Ahhhh, so what you're trying to figure out is how much pressure and at what distance from the fastener to apply it.

First, you're correct that an extended length of handle lever on a torque wrench only increases mechanical advantage on the fastener and makes the force easier to apply - and as long as in attaching it you don't interfere with the designed ability for the beam to deflect on a beam-type wrench, your torque value for a given reading is not affected.

I would not suggest that you attempt to tighten a rotating fastener to a specified torque value by the determination of mechanical advantage and applied force. It can be done, but the force MUST be applied exactly perpindicular to the lever arm and you MUST know the exact mechanical advantage and frictional values.

If you want to try it and can afford a mistake, I THINK (not absolutely certain) that mechanical advantage can be found by the "Ratio of Circumferences" formula. One way to test the formula for accuracy would be to set a control experiment using a fastener that's easily accessed and a standard torque wrench. The radius of the nut probably should be figured to be half-way between the points and the flats (not absolutely certain about that either), and the radius of the applied force should be the point at which the middle of your hand (or whatever applies the force) holds the wrench handle. From each radius determine the circumference (radius x 2 x 3.14 - or diameter x 3.14) and divide the smaller into the larger. The result should be the mechanical advantage. Divide the required torque value on the fastener by the calculated mechanical advantage and apply the determined amount of force to the handle of a torque wrench pre-set at the required value. If the torque wrench agrees with the experiment, then the formula should translate in fairly trustworth fashion to another application.

If the correct torque value is absolutely critical and you can't get a torque wrench into place and you are working with a bolt and nut, the easiest thing is to remove them from the assembly, set them up in a fixture or somewhere where you can find the correct torque with the torque wrench. Then apply the tool you will need to use when the fastener is in place and see what the required force "feels" like - or if you must, make an attempt to measure the force - just make certain it's applied perpindicular to the handle.

If you try the circumference formula, I'd like to know how accurate it is....... and where on the fastener you have to measure to make the formula work in practice as opposed to theory.

Good luck,
Frank

Frank