There are a few tools that any worthwhile home toolkit should contain, and a good cable cutter is high on the list. Sure, you can try and get by with some cheap side cutters or the vaguely sharp bit in the jaws of a pair of pliers, but once you’ve chewed your way through a gear cable with an inadequate tool the chances are that the end’ll be so thoroughly mangled that it won’t go through the housing. And the chances of you being able to cut the housing cleanly is pretty much nil anyway.
A proper cable cutter, like the Park one pictured, makes cable replacement a breeze. It’ll snip its way through gear and brake cables and housing with ease, leaving lovely clean ends for free-running action. Most also have crimping jaws for squeezing end caps on to the cables for a neat finish. And if you ever need to dismantle a wheel with chronically siezed or split nipples, then your trusty cable cutter can even despatch most spokes…
As with all tools, it’s worth getting the best you can afford – the popular Park and Shimano items are about thirty quid, but they’ll last for years.