Why the thread cracked with when i sticked with the machine

Make sure that your thread is put through your thread tensioner (the two discs at the top of your machine) properly. Adjust the tension nut (the "wheel" sticking out from the discs, but not too tightly. If not done properly, the machine will not function.

Thread breakage is usually a thread tension problem unless the thread is rotten or defective, or there is a snag or blockage between the spool and the needle. There should be some sort of tension adjustment. Check your user's manual for proper threading procedure.

try using a pair of tweezers or wire pliers to get the thread

pull the thread thru the needle about 3 inches .. lift the foot .. place the thread under the foot exiting toward the back ..hold on to the end of that thread ... turn the sewing machine by hand one turn .. that will loop the top thread around the bottom thread .. now use a screw driver or stick or what every you have. slide it under the foot and out the back .. both threads will now be sticking out the back .. pull a little out (you may have to turn the machine a little to release the threads) .. now when you see both threads sticking out the back under the foot you are ready to sew ..

the tension must be too tight or check to make sure the spool does not have a crack that is catching the thread in the middle of using the serger. When the serger is working and the spool has a crack it catching the thread then you press to go on and it gives a break the needle because the spool is still holding onto the thread

Only two possible problems are :
1) The needle is not vertically straight anymore. It might have bent due to some collision or mistreatment. So, solution for this is very easy & cheap too. Simply, make it straight by some pressing & applying proper force OR buy a new needle and then it won't hit the rotatory arm.

2) Most probable problem is that the motor which drives the needle has lost its alignment. I hope, in this problem it will not hit at the correct point & will work imperfectly also. So, for solution purpose you will need to open your fav. ZIG ZAG yourself and will have to fix the alignment of that motor.

I hope things will work out for you soon by any of the above solutions...

Please rate this solution if it was helpful to you. Thanking you.

With Regards,
Shyny

Is the hook you are referring to on the needle plate (stitch finger) and the stitches form around it or does it move side to side while sewing (looper).
If thread is hanging on the fingers on the plate there is probably a rough edge that they are sticking on. You may also have a crack in the plate that is not allowing the fabric to go through and the stitches stack up. Remove the foot and check for a crack in the plate. With the foot on you won't be able to see it.
If hanging on a looper, it is out of position or you may be threaded wrong.

Put the bobbin on the short metal stick on top of the machine. Unthread the machine. Put the spool of thread on the tall, left side stick on top of the machine. Take the thread and wrap it counter clockwise around the circular, short, metal thing on the left side of the top of the machine, only 180 degrees. Thread the thread through the hole in the bobbin (which should be on top). Press the bobbin to the right, into the little white thing. Pull the turning wheel on the right side of the machine out. While holding the end of the thread, softly press the presser foot so that the thread goes around the bobbin a few times. After that, cut the end down to the bobbin. Now, press the presser foot down and wind the bobbin until it stops on it's own.

There are some different bobbin cases for different machines but the one you have is a pretty common one with a finger sticking out on top. If you examine the bobbin case you will see a slot on the side of it and there is another piece of metal screwed onto it. This is the tension they are describing.
To thread it properly, turn the bobbincase upside down and insert the bobbin in the case so you can see it. Place your thumb on top of the bobbin and pull the thread through the slot on the side of the case and under the piece of metal(the lower tension) which I described to you earlier.. When you have done that, remove your thumb from the bobbin and pull on the thread. It should have some tension on it.
Next,placing a thumb or finger on the bobbin to keep it from falling out, turn the bobbin case over.
Keeping the finger sticking up lift the lever on the
front of the case and insert the bobbin and bobbin case onto the spindle inside the hook assembly(The part that is in the bottom of the machine that turns when the hand wheel is turned.) Don't worry about the thread that is sticking out.
Holding the upper thread under the presser foot ,turn the handwheel towards you until the top thread pulls the lower thread to the top. Pull the thread to the left of the machine, insert your fabric, lower the presser foot and begin sewing
One more thing , The finger sticking up on the bobbin case will go into a slot on the ring holding the hook inside the machine.
Hope this solves your problem.
Be sure you thread the upper part properly. It should go through the tension, then the take up lever and then the needle. Tension should be set at around 5
sewman7