Filing is fun

I once asked a mate why he hadn’t stuck with bicycle frame building when he tried it out prior to the start of a long and more-or-less successful career in cycling journalism. ‘Filing’, he said; ‘I couldn’t stand spending ages filing tubes.’

Maybe it’s as well he found out sooner rather than later that not every facet of frame building is glamorous, for most of them aren’t. For every minute spend playing a carefully-adjusted oxy-fuel flame over tubes and lugs fluxed and ready for the brazing rod, hours must be invested in the more mundane processes of measuring, marking out, rubbing down and, yes, filing.

And yet filing is, alongside brazing and silver brazing, one of the cornerstones of the frame builder’s craft. It is not easy to do well and, if done badly, lets the whole frame down, whether visible or not. Using a file properly is about more than simply removing metal with a few well- (or ill-) chosen strokes. The great Henry Royce was reputed to be able to file a perfect hexagon freehand and, while this degree of toolmaker’s virtuosity may not be required when building bicycle frames, it is indicative of the results that may be obtained when using what looks like a simple tool.

Getting good results needs, not surprisingly, correct technique (get instruction if you wish to master it) and sharp tools. Hand files are made in a wide variety of shapes, from the good old flat file to the frame builder’s friend, the half-round. They also come in various lengths and in degrees of coarseness: bastard, second and smooth cuts being the most commonly found. Coarseness is relative to the length of the blade, so that a smooth cut six inch is finer than a smooth cut 10 inch. My personal favourite for shaping mitres is an eight inch half-round second cut…

A file previously used on aluminium is next to useless on steel and files for use on steel and stainless steel should be kept separate. In fact, it is no bad idea to have a vast selection of files, each suited to some specific task, and to have them mounted on a wall board for easy access. Happily, this allows owning and working with hand files to satisfy the most demanding of OCD urges.

What, then, is frame building’s most enjoyable filing exercise? Some builders will doubtless enjoy carving the intricacies of baroque lug work, while others might find joy in shaping a perfect shoreline (the edge of a lug) or crafting a perfect transition from rear stay or fork blade to dropout, but nothing, surely, beats the satisfaction to be had from filing the perfect tube mitre. It’s a job often done by clamping the tube to a lathe or mill and passing it over a tube cutter of the required diameter set at the precise angle. This is a great way to save labour where numerous tubes must be cut to the same angle, but not necessarily in small-scale manufacture as a competent worker can mitre a tube by hand in the time it takes to clamp the work in the machine. It’s possible to achieve as close a fit by hand as by machine – and a lot more satisfying. 

If there’s a downside to this rewarding activity, it is surely the process of ‘cleaning up’ excess brass or, worse because a lot more expensive, silver solder left, perhaps, around the shoreline of a lug or in a blob clinging to the side of a tube. Removing the excess is time-consuming and doing it without damaging the thin sidewall of the tube a task that requires a rock-steady hand, which is where neat brazing technique comes in handy…

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Winner: Bespoked 2015 Best Touring Bicycle