I did a little test on my Kobalt battery powered impact wrench this afternoon to see if it was up to the 150 lb-ft rating they advertise. I put a 5/8" bolt in my vice and put 2 large flat washers on it. I ran a nut down on it using my impact with a 1-1/8" socket on it. That is the same size socket that fits the bolt on my harmonic balancer. My impact wrench actually has three setting. I put it on the highest setting and let it hammer until no rotation could be detected. Then I marked the bolt, washers and nut so I could tell if they moved. Beginning with my torque wrench (18" long) set on 70 lb-ft I slowly worked my way up, 10 lb-ft at a time, until my torque wrench maxed out at 150. With my torque wrench set at 150 it never turned that nut at all. It just clicked at 150 every time I pulled on it. I used my old torque wrench to confirm the results. Man, was I surprised that something that looks like a fat cordless drill could put that much torque on a large bolt.
Next I used my 24" breaker bar to tighten the nut as tight as I could get it. I pulled on the breaker bar as hard as I could. I have no way of knowing how much additional torque I applied to the nut but it was damn tight. Then I tried the Kobalt impact to see if it could remove the nut. I had to let it hammer for several seconds but it did break the nut loose and spun it off. I'm pretty impressed with this little $100 impact (not including battery or charger). It looks like Kobalt tools will perform as advertised. For how long I don't know. 🙂