I needed to adjust a timing belt tensioner to 33 lb-ft and there was no way my torque wrench would fit into the space available so I got two stiff springs from HD. Filling a 5 gal bucket with water (2 lbs for the bucket + [5 gals x 8.3 lbs/gal]) = 43.5 lbs and stretched the spring 1.09" from its rest length so the spring constant K = 40 lbs/inch. The spring was anchored on the wrench handle 7" from the center of the 3/8" drive stub so 33 lb-ft would need a right angle force of 33x12/7 = 57 lbs. As it turned out the posted max force on the spring was 61 lbs (no max length given) so it was close. I should have done this calc. before I bought the thing but it worked out. And with two springs in a package for $4 I could in principle go to 66 lb-ft or so. Next is to check the K for my weaker springs from the basement.

It turns out that this wrench must have magical properties, because after I used it the car started and ran more smoothly than before. Man, am I glad I can finally move this car out of the driveway! I figure one hour round trip to the rental place, twice, so I calculate, "Can I make the part/tool/fixture in less time?" This one was close.

When I was young and couldn't afford such luxury as a torque wrench, I and all my back yard machanic friends had a fish scale in the tool box. If you notice a set of combination wrenches all have a different length. If you use one of these and give it a reasonable pull, you will be really close on the required torque for that size of bolt. The reason they give you a required torque is because an impact wrench can dammage aluminium parts you are bolting into.