Let's Torque about it

OK, let's start with a quick bit of word association.

If I say "IKEA", what do you think of first?

• Self-assembly furniture.
• The letter Ø or Ö.
• Vikings.
• Meatballs.
• Queueing.
• Mitch Benn's fantastic song.
• The futility of life on Earth.

Personally, I think of these:

Aside from their furniture assembly uses, I was surprised to find that the Allen key is also a staple of bicycle building. In actual fact, some of the keys I used in assembling my bike were actually ones left over from furniture I've assembled in the past. They do the job perfectly.

Most of the time, anyway.

For tasks which aren't part of the standard cable-loosening-or-tightening maintenance routine, you sometimes have to take more care. Attaching your handlebars to the stem, for example - another occasion where I read my least favourite of all phrases, "catastrophic failure", a few times.

This was with reference to the over-tightening of the bolts on the clamp which grips the handlebars firmly in the stem:

As you can see from the picture, there are four of these on my stem, and from the manufacturer's instructions (Cinelli in this case), it arises that it's important these are tightened equally and, most importantly, not over-tightened, lest the bar become over-stressed and break. The equal tightening bit is easy, just give each bolt a turn or two, then move on to the next one, turn it the same number of times, wash, rinse, repeat. Simple.

But what about not over-tightening them? Other than just guessing based on how tight the bolt "feels" when you turn it (which on my scale ranges from "single finger whee" through "twiddle" to "whole body nggggghhhh"), how do you actually adhere to the manufacturer's tightening instructions?

The answer is with a torque wrench, my new favourite piece of kit:

It consists of a long "body" (the handle end is the black rubber bit), and a number of Allen key heads of different sizes. Simplistically, just attach the right size of key to the body, and it works just like a standard Allen key, but crucially prevents you from over-tightening bolts.

Through some combination of magic and engineering, you can twist the handle of the body to set a "maximum torque" (measured in Newton metres, abbreviated to Nm). Manufacturers are usually kind enough to mark on the things to be bolted together the maximum torque which should be used. Alternatively, you'll find it in the manual that came with the parts in question.

When you're tightening the relevant bolts, the wrench will make a little "click" sound to indicate that you've reached the tightening limit. It really is that simple.

The thing about torque wrenches, though, is that they're precision equipment (mine came with a calibration certificate and everything), and consequently not cheap. Mine cost me £48, and so far I've used it to tighten a grand total of 4 bolts - £12 per bolt, if you look at it that way. But hopefully my handlebars won't fall off, and I value that as worth much, much more.