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I purchased Pinhead security skewers, and the instructions suggest to tighten them to 8 N-m (70 in-lb) of torque. However, the skewers use a special key which doesn't appear compatible with a torque wrench, so how can I figure out how much torque I am putting on them?

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Put your torque wrench on something else to get a feel for how much force you need to apply to the tool you have, then do your best. My cynical take is that anyone who can't make their gizmo compatible with a torque wrench has no right to expect accurate torque.

Looking at their website the key does seem to have a square-drive option if you take it apart. I screen-shotted their zoomed view to get this:

enter image description here closeup of pin-head key

If you're lucky that axle will be removable, either because it's got an allen head and can be unscrewed, or it pushes out. It might be a destructive removal so maybe do that to a spare key.

Once you have the square-ish head exposed I expect you'll be able to find a socket that fits it for your torque wrench. Those 12-slot sockets are designed to take square or hex bolt heads, and this is one of the few times with a modern bolt that you'll actually use that feature :)

I'd be doing that anyway because that key is just obnoxiously large to carry everywhere (which you have to do if you want to be able to put on a new tube).

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    For comparison, BTW, pitlock "keys" are a 14mm nut with a 6mm hole through it so you can use a spanner or the shaft of a 6mm allen key... like the one on the multitool you already carry. Or what I did is buy a 40mm diameter keyring to carry it on, as that provides enough leverage to get most of my QRs undone. – Móż Oct 26 '15 at 1:40
  • I've got both models of pinhead on my bikes. The key type you picture above for QR wheels doesn't have a square drive. There's a rectangular part with a round hole. You could drive the pin out but you'd only be able to get an open ended spanner on it. The version for nutted axles is a hex, 14 or 15 mm I think as well as being cross drilled for a T-bar like the pitlock. I've once had trouble with the front QR working loose after taking the wheel off, in about 5 years. – Chris H Oct 26 '15 at 7:54
  • The keyring part is slightly smaller than the keyring bike tool I used to keep my garage keys on, it's not actually too bad. Mine stays in my pocket all day. – Chris H Oct 26 '15 at 7:59
  • @ChrisH I'm surprised that you couldn't get a socket onto the square end. But ok, you'd have to use a shifter. Did you happen to notice if it's a nice metric size? – Móż Oct 26 '15 at 8:01
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    It's no bother -- or it wouldn't be if the Verniers hadn't been "borrowed" from my desk. A ruler says 8.5x12mm though. – Chris H Oct 26 '15 at 13:06
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I only recently bought a torque wrench small enough for bike use. You can get quite a good idea of the torque by working through the physics to find what mass you'd be lifting given the leverage of the tool, then applying a similar force to lifting such a mass (ideally something you'd hold in a similar way). For pinhead skewers this works out to being quite firm with it but not using maximum effort. For me.

Torque measurements don't say very much about the actual tension force in the skewer anyway, because the relationship between the two depends on the friction between the nut and the skewer,as well as between the nut and the drop-out.

I could be wrong but I've a feeling they sell a socket type adaptor for the skewer type kit as well as the keyring.

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