Factors to Consider in Finding the Right Screw
What's in a screw? You might just find the many details included in a screw's usual notation as a bit overwhelming. For instance, what does it mean to say a Steel Slotted Flat Head Wood Screw 1/3 - 18 x 8? Simply put, this translates to a steel material, flat head shape, wood screw type, which has a slotted drive style, and with 1/3 inch diameter, 18 threads per inch (TPI) thread count, and 8 inches length. In the end, knowing and understanding the critical attributes making up a handy tool part such as a screw could spell the difference between getting the right one that you exactly need and wasting money for a wrong part.
Drive or Slot Style
The name of a screw is frequently derived from the style of its drive or slot on its head. A Slotted head has a straight drive and is best for attaching basic joints like the face panel to a light switch outlet. The popular Phillips head bears a cross-like shape and commonly finds applications in hinges, appliances, and hardware. Meanwhile, the Multi-head, which includes the star-shaped Torx and six-sided Hex screws, is suitable for power drills or tools in machine and building industries and is also favored for consumer products to discourage disassembly.
Head Shape and Function
A screw may also be described by its head shape that usually goes well with its intended use. The Countersunk or Flat head is also referred to as the wood screw since its flat top permits it to be directed into tapered openings with its head deposited below wood surfaces typically found in furniture pieces. A sheet metal screw requires the Pan head, which carries the shape of a pan—a flat head that is matched with short vertical perimeter. There's also the Round head, which resembles a semi-circle surface and is ordinarily called the machine screw for its ideal usage with cars or hard equipment.
Critical screw dimensions include the diameter and length, which are both measured in inches, and the thread count, which refers to the number of threads per inch (TPI) found within the screw's length.
For small screws, a number usually denotes diameter size, with the hash tag “#” sign preceding the number. Otherwise, the major or thread diameter serves as the most relevant size for the width of a screw. Length measurement for a flat head is taken from the head that levels with the surface until its end. For pan head types or screws with inverted head, length measurements starts from the head part attached to the body of the screw.
The most popular material used for screws is steel, which may come plain or combined with surface treatments like galvanization, chrome, and zinc plating. Compared to regular steel, stainless steel has a more anti-corrosive, inherent property. Similar to stainless steel, aluminum alloys is inherently anti-corrosive and is usually used for rivets. Aside from being intensively resistant to corrosion, brass is also electrically conductive but remains relatively soft. Bronze boasts of superb anti-corrosive property and greater strength, thereby demanding high cost.