This is my Campy Peanut Butter Wrench. It was given to me by an older bike mechanic at a going away dinner before Ms. Fishy and I moved to Australia.
The Peanut Butter Wrench is something of an icon in bike tools and it was presented to me as a bit of ceremony welcoming me into the world of bicycle mechanics. I’d worked with him in a not-for-profit bike shop, helping people fix their own bikes and repairing bikes as an act of charity. He’s a bit older than me and had been doing it far longer, so there was a rather paternal air to the whole thing.
But that’s not what this tool means to me. I do like the sense of history and connection that it represents, and it was intended to represent that. But it also is a reminder to me to stay true to my rational, evidence based beliefs.
You see, at the time of that dinner I had recently returned from attending two weeks of profession mechanic’s training at Barnett’s Bicycle Institute. I chose that facility because they emphasis testability and repeatability in their procedures.
The primary example of that is their insistence on using torque wrenches wherever possible to tighten threaded fittings. This is an unambiguous way to tell if such a fastener is done up correctly. There’s a notion amongst folks that don’t do such jobs regularly that the tighter the better, but It’s more complicated than that.
Obviously not tightening something enough is a bad thing. But so too is over-tightening. Put too much stress on a fitting and it can fail abruptly when the load causes the nut or bolt to crack. There’s an acceptable range of force for all these things and a torque wrench allows you to know if you’re inside that range.
When I first started using torque wrenches I was shocked to find that how tight things felt was very different at different times. In the morning I’d do up a wheel nut, a job I’d done thousands of times, and I’d look down at the torque wrench and think “Is this thing right, that felt too easy.” and at the end of the same day I’d do the same job and look at the thing and think “Is this thing right, that was too hard.”
How things feel is a product of the effort required by the parts and how you feel at the time. Too much coffee, a bad nights sleep, a difficult interaction with a customer can all affect how you feel, which affects how difficult it feels to tighten things.
So what’s this got to do with the Peanut Butter Wrench?
The mechanic who gave it to me also gave me some advice. He told me to stop using torque wrenches because “You know how tight something has to be.” and because he’d seen them go out of calibration.
No, no I didn’t. I do now to a certain degree because of all the years I’ve been using a device that objectively tells me how tight I’m making threaded fittings. But the variability of my subjective sense of “tight” is unchanged so I will always use torque wrenches. Mind you, his warning about calibration was a good one. I get my wrench professionally calibrated once a year.
I value truth. I value evidence. And I value my customers enough to want to get it right every time. Tradition and history be damned.
To never compromise on the need for demonstrably objective standards is what that Peanut Butter wrench means to me.