Bolts are used with nuts and often with washers. The three basic types are carriage bolts, stove bolts, and machine bolts. Other types include the masonry bolt and anchor, toggle bolt, and expansion bolt, which are used to distribute weight when fastening something to a hollow wall. Machine bolts are manufactured in two gauges: fine-threaded and coarse. Carriage and stove bolts are coarse-threaded. Bolt size is measured by shank diameter and by threads per inch, expressed as diameter by threads (for example, 1/4 X 20). Carriage bolts are available up to 10 inches long, stove bolts up to 6 inches, and machine bolts up to 30 inches. Larger sizes usually must be special ordered.
Here are some of the more common bolts to keep in your toolbox:
- Carriage Bolts: Carriage bolts are used mainly in making furniture. They have a round head with a square collar and are tightened into place with a nut and wrench. The collar fits into a prebored hole or twists into the wood, preventing the bolt from turning as the nut is tightened. Carriage bolts are coarse-threaded and are available in diameters from 3⁄16 to 3/4 inch and lengths from 1/2 inch to 10 inches.
- Stove Bolts: Stove bolts aren't just for stoves; they are quite versatile and can be used for almost any fastening job. They are available in a wide range of sizes, have a slotted head -- flat, oval, or round, like screws -- and are driven with a screwdriver or tightened into place with a nut and wrench. Most stove bolts are completely threaded, but the larger ones may have a smooth shank near the bolt head. Stove bolts are coarse-threaded and are available in diameters from 5⁄32 to 1/2 inch and lengths from 3/8 inch to 6 inches.
- Machine Bolts: Machine bolts have either a square head or a hexagonal head. They are fastened with square nuts or hex nuts and are wrench-driven. Machine bolts are manufactured in very large sizes; the bolt diameter increases with length. They are either coarse-threaded or fine-threaded and are available in diameters from 1/4 inch to 2 inches and lengths from 1/4 inch to 30 inches.
- Masonry Bolts and Anchors: These work on the same principle as the lag bolt or screw; a plastic sleeve expands inside a predrilled hole as the bolt is tightened.
- Hollow Wall Bolts: Toggle bolts and expansion bolts are used for fastening lightweight objects, such as picture frames, to hollow walls. Toggle bolt wings are opened inside the wall by a spring. Expansion bolts are inserted into an expansion jacket, which expands as the bolt is tightened. The bolts are available in diameters from 1/8 to 1/2 inch and lengths up to 8 inches for walls as thick as 13/4 inches.