The top of a filister-head screw (or a hexagonal socket-head screw) should not be flush with the top surface of the part, as In (a). This would require unnecessarily close tolerances for the head of a screw and the counterbore. A small increase of the depth of the counterbore (b) eliminates the need for the close tolerances.

Another similar situation: in the case of a two-diameter shaft (a), avoid the need to match both shaft diameters by adding a clearance, if possible, for one of them, as In (b).

The design of the hinge (a) involves several interdependent dimensions with fairly close tolerances. In design (b) the lower hinge is axially floating and in design (c) the width of the middle (rolled) portion of the righthand member has been eliminated. In designs (b) and (C) the operation of the hinge remains reasonably efficient, but the need for close tolerances has been reduced.

In the assembly of a plunger, (a), which is to exert pressure on the bottom of a hole and which, at the same time, must be capable of rotation, make the matching surfaces at the bottom of the hole flat (b) to simplify machining and leave a large clearance between the pins and groove in the plunger [as in (b)], so that the pins are not under pressure.