Getting the right o ring
Rubber o rings, for all their simplicity, are one of the finest examples of precision engineering and usefulness on the market.
They are cheap to make and buy. Proof of their practical value is that they are used in not only most machines, but in many different component parts.
Yet, despite their availability and cost effectiveness, it’s still worth knowing exactly which size o rings you need to buy to ensure you don’t get in a job lot of incorrect ones.
In the UK, o rings are measured on the BS scale (British Standard), ranging from BS001 to BS932. It is hugely important to get the right size when ordering as just a few millimetres out can deem them unusable or detrimentally affect the whole running of the machine they are fitted to.
As the BS numbers rise, the size of the o ring goes up too. To look in detail at the size, there are plenty of conversion charts which show the size measurements exactly. The format is written as ID x CS. The ID is the internal diameter, stretching across the length of the inside of the ring through the middle in one straight line. The CS is the Cross Section, or the thickness. This is measured by calculating the depth of the rubber at its thickest part (i.e. the centre of the torus). All measurements are in millimetres.
BS001, for example, is universally seen to measure 0.74 x 1.02. At the other end of the scale, BS932 would measure 59.36 x 3.00.
There are between these two numerous other variations, offering individuals the chance to order exactly the right size of o ring to ensure the product they end up fixed to works flawlessly. So, in just knowing the facts behind the jargon and abbreviations, you can be sure to order exactly the right size of o ring.