Have you ever wondered why the phrase “the nuts and bolts of it” exists? The reasoning might help in remembering the biggest difference between screws and bolts. A bolt is defined as a threaded fastener with a nut and a flat bottom. It requires a nut to secure it to a material. The bolt can only be loosened when torque is applied to the nut. A screw, for all intents and purposes, is a threaded fastener without those attributes— it is defined as a screw head with a circular helical ridge. Screws are fastened by applying torque to the head.
Now that we have a firm grasp on the differences between a screw and bolt, let’s take a look at how the different variations of fasteners might be sorted. Screws can be subcategorized into more categories than bolts, these categories can be based on driving method, shape, and job requirement. Bolts are sorted into a more distinct category per unit, based on type and job requirement. The most common versions of each will help illustrate these sorting parameters.
The most prevalently used and recognized types of screws are slotted, Phillips, combination and Allen. Slotted screws are the most commonly used. They are denoted by a linear diagonal slot across the entire head. Phillips screws have a hole resembling an “x” shape and are associated with Phillips screwdrivers. Combination screws are a combo of slotted and Phillips, but the slot does not extend to the edges. Lastly, Allen screws have a hexagon shaped indentation, and are typically used with an Allen wrench or socket wrench.
Job requirements of screw variations vary. The most recognized of this category are wood screws and sheet metal screws. Both of these models have a name that gives away their purpose. Wood screws are made of wood and can be seen in an assortment of sizes. Spiral threads throughout the fastener are intended to provide a secure grip when penetrating wood material. On the other hand, sheet metal screws usually have a denser head and are used in conjoining sheet metal and various other materials. Their purpose necessitates threads on the entirety of the fastener.
As mentioned, bolts are sorted a bit differently than screws. Normally, these devices are categorized solely by their job requirement. Variations of this mechanism that are commonly seen are the carriage bolt, hex head bolt, and shoulder bolt. A carriage bolt is best for attaching metal to wood— it has a rounded top and a square bottom, to secure the fastener in place. Hex head bolts are, as the name suggests, six sided. These bolts are often used for installments of wood or metal. Lastly, a shoulder bolt is designed to connect components. This bolt is commonly used in moving parts, for example, pulley bearings and gears.
When assessing what types of bolt or screw you might need, remember to consider the following recommended specifications: required job type, shape, and driving method. These outlined parameters will provide a foundation in your quest for the most capable fastener.
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