Fig. 334. - Lag and Coach Screws.
Fig. 335. - Button-Head Bolts.
Fig. 336. - Stove Bolts.
Iron. - Nearly all of the cheaper grades of butts, knobs, locks, etc., are made of cast iron. This material answers very well as far as the durability is concerned, the principal objection to it on this score being its liability to break under a blow or jar. For this reason it is not suitable for bolts, although it is often used for the casing of bolts. It is also not well suited for butts, as it often breaks from an unequal strain or sudden jar.
The cheapest method of finishing iron hardware is by coating with ordinary black varnish or with japan, the quality of the japanning or varnish depending upon the grade of the goods. Japanning is practically indestructible where the iron is not exposed to scratches or rubbing, and for durability is to be preferred to any of the lacquers or imitation bronzes.
"Berlin bronze," "Tucker bronze," the so-called "Boston finish" and nearly all lacquered hardware is finished by heating the iron and immersing it in a bath composed of linseed oil and gum-anime or copal, to which is added powdered alloys of copper and bronze, to give the desired color. When the coating thus obtained is dry the iron is roasted in a kiln, which seems to dry the preparation into the pores of the metal, and leaves it with a smooth, shining surface, imitating more or less closely dull bronze. Hardware treated in this way cannot be polished afterwards, all polishing being done to the metal before it is lacquered.