Who invented the Allen key?

Q: I WOULD like to know if there is an ‘Allen’ who invented the Allen key because if there is I reckon he must be a very rich man. Or she must be a very rich woman. I have looked this up on the internet but there is a lot of conflicting information – can you find an expert to answer this?

Our expert is John Bates from the The Traditional Tools Group (TTTG), an organisation dedicated to the study, conservation, collection and use of tools of all kinds.

A: An Allen wrench, Allen key, hex key or hex head wrench is a tool used to drive a particular type of screw or bolt known as a ‘socket head cap screw’ which has a recessed hexagonal head. In many non-English speaking countries it is known as an ‘Unbrako key’ (also often misspelled ‘Umbrako’ viz IKEA).

The Unbrako is in fact a brand of socket head cap screw established around 1911 by the SPS Company of USA. This company is also said to have actually invented the socket head cap screw. However, while this claim is certainly possible it can’t be readily confirmed.

In order to determine the origin of the Unbrako or Allen key we need to look at the history of the screws they were designed to drive.

What we do know is that the SPS Company was a very early manufacturer of the socket head cap screw. It also became a world leader in mass-producing it (it was branded ‘Unbrako’ because it is supposedly unbreakable – which in absolute terms it isn’t).

The reason it is known by different names in different markets is probably due to the SPS Company’s decision to produce metric sizes for the European market in the 1950s.

The Unbrako brand is now over 90 years old and, in terms of product quality, remains the socket screw by which all others are measured. From its release it became the socket screw of choice for engineers in the US and Britain. In the decade before and after World War II, the product spread to all worldwide markets and today is recognised as the brand and performance leader in over 25 industrialised countries.

Despite this brand dominance, the term ‘Allen key’ is still part of the mechanical engineer’s lexicon, originating from the products made by the Allen Manufacturing Company of Hartford, Connecticut, USA. That company was also a maker of socket head cap screws featuring the recessed hexagonal head. Consequently, the ‘Allen screw’ is another commonly used name for socket head cap screw.

It is widely reported that in 1943 the Allen Manufacturing Company trademarked the name ‘Allen wrench or key’ for its range of hex wrenches. The Allen Manufacturing Company is no more, but the brand is now owned by the Danaher Group in the USA and used by its industrial tools division which still produces the ‘Allen’ wrench or key.

While the socket cap screw has been around for much longer than, and has been produced by, many, many companies, the popularity and wide market distribution of the Allen Manufacturing Company’s ‘Allen Key’® has continued to exert an influence on terminology.

I am aware that the prefix ‘Allen’ has been commonly used in reference to both the wrench/key and the fastener/bolt in both Australia and the USA for many decades – see www.nickel-systems.com.

In summary then, the ‘Allen’ wrench or key has been in existence for as long as the socket cap screw it is used on, so it was definitely not ‘invented’ by anyone connected to the Allen Manufacturing Company. As to the person after whom the Allen Manufacturing Company was named, well that’s another story.

Speaking of which, an interesting tale behind the Allen wrench/key question concerns the issue of who did not invent it. Several imaginative but unsupported stories and theories appear on various web pages.

One of the more common is an erroneous account that the inventor of the Allen wrench was one Gilbert F. Hublein (1850-1937), a German immigrant who happened to be a liquor importer in Hartford, Connecticut (see www.cosci.org).

Where to find out more

Visit The Traditional Tools Group for more insights into the history and use of tools of all types, a comprehensive listing of other interested groups and associations, information about vintage tools and fascinating links

For more about the SPS company visit the SPS company history page