There’s no single, universal steel. The fact that steel is an alloy, a mix of different elemental minerals, practically guarantees that there is more than one way to make the stuff. As a result we have steel in a variety of compositions, each of which can withstand a certain amount of abuse and perform well under specific conditions. We assign grades to steel to make these differences clearer. Generally, the more carbon a steel fastener contains, the more it can be hardened, and the addition of other metals may provide other desirable qualities as well.
When looking for ways to reduce waste, cost-conscious and environmentally aware manufacturers and consumers may consider reusing metric bolts and screws. But not all bolts and screws can be safely and effectively reinstalled after being removed from an assembly or component. In fact, an unequivocal “yes” is never the answer to the question of whether a fastener can be reused. Depending on the situation, the answer is always either “no” or “it depends.”
High-strength bolts that have been pre-tensioned into their proof load range – the point at which they permanently deform and do not “snap back” when relieved from their loads – should not be reused. This is the case in many applications, as structural and other bolts used in the manufacturing, construction, and automotive industries are commonly tightened to a torque value that creates a sufficient clamp force to prevent joint failure.
Like most aspects of construction and manufacturing, choosing the proper tool for the job goes a long way toward determining the project’s success. Selecting a metric fastener’s drive recess (the slot or hole into which the driving tool is inserted) is no different. Drive recesses, from Phillips head screws to more unusual shapes and specialized uses all have advantages and disadvantages. Take a look at some of the drive types Mr. Metric offers to learn about which style is right for your job.
Ensure Proper Tightening & Removal of Metric Fasteners With the Right Drive Type
Slotted – The first and still one of the most common varieties, slotted metric screws are inexpensive and come in virtually any head shape desired. They are also the easiest to torque when using a screwdriver to remove corroded or frozen fasteners, so they are often used when field installation and/or removal is necessary. However, they are unsuited for automated driving because the single slot allows the bit too much tolerance, and slippage and off-center engagement can occur. (more…)