Sewing machine repair is an exciting and satisfying career , but it is also a great hobby or business. While, repairing sewing machines is not for everyone, it can be lots of fun.
At first, fixing sewing machines can be an overwhelming task. There are so many different makes, models, and designs to learn. When you look at sewing machines, they may all look alike. As soon as you start taking off the covers, you discover just how different they really are. The hook assembly is one of the things that every sewing machine user should and every technician must understand.
There are two basic types of hook assemblies: The Rotary Hook assembly and the Oscillating Hook assembly. Each type has its own features and benefits, but they both do essentially the same job.
The Rotary Hook Assembly includes a hook that moves in a complete circle round and round. The hook slides behind the needle, and proceeds all the way around the bobbin carrier until it again slides behind the bobbin carrier. Singer sewing machines revolutionized the sewing world with their drop in rotary hook systems.
Where do you put the bobbin on this machine? I could be inserted in front, or top under the needle plate, or on the left end of the machine. If it is a top loading bobbin, the machine is usually a rotary hook machine.
If the bobbin is inserted in the left end of the sewing machine arm or on the front face of the sewing machine arm, it may be either a rotary or oscillating hook.
It is easy to tell the difference. Rotary hooks rotate around the bobbin carrier in a continuous circle again and again. Oscillating hooks move to half way around and then go back to start again. The go back and forth ” back and forth.
So to make sure what you have just answer this one question. Does it go all the way around as a rotary does, or does it go part way and retrace its path to start over as an oscillating machine does?
Watch closely. The point of the oscillating hook starts just a few millimeters to the left of the needle when it reaches its lowest point. As the needle rises, the hook moves behind the needle. A loop of thread forms in the small cut out on the back of the needle running above the eye called the scarf. The point of the hook grabs the thread here and pulls it around to the bottom where it releases the thread. It then oscillates back to its original position for another stitch. Bernina used their special patented CB Hook to become a premium sewing machine line.
As far as the user is concerned, it does not matter a lot whether the machine has an oscillating or a rotary hook. Both systems achieve the same basic result. The pick up the thread from the scarf of the needle and pull it to wrap around the bobbin thread.
Each part must work in perfect timing and coordination. The hook assembly and needle must reach their exact connection point on every stitch precisely when as where they are suppose to. This is called hook-needle timing. When they are out of synch or time, you will see skipped or potentially no stitches formed at all.
There are several ways to adjust the hook needle timing depending on the sewing machine. Some adjust the position of two interlocking gears immediately below the hook. Some must be adjusted at the right side of the lower shaft where the lower shaft joins the vertical shaft. Some must be adjusted by adjusting a timing belt. In all cases, the key is to cause the needle and hook to meet at the right time in the right way and form stitches.
The more you learn about how sewing machines work and how to repair them, the more sewing machine repair you can do. Just think there are millions of sewing machines just waiting to be serviced by somebody. You could be that somebody.
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