All about screws and bolts
Screws and bolt belong to a group of threaded fasteners. The threads can run right handed or left, tapered, straight, or parallel. There are basically two kinds of screws, machine and wood screws. The two are manufactured from metal; although the machine screw carries steady diameter and combines with nuts while the wood screw is tapered and grabs the actual wood surface.
Screws are usually made out of low to medium carbon steel wire, but hard and low-priced metals might be substituted, like brass, stainless steel, aluminum alloy or nickel alloys. Quality of the metal being used is of great importance so as to eliminate cracking. When a finish is applied to the screw, it is usually well-matched. Steel might be coated or plated with zinc, cadmium, nickel, or chromium for added protection Fastener material can be vital when selecting a fastener because of variations between materials in strength, corrosion resistance, brittleness, galvanic corrosion properties and obviously, cost.
When changing fasteners, it is usually advisable to match up what you really are changing. Substituting one bolt with a stronger one is generally not safe. Harder bolts are usually more brittle and may not work in certain applications. Additionally certain equipment has safety checks designed to ensure that specific bolts will fail before more expensive or important items are destroyed. Another example of application specific fasteners can be seen within a salt water environment, where galvanic corrosion needs to be considered when replacing fastener materials.
Steel is considered the most familiar fastener material. Steel fasteners are found plain or coupled with a variety of surface treatments like zinc plating, galvanization, and chrome plating.
Steel fasteners usually are available in 4 grades: Grade 2, Grade 5, Grade 8, and Alloy Steel. Various other grades exist also. Grade 2, 5, and 8 are often plated with a moderately blueish or yellowish zinc coating, or are galvanized, to withstand corrosion.
Stainless steel is an alloy of low carbon metal and chromium for improved anti-corrosion functions. Stainless steel is greatly corrosion resistant due to the fact that the anti-corrosive properties are built-in to the metal, it will certainly not lose this resistance in cases where it is scratched in the course of installation or use.
It is a popular error that stainless steel is tougher than normal steel. In reality, because of their low carbon material, a lot of stainless steel alloys cannot be hardened by means of heat treatment. Hence, in comparison with regular steel, the stainless alloys used in bolts are somewhat tougher when compared to an un-hardened (grade 2) steel but substantially weaker than hardened steel fasteners. Only if great care is taken, stainless fasteners are prone to seizing up at the time of installation, a trend known as galling.
Most stainless steel fasteners are noticeably less magnetic when compared to normal steel fasteners even though some grades will be slightly magnetic.
Brass is an alloy of mainly copper and zinc. Brass is really corrosion resistant and electrically conductive. Although, its use as a fastener is quite limited on account of its relative softness it is used mainly for its physical appearance
Aluminum is mild, soft, corrosion resistant steel. Similar to stainless steel, aluminum's corrosion resistance is built-in to the material. Consequently, scratches and nicks will not likely affect the corrosion resistance.
Fasteners are manufactured from many different aluminum alloys, with components such as manganese, silicon, iron, magnesium, zinc, copper, and silicon being included to increase toughness and melting point.
Rivets are usually made out of aluminum alloys in the 5000-series, which utilizes magnesium as the main alloying component.
Many steel fasteners are electroplated with zinc to improved rust resistance. Fasteners which are zinc plated have a glossy, silvery or even golden looks, known as clear or yellow zinc respectively. They are definitely corrosion resistant and will eventually corrode if the coating is wiped out or if exposed to a marine environment.
Hot Dip Galvanizing
Galvanizing is yet another coating which involve applying a layer of zinc. Hot dip galvanizing places the thickest coating on the metal, causing superior corrosion resistance. Because of the thickness of the coating, hot dipped galvanized bolts are not appropriate for other nuts. Galvanized nuts are tapped fairly more than other nuts to fit this coating. Hot dipped galvanized fasteners are often used outdoors, particularly in coastal environments.
Fasteners are chrome plated and polished for visual appeal. Chrome plating offers same corrosion resistance to zinc plating. The major issue with polished chrome is its high price. If more corrosion resistance is needed, stainless steel may be chrome plated; stopping any corrosion should the chrome be penetrated.
Here at Metro Bolt located near Detroit Michigan you can buy fasteners online. Metro Bolt has the nation’s largest selection of fasteners along with other construction supplies to satisfy your jobs needs.