Highest / Lowest Torque

[BrickPilot]

Shopping for a torque wrench and need to know the lowest (in/lbs) that I'm going to need to measure/torque, as well as the highest (ft/lbs) - for building an RV-7A. Thanks in advance.

 

[Kevin Horton]

Shopping for a torque wrench and need to know the lowest (in/lbs) that I'm going to need to measure/torque, as well as the highest (ft/lbs) - for building an RV-7A. Thanks in advance.

You'll need more than one wrench to cover the whole range. The highest torque might be your prop bolts, and that torque value will depend on which prop you have, and which size bolts it uses.

You'll want to cover from 20 in-lb up to at least 200 in-lb. Depending on the prop you use, you may need to go quite a bit higher.

Torque wrenches are not very accurate if the torque value is a small fraction of the max value that the wrench can handle, so one wrench should not be expected to cover the whole range. You should avoid using a wrench to set torque values below about 20% of its rated max value. One wrench that is good for 50 to 60 in-lb, and another one good for 200 in-lb will get you started. You can buy or borrow another one later for the prop, if required.

 

[jlfernan]

I bought a Proto brand, dial type torque wrench from Grainger. I have read many stories on this site of people not hearing or feeling the "click" and breaking bolts off. The dial is a no brainer. Watch the needle climb to the desired torque, then, stop. As for not always being able to see the dial, this is true. I've learned to put my inspection mirror in a strategic place so I can see the dial. I have yet to break a bolt. As they say(whoever "they" are?) your mileage may vary.

 

[Jekyll]

Another approach: buy a 25-250, add a 12 inch extension and you have a 25-500 inch pound range.

You can use adapters to increase OR decrease the applied torque to expand the torque range of any torque wrench. FAA Circular AC 43-13-1B gives the appropriate formulas. By investing a few minutes of math, one can generate a table for thier torque wrench with various adapters.

I use a small beam 0-200 for checking run-on torque and a 25 -250 clicker for everything else. With an extension, I can easily apply more torque. I haven't done my prop bolts yet.

Jekyll

 

[BrickPilot]

Thanks all. I bought a 60-600 in/lb SnapOn electronic torque wrench, and the Proto (above) in the 0-90 in/lb range for the smaller torque stuff. Cool thing is that both will light up and beep at me when the desired torque is reached. No missing the click.