For flat head keyhole cut scissors failure problems no lines, according to the author many years of operating experience analysis, we can proceed as follows to deal with:

If less than a flat head keyhole cut on the line, then check on the cut line when the knife on the cutting line, is not aligned on the line. In addition, the hair cut on the line and see if we can still tucked on the line to ensure no dropped calls.

It is worth noting that we have to look at the scissors tune the position of the lever on the cut line loosen two screws, and then after adjustment.

There are two position two screws below the baseline thick, thin (we all know, is applied to a thin thread sewing materials operations, the thick line is mainly applied to thick material sewing jobs), adjust the alignment of its on-line cut line.

After adjustment, we have the two screws on the cut line control rod tightened again, then I believe that "less than cut line" this failure phenomenon can be easily ruled out.