While crude, it’s a universally understood method of how hard it’s going to take to get a bolt or lug nut off.
You’ve probably heard the term “ugga dugga” used when someone is jokingly describing how hard it is to take off something when wrenching on a car. For example, “Yeah, that stubborn piece of you know what took about five ugga duggas to take off.” An Ugga Dugga is a unit of measurement of power that replaces time with the actual word “ugga dugga” and the torque rating of a pneumatic or electric impact wrench as the work.
“Ugga duggas can be counted infinitely, but we commonly understand that 5 Ugga duggas is the maximum for torque, while three Ugga duggas is sufficient to hold most projects. To count an ugga dugga…you squeeze the trigger of your impact gun and count off, “One Ugga Duga, Two Ugga Dugga etc.”
In equation form, if power= work/time, you can replace time with ugga-dugga.
Why Ugga Dugga?
Ugga Dugga is a word that replicates the sound of an impact gun (onomatopoeia.) Impact wrenches or guns work by spinning a rotating mass, storing that mass energy (often in a spring) and delivering that energy in a hammering effect against an output shaft.Embed from Getty Images
The amount of torque delivered per hammer blow over time is more than a human can deliver over that same time period. Delivered at an average rate of 50 hammer strikes per second, impact guns deliver massive amounts of torque quickly.
Cordless impact wrenches typically deliver around 500-700 lb-ft of nut busting power, while more capable air impact wrenches connected to air tanks can deliver upwards of 1,000 lb-ft and beyond.
The gif below taken from this video linked here describes,the basics of impact gun operation.
Ugga Duggas are not a professional unit of measurement
Just to be clear, Ugga Duggas are sort of an inside joke. No professional mechanic would actually use the “ugga dugga” method when working on a car.
Impact guns are powerful, time-saving tools,but are often used by inexperienced mechanics in a hurry in places where they really should take their time or use less powerful tools.
For example, impact guns, while used to tighten wheel lug nuts, can be used incorrectly when used too long. This can over-tighten a bolt, or worse, strip it. A passing mechanic can then jokingly comment, “How many ugga duggas did you use to tighten that one?”
Another example is a new lube mechanic who usijg an impact wrench to tighten an oil drain plug. Oil drain plugs usually only need 20 lb-ft of force to tighten a quarter turn. You can imagine said lube tech using an air impact wrench rated at 700 lb-ft using “ugga duggas” to tighten that drain plug, stripping the threads and causing an even larger problem requiring either a thread repair or new oil pan.
Here are some photos of car guys who used “Ugga Duggas, but it went too far.”
Knowing this, Ugga Duggas should only be used in jest when actually working but can be used freely to describe how hard taking something off was among friends and fellow professionals.