The difference according to a thesaurus is that there is no difference as bolts and screws are regarded as synonyms of each other. Whilst it would be easy to lump all these fixings together (it would make our job easier!) there are actually significant differences which a user needs to be aware of before making a purchase.
It is true that, to the naked eye, there does not appear to be much difference between a bolt and a screw. They are both threaded fixings and have a head for tightening the fastener but there is more to it than that.
The most obvious way of differentiating between a bolt and a screw is that a bolt is not usually threaded all the way along its shank as it has a plain portion. A screw, however, is threaded fully to the head.
A screw is usually installed into a tapped hole, unless it is a self-tapping screw which creates its own thread. Screws don’t need nuts, as they become secure by being tightened into the hole with a screwdriver or driver bit which fits into the drive recess. Generally speaking, screws are shorter than the width of the material they are being screwed into, so that they don’t protrude on to the other side.
Bolts are designed to be installed with a suitable nut. The hole for a bolt is not tapped as the bolt is pushed through and is fixed and tightened using a nut at the back of the material being fastened. So a bolt will be longer than the width of the material it is being used on, as it needs to protrude through to the other side to screw into the nut.
The unthreaded portion of the bolt (which sits inside the material) adds strength, making it more resistant to shear forces, compared to fully threaded screws. Bolts are usually fastened using a spanner or other tool which grips the head whilst the nut is tightened.
Bolts can also be used in the same way as screws though, if they are installed into threaded components.Fully threaded bolts (also known as set screws) are also available.
Bolts and screws for security applications:
The development of bolts and screws, particularly where security is a factor, has been driven mainly by the applications they are being used for and the level of security required. For example if the fixing is permanent and not requiring removal, then a shear bolt (which has a snap off head leaving a plain head with no drive to remove the bolt) might be suitable.
For a removable fixing, the head is the important factor as the drive used to fix and remove it should not be generally available. Security driver bits are available, which may be specifically matched to the head of the security screw, to prevent unauthorized tampering.
Arel Fasteners supplies a wide range of general fixings and security fasteners for all applications. As you browse the ranges you will see the extent of the choice available, so if you are unsure of which fastener will be most suitable for your application, please call us – our sales team are always on hand to assist with your queries.