1) x1 to be used where no other indications are made in product standards or on drawings.
2) x2 to be used where a short thread run-out is required for technical reasons.
3) a1 to be used where no other indications are made in product standards or on drawings.
4) a2 to be used for slotted and cross recessed head screws and in cases where a short distance is required for technical
reasons.
5) a3 to be used for screws assigned to product grade C.
6) Tolerance h12 for screw threads up to 3 mm nominal diameter.
7) Type A to be used where no other indications are made in product standards or on drawings.
8) Type B to be used where a short thread undercut is required for technical reasons.