Torque Adapter Formula (Crows Foot Addition)

I ran across a few useful torque facts on CDI's torque tool website while searching for a torque calculation when adding a crows foot to tighten flare nuts.

www.cditorque.com

Keep in mind you will more than likely be measuring inch pounds not foot pounds. Below is a screen capture with the formula for adding an adapter to a torque tool:

Chuck

That's not a "crows foot", that's an extension. The classic crows foot is less than an inch long and requires no correction value. Also, of you attach an extension ( no matter how long) at a 90 degree angle to the handle, you zero out the effective length of the adaptor and also need no correction factor applied.

Torque Adapter

The drawing does show an adapter. Extension, crows foot, tube wrench etc. are all termed adapters. However, any adapter that is added to the end of a torque wrench needs to be considered mathmatically. I was trying to present the formula and some awareness of adding such a device to a torque tool. Even a one inch extension will change the torque value by 8% using a 12 inch wrench.

Given the following:

12 inch torque wrench
1 inch adapter (crows foot)
100 inch pound torque requirement

(12 x 100) / (12+1) = 92 inch lbs (Delta -8%)

Chuck

I don't like to trust my math skills (laziness enters into it also), so I just find that putting it on at 90 degrees takes out all the guesswork.

Toobuilder said:

That's not a "crows foot", that's an extension. The classic crows foot is less than an inch long and requires no correction value. Also, of you attach an extension ( no matter how long) at a 90 degree angle to the handle, you zero out the effective length of the adaptor and also need no correction factor applied.

Click to expand...

cka357 said:

... Even a one inch extension will change the torque value by 8% using a 12 inch wrench...

Click to expand...

I theory, yes, even the standard crows foot you will find in a toolbox will act as a slight lever, but general military practice is to ignore anything under 1 inch.

...and if it's good enough for a $30m airplane carrying Nukes...

Allan, want to take this one?

Sorry couldn't help myself. All in good fun, and a happy customer.

There are two ways to use a crows foot, you can use it as an extension or as a reduction and the maths will be different. By as a reduction I mean putting the crow foot back towards the torque wrench handle.

Actually, as has been mentioned, there are 3 ways to use it. Extension (math required), Reduction (math required) or 90 degrees (no math required).