is needed.
Instructions
1. Remove the existing bobbin and replace it with a bobbin containing thread that contrasts with the top thread. This will make it easier to examine the stitch pattern. Check to make sure that the top thread follows the correct threading route for the sewing machine model.
2. Rotate the pulley by hand, putting the needle through a complete rotation to pick up the bobbin thread. Pull both top and bottom threads behind the machine and place them in the starting position.
3. Place a scrap piece of fabric beneath the pressure foot and sew a 5-inch stitch line. Remove the fabric from the sewing machine.
4. Examine the top side of the stitched fabric. If the contrasting bobbin thread is noticeable between the top stitches, the top thread is too tight. Turn the tension adjustment knob a quarter turn counterclockwise to ease the top tension. If the bobbin thread isn't noticeable, continue with the next step.
5. Turn the fabric over and examine the bottom side of the stitched fabric. If the top thread is noticeable or looped between the bottom stitches, the top thread is too loose. Turn the tension adjustment knob a quarter turn clockwise to increase the top tension.
6. Sew another 5-inch stitch line on the scrap piece of fabric to check the adjusted tension. Examine the stitch line to see if the top and bottom threads are sewing evenly. If not, continue to turn the tension adjustment knob in quarter turn increments, sewing a stitch line after each adjustment and checking the stitch pattern.
Tips Warnings
Accumulated debris between the tension disks is a common problem that interferes with proper thread tension. Many industrial sewing threads have lubricant coatings that enable the threads to withstand high-speed sewing. These coatings, often wax-based, can build up and prevent compression between the two disks. If adjusting the tension doesn't improve stitch quality, clean the disks by removing the tension adjustment assembly. The assembly consists of the tension adjustment knob, a small spring and two tension disks. Wipe the disks clean and reassemble.
