Screws are fasteners which are used to hold to objects or materials together and are integral parts of wooden items, machines, buildings, electrical appliances, etc. A screw is made of metal which is usually stainless or galvanised steel. The top part of the screw which is visible even after it is embedded into the material is called the head. The end point of the screw is sharp to drill inside the material. The cylindrical body of the screw is called shaft and is characterised by threading in a helical pattern. Best best quality screws online (cap screw, drywall screws, pan head screw, csk screw, lag screw, bolt screw, brass screws, black screws, stainless steel screws) with best offers. The portion just below the head is called shank which is smooth in some types of screws.
The screws can be classified on the basis of some factors. They have been discussed here.
Materials Involved
The screws can be classified on the basis of materials for which they are required.
- Wood Screw- Wood screws are used to attach sections of timber with one another. The wood screws have partially unthreaded shanks and differ in terms of threads per inch of length. Wood screws with low number of threads per inch length are suitable for soft woods such as spruce or pine. For hard wood species, screws with fine threading are suitable. The head of a wooden screw can be round or flat. It can be made of brass, stainless steel or plain steel.
- Machine Screw- Machine screws are a cross between bolt and screw. The function of machine screws is to fasten metal to metal or metal to plastic. They are commonly used to fasten electrical components such as light fixtures with electrical points.
- Drywall Screw- Drywall screws are used to attach drywall with timber or metal studs without causing damage to the drywall. The drywall screws have bulge heads which are self-tapping. The screws can also be coated with black phosphate.
- Decking Screw- Decking screw is also called lag screw. They are longer in length and have large diameters. Such screws are used to attach deck boards and are also commonly used in docks and wood-retaining walls. The screws are resistant against corrosion because the exterior wood tend to be corrosive. Lag screws are heavy duty screws and are also known as coach screws.
Head of The Screw
The screws can be divided into countersunk screw and non-countersunk screw on the basis of the design of the screw heads. In a countersink screw, there is an angular shape beneath screw head which requires you to drill a hole with the correct head angle so that the screw is housed perfectly. In a non-countersink screw, the head does not have an angle and the screw head is present outside the surface. Hence, there is no need to make a pre-drill hole to house the screw head.
Countersink screw head- The following types of screw heads are countersink screw heads.
- Flat screw head is entirely flush with the surface. The top surface of the screw is flat but is cone shaped underneath the surface. The angle from the top surface of the head to the part where the head meets the threaded part is called the degree of a flat head. The standard degree of flat head is 82 degrees although flat screw heads with 90 degrees and 100 degrees angle are also available.
- Raised screw head or oval screw head is same as a flat screw head. The only difference is that the head is dome shaped and sticks out of the surface.
- Bugle head screw has a flat top surface but the portion underneath the top surface has a concave shape. The concave shape allows distribution of stress over a wider area and reduces damage to the surface. Bugle head screws are self drilling screws which means there is no need to drill pilot holes to install them.
Non-countersink screw head- These are the various types of non-countersink screw heads.
- Pan head screws have flat or slightly round heads with sloping edges. The surface underneath the head of a pan head screw is flat.
- Truss head screw has a domed head and flat surface. The flat load bearing surface has extra width which makes the screw stronger. The screw head sticks out from the surface which makes it ideal for decorative items such as ottomans.
- Flange screw has a circular or hexagonal head with a circular flange underneath the head. The circular flange helps the screw in retaining its position and distributes pressure which increases the load bearing capacity of the screw. Flange head screws are self tapping screws.
- Socket head screw is a variant of cap screw. A socket head cap screw has a cylindrical head with hexagonal drive. The sides of the screw are long and vertical. This is a heavy-duty screw made of stainless steel and high-grade carbon and is used in automobiles and construction industry.
Screw Drive
Screw drive is the design of a screw which allows it to be turned and installed using a screwdriver or Allen wrench. The screw drive determines the manner in which the screw attaches with the surface.
- Slotted- Screw with slotted drive has a single slot on the head and needs a flat bladed screw driver.
- Hex Drive- Hex drive screw has a six point slot in the head which needs a wrench or socket with 6-12 points.
- Hex Socket Drive- Hex socket drive screw has a rounded head having hexagonal slot. It is also called allen screw because it needs a hexagonal wrench called allen wrench.
- Philips- Philips screw has a cross slot on the head which helps it in staying at the centre during drilling. Philips screw is a self screw.
Special Types of Screws
Grub screw which is also known as set screw does not have a head and is fully threaded. Even if a grub screw has a head, it will be fully threaded with no smooth shank between the head and the shaft.
Ball screw functions by converting rotational motion to linear motion. A ball screw has a ball nut and a threaded shaft. Ball bearings are present between the nut and the shaft which provides a rolling motion to the nut over the threaded shaft.
Lead screw also converts rotational motion to linear motion. However, a lead screw is different from ball screw due to the fact that the nut slides over the threaded shaft instead of rolling.
Purchasing Screws
When you need to buy screw, you must ensure that the screws you purchase must match the project. For simple projects which do not require drills, screws with simple heads and simple drives such as Philips are suitable. For heavy-duty materials, screw heads with multiple grooves and points are suitable. You can access all types of screw online due to presence of many online stores.
The screw price depends upon its design, material, size, screw head and brand. Prices of specialty screws will be more as compared to conventional screws. For example, ball screw price is more as compared to a simple screw. The type of head is also an important determinant of the screw. For example, star screw price is more as compared to a slotted or Phillips screw.
Machine screws are heavy duty screws. Thus, the screw machine price is more as compared to wood screw price. But the price of a machine screw is lesser as compared to self drilling screw price. This is because self drilling screw has a drill shaped point which can cut through metal and does not require a pilot hole.
Material of the screw is also an important factor. For example, steel screw price is more as compared to aluminium screw price because steel is a heavy duty metal.
You can compare the screw price list for various types of screws on different online stores to get the best price.
Screws Price List
