What are the uses for different stainless steel bolts and fasteners?

Where would we have been without the huge range of fixings, bolts, screw and fasteners that we have today? It seem there are different products for just about every task you can imagine. How often, though, do you just grab the first one that comes to hand when doing a job on the car or around the home? Here is a guide to what you should be using.

The basic information

Stainless steel fastenings are highly useful and look superb but you should never use them in situations where they will be subjected to high loads and torque. They simply will not stand it and will fail, with all the catastrophic consequences that this entails. This warning is particularly important when dealing with the mechanical components on automobiles. Of late, there has been a surge in the "engine dressing" market where owners polish their motors to show standards and replace the nuts, screws and bolts with stainless versions. This is fine on unstressed parts but not on anything requiring torque application. An even more worrying development is the anodised alloy bolts that are being introduced as these are inherently extremely weak. The true value of stainless steel nuts and fixings is that they do not rust. This mean that they retain not only their looks but also their integrity in applications that are prone to water ingress.

What do the different fixings do?

Nuts and bolts Nuts and bolts are intended for use together. The bolt is passed through a hole or holes in pieces of work and the nut is threaded onto the end and torqued into place. Bolts differ from machine screws in that machine screw often seat in a threaded hole rather than requiring a nut to hold them in place.
Screws Screws are externally threaded fasteners that are designed to be used independently and are driven into close fitting holes in work pieces using friction to retain their position.
Hex cap bolts Hex cap bolts are similar in operation to regular bolts and require nuts to hold them in place. The difference is that the head of this type is held by an allen key as opposed to a spanner whilst being tightened. They are particularly useful in areas where access is restricted or space doesn't allow a spanner or socket to be used. Any of the above fixings can be raised head or countersunk. Raised head means that it will sit proud of the surface it fastens and countersunk requires a reciprocal hole in the work pice to allow the head to sit flush with the surface.