A rigger from a large rigging equipment user recently asked for my opinion on a sample from a batch of collared eyebolts, roughly equivalent to shoulder eyebolts in the USA, that it had purchased. The supplier had, at its request, stamped on individual identification numbers. Fine in principle, until he showed me where they had been stamped: the machined surface on the underside of the collar.

It is easy to see why this might have seemed like a good idea to the supplier. It was a nice clean flat surface and the eyebolt could be clamped easily into a vice while the stamping was done. Furthermore, the size of the characters was quite large, too big in fact for the raised flat areas provided on the forged eye for marking purposes. Perhaps the supplier didn’t have the right size stamps. However, hard stamping inevitably displaces the material and raises a ridge to the side. Collared eyebolts rely on proper seating of the machined collar onto a machined boss to resist angular loading. Anything which compromises this is not a good idea.

Whilst this is the first time I have come across stamping in this particular position, regrettably it is only the latest in a long line of poorly stamped markings I have seen on eyebolts and many other items. Forged items such as eyebolts and shackles usually need several markings and it can be a problem to accommodate them all if insufficient thought is given. There is the working load, the thread size, the material grade, the manufacturer’s identification, a batch identification and, certainly within the EU, the CE marking. All of these can be raised in the die or embossed during forging. Indeed the equipment standards usually specify where they should be marked and make provision for additional stamping such as the raised flats on eyebolts. Often they are the only markings on the item unless the buyer specifies otherwise, which is where individual identification marking comes in.

Why is an individual ID needed? Batch numbering is not a problem for new supply, but spare a thought for the person who will be expected to thoroughly examine the item at regular intervals throughout its life. Would you record as safe to use an item that carried only a batch number identical to several thousand others in circulation? I certainly wouldn’t. Hard stamping individual IDs takes time and therefore costs money but it is far easier and cheaper to do en masse in the workshop before delivery than out in the field during an examination. And by keeping the number of characters to a minimum, the additional effort required of the supplier is also minimised.

Hard stamping indents and displaces the material. If the indent is too sharp or too deep it will be a stress raiser and lead to cracking. The marking should therefore be on a low stress area of the item and the size of the characters kept to a minimum consistent with legibility. Bear in mind that standard stamps are for flat surfaces, so if stamping on a curved section, the centre will have to be a different height than the edges to get a complete character. The bigger the stamps relative to the curve, the worse this problem gets. I once saw some shackle bodies where the stamps used were so big that the characters had been turned through 90° and the ID stamped vertically. The indents were so deep that, had they been notches arising from damage in service, the user would have scrapped them.

Individual ID marks are essential, but I still occasionally see additional unnecessary marks stamped into equipment. The date of the next examination used to be a favourite. Inevitably it has to be hammered over to obliterate it before the next date is stamped, causing unnecessary and hidden damage to the item. Plant numbers which often change are another example. In most cases there are other ways of conveying this information, such as colour coding or the use of tags or marking plates, depending upon the equipment in question.

The quality of stamped markings sometimes also leaves a lot to be desired. The whole point of them is to communicate essential information to the user. Incomplete characters arising from worn or wrong size stamps, over-stamping and careless spacing all lead to lack of clarity.

Finally, there is the matter of the information itself.

A couple of years ago a young colleague, metric from birth, finally discovered what a hundredweight was, and that its abbreviation was CWT. He admitted to having wondered what a “cuwut” was. Indeed there are probably a lot of other young people out there who are similarly confused, as I still see new equipment on sale with working loads marked in imperial units. Given that the UK standards went metric decades ago, this is hardly conducive to clear communication.