=24. Steel Hinge Butts.=—In recent years, the =steel hinge butt=, which is shown in Fig. 15, has been substituted for the cheaper cast-iron butts. The better grades are made with ball tips, as indicated in the figure, and these are now almost universally used for medium-class work and for the better class of interior work. Owing to the fact that they are made up with smooth surfaces, the steel hinge butts are adapted to the various buildings and finishings without grinding or buffing. These butts are stamped and formed by machinery, so that their cost is reduced to a minimum; they can be sold for less than cast-iron butts, and also possess the advantage over the latter in that they are practically unbreakable. The ordinary grades are not suitable for large and heavy entrance doors that are constantly in use, for they are made of soft steel and wear readily at the joints. Thus, in time, they will allow the door to sag and thereby necessitate readjustment, or the planing of the door at the sill. For such class of work, steel hinge butts should be used that are provided with ball bearings, as shown in Fig. 16, or with hardened-steel washers inserted at the joints, as shown in Fig. 17. These steel butts are also made in smaller sizes, and for bookcases, cupboard doors, and light work of this kind in ordinary building operations, they are used almost exclusively, having practically forced the small cast butts for this class of work out of the market. [Illustration: FIG. 18] =25. Cast-Bronze and Brass Butts.=—All types of =brass= and =bronze butts= are made in several grades and qualities, and it is difficult to determine the grade after they have been placed in position. It is therefore advisable for the architect or building superintendent to make a careful inspection of this hardware, to determine whether it is furnished according to specification. Brass and bronze butts are made in light, or commercial, heavy, and extra-heavy grades, and in all cases should be steel-bushed, self-lubricating, and provided with five knuckles. The high-grade butts are now manufactured with ball bearings at the wearing joints. The construction of a solid bronze, ball-bearing hinge butt is shown in Fig. 18. In this figure, the hardened-steel balls are shown at _a_, and the cones, which are also of hardened steel, at _b_. Bronze hinges constructed in this manner can be obtained at a slight additional cost above the ordinary steel-bushed hinge. Where hinge butts are exposed to the weather, as when used for exterior doors, bronze or brass butts should always be employed; and for extra-heavy doors that are in constant use, only the extra-heavy types should be used if permanency and durability are desired. There are a number of cheap grades of bronze, steel-bushed hinges on the market that are made of wrought or sheet metal. This kind of hinge has no merit, and should not be used on work of any quality.