While in high school, my after school/Saturday/summer job was in an automotive machine shop that rebuilt large gas and diesel engines mostly for the government, big 6 cylinder Continentals, Hall Scotts, Cummins, Molines, Detroit Diesel and others. I usually reworked cylinder heads, which included doing crack testing using compressed air blown into the water jackets, plugging all the normal holes and then spraying a soapy water mixture on the head in areas that often cracked. If the air leaked through a crack, I got bubbles, marked the cracked area and then Magnafluxed it. The heads had expansion plugs in them that were designed to pop loose if the engine got too hot, sort of a fail safe against cracking something expensive.
To make a long story short, when a plug leaked air, often it just needed to be tightened deeper into it's threads. The plugs had a square hole in the top surface that were the sizes of socket ratchet wrench drives, mostly 3/8" and 1/2" I would use a ratchet to tighten the plugs.
One cylinder casting had a plug in a spot with little access room and the only way I could tighten it was with a "wobbly" extension, an extension that had basically two joints, like U joints, in it. I had to sometimes really put the torque to the plug with the wobbly and a breaker bar. That broke the wobbly fairly regularly.
I had spent my 1969 income tax refund on a nice set of Snap-On tools in a big red Snap-on chest and occasionally bought things from the Snap-on dealer who came by weekly. I would take the broken wobbly extension to him and he'd give me a new one. A week or two later, I'd break the new one and again he'd replace it. Guaranteed forever!
After breaking a half dozen of them, one day the dealer asked me to show him how I was breaking them, as nobody else broke their wobblies and, perhaps, he might have another, less costly tool that would work and not break. I showed him. I broke the second wobbly of the week right in front of him.
He got me another replacement and then said quietly, "I bet the MAC wobbly is a lot stronger than the Snap-On, try one of them," and gave me a $20 bill to buy one!
Incidentally, in the Snap-On tool driver assortment in my set was a screwdriver designed to use to adjust ignition points. About 5 inches long, hollow ground tip. It fits the sideplate and grip screws of Smith & Wesson revolvers perfectly, as well as the mixture screw on my Amal carburetors
My metric tools are Craftsman, and my Whitworth tools, I dunno the bloody brand, wot.
