Faithful reader Cameron directed me to a quotation from an article on MLB.com by Anthony Castrovince (the MLB standing for Major League Baseball):
“Wakefield was a dependable eater of innings who annoyed opponents — not just on the days he pitched, but the day after, for a knuckleballer serves as quite the spanner in the works.”
(Translation, for non-American readers: Tim Wakefield is a pitcher who specializes in a rather unusual, fluttering pitch called the knuckleball. Wakefield himself, while he doesn’t produce spectacular results, has the ability to get his team fairly deep in the game without giving up too many runs: that is, “eat innings.” It is a general truth that, if a team faces a knuckleballer one day, its batters don’t do very well against a conventional pitcher the next day.)
I categorize spanner, meaning wrench (the tool) as a Doobious NOOB–that is, it is never found here–and spanner in the works as an outlier. The OED finds the first use of the latter in P.G. Wodehouse’s 1934 Right Ho, Jeeves: “He should have had sense enough to see that he was throwing a spanner into the works.”
I believe the expression will never achieve wide circulation here–will be used only, as Mr. Castrovince does, as a self-conscious exoticism–because we have a synonymous and, arguably, more adaptable and expressive counterpart: throw a monkey wrench in or into, which can be followed by works, plans, operation, or anything else. The OED reports a use of this by the Chicago Tribune back in 1907: “It should look to them as if he were throwing a monkeywrench into the only market by visiting that Cincinnati circus upon the devoted heads of Kentucky’s best customers.”
When Cameron brought up spanner in the works, it rang a vague bell, originating, I realized, in the title of a 1995 Rod Stewart album. I’d never known what this meant, and so categorized it with similarly mystifying British record names, like “Tea for the Tillerman,” “John Barleycorn Is Dead,” and “Thick as a Brick.” When I mentioned the expression to my wife, she reminded me that John Lennon’s 1965 book was titled A Spaniard in the Works. I had never before gotten the play on words. Good one, John.
notoneoffbritishisms.com 
🙂
For what it’s worth, “spanner wrench” (a redundancy?) did get some use here as a term for a specialized wrench that “spanned” a locking ring, of the sort that might be used to secure a lens into a telescope barrel. Such wrenches are often also used to remove the screw-on backs of wristwatches. The idea is that they have points that mate with holes or grooves in the thing to be moved and “span” the distance between them, unlike the usual sort of wrench, which grips the sides of the thing to be moved.
Perhaps some baseball writers will learn the useful phrase “wanking spanner” – that one should get out and about in North America more often.
“Wank” and “fap” are nonexistent in Canada. We have our own terms for that… And of course here it’s a wrench, not a spanner in the works.
I think this phrase comes from working-class sabotage. (‘Sabotage’ is from the French meaning throwing a shoe or sabot into a machine to stop it from working.) I think it’s a form of industrial protest – chucking a spanner in the works meant the cessation of labour while it was being repaired and a consequent loss to the owner of ‘t’mill’.
My father taught me the difference between spanners and wrenches when I was very young. Also that the inability to distinguish them is a sure sign of engineering incompetence.
A spanner is a precision tool that has flat jaws which engage the flat planes and angles of nuts and bolts. Some spanners (shifting spanners) have adjustable jaws. Ring spanners slide over the top of the nut or bolt and engage all sides. There are ring spanners for removing and replacing spark plugs.
A wrench is an adjustable tool with toothed jaws, used to grip things which do not have the flat faces of nuts and bolts. Pipe wrenches, for example, grip cylindrical pipes. Strap wrenches and chain wrenches do not have jaws, but are used to grip irregularly shaped objects.
A mechanic working on a machine such as a large printing press is more likely to be using spanners than wrenches. And dropping one into the works will lead to a large number of Very Colloquial Phrases being uttered.