I think it might develop to an interesting discussion.
There's a guy suggest to cut a wire to improve the torque of the motor :
I trying to figure out if the wire actually need to be cut, or you just can power it like a bipolar and everything will be fine, like described in this link :
I've tried a code in the link and it works fine. is there any advantage to cutting this line ?
Cutting that wire depends on the step pattern you use with the motor. If you use a "wave drive" or "1 phase" sequence where only one coil is energized at any time then the wire does not need to be cut. The individual in your video/blog post is using a "full step" or "2 phase" pattern where both coils are energized at the same time and thus the wire needs to be cut. You'd need to peek at his code to see that.
You may need to be quite careful about sequencing your H-bridge - winding A needs completely disabling
before powering up winding B and vice-versa.
When converting an unipolar motor to bipolar use like this you have to be careful not to exceed the power
rating of the motor - in practice you can only get about sqrt(2) more amp-turns for the same heat
dissipation. You will need a higher supply voltage.
If you want to use a chopper driver then you must separate the windings or it'll be a disaster.