Camilo

Actually, I still disagree that a 1/4 to 3/8 (or similar) adapter would in any meaningful way affect torque. It has virtually no additional length compared to a socket or a hex key and therefore as little or no comparison to the type of torque loss the guy above was describing. He was talking about extensions with significant length. I really don't believe for a minute that a socket adapter, with it's 1-2 cm of length, would affect torque, and this is even more so at the low torques for most bicycle applications - just not enough force to twist and deform a 1-2 cm. adapter. You may be technically correct, but not in any meaningful, or dare I say measurable? way.

Grand Bois

No and yes.

San Rensho 

Great site, thanks. I came across this calculation when working on my Ducati. To torque the head bolts you need to use a crows foot (actually a $pecial Ducati tool, but crows foot works). The manual said that as long as the crows foot was perpendicualr to the torque wrench, the torque reading on the wrench was correct.

Its completely counterintuitive that if the foot extends forward on the torque wrench, the applied torque is less than what the wrench reads and vice versa if the foot extends backwards.

kenhill3

Anything (ie. crow's foot) that effectively increases the moment arm of the force/leverage applied to a fastener by a torque wrench in fact applies more force than the reading on the wrench. This is an absolute fact.

About the adapter or extension thing though- you all have got me thinking about this and I definitely have no answer to this as yet. Take for instance an extension that is, say, 20 feet long (extreme illustrative example). At least at higher torques that extension will twist along it's length, which I guess you would call torsion. The question I would have is this- is the force at the end of that extension equal to that which is originated at the wrench end? I don't think anyone has, as yet, examined/explained this here, at least not for me. Even if this torsion does indeed effect the force value, I surmise that using an adapter or short extension has negligible/inconsequential results.

But hey, whadda I know? I'm just a dumb carpenter.

Upassdme

You're right. I wasn't saying that anyone should actually calculate in torque loss on anything. The amount lost through 1-3 inches of extension is negligible and even in the most cheaply made tool available you wouldn't notice it. The link I posted was just the answer to "how to calculate torque lost", which prompted some nice pictures and things of the like. The ranges that are set into any specification are sufficient to allow for loss, wear, and other things that can cause over or undertorquing. I also can't really see an area of a bike that you would need more than 3 inches of extension to repair, replace or adjust anything. Realistically, I'd also never use a crow's foot on a bike either, I think it might cause more frustration than it would be worth.

In a nutshell - beam type torque wrench is fine, the craftsman will work great for a long time unless you're doing something professionally where durability is an issue, then I'd go Snap On there really is no substitute. Beams are also more accurate, little harder to read. There is torque loss through an extension, though with a torque range and really short extensions I can't imagine why you'd worry. I put the link up for people that wanted to know not to start an arguement, personally I find physical properties of things pretty fascinating, I'm a minority in that respect but I'm not alone.

Camilo

Oh how I savor those words . Don't get to hear them very often. My kids wonder why I glow so much when either they or my wife says it.

It was indeed an interesting discussion and I read it all!