At first glance there isn't much about this set that grabs your attention. The 39 piece inventory offers 17 taps and 17 dies in commonly used sizes from a #4 up to 1/2″ in both coarse and fine thread, as well as 2 tap wrenches (T and long handle), a die stock, and a thread pitch gauge, which is pretty much on par with most comparably priced sets. One thing that drew me to this set was the fact that it's made from a “High Speed” alloy steel rather than carbon steel like most budget sets. The real eye opener with this set was the fact that it's backed by A full LIFETIME WARRANTY. If you aren't familiar with Tekton's warranty I can tell you it's a truly painless process. You simply call them, tell them the problem, and they send out a replacement tool. No grilling you about where you got it, how you used it, etc. and no asking for a copy of the receipt or shipping the old one back at your expense. A warranty like this, while not as common as it once was, isn't unheard of for hand tools, but with the possible exception of the truck brand sets that typically cost hundreds of dollars, it is unheard of for Taps & Dies. The idea of getting a lifetime of T&D's for around $40 made this a no brainer as far as I'm concerned.
As I said, I'm no machinist. My T&D use is pretty much limited to the occasional scenario where existing threads are stripped bad enough that a thread chaser won't fix it. Such was the case with the air cleaner on my Cub Cadet project. The 1?4″ hole was badly stripped and a thread chaser wasn't cutting it. The relatively thin work piece didn't really give me the depth I prefer for a helicoil, so I decided to drill the hole out smooth and step it up to a 5/16. The set included a drill chart which specified using either a size F or a 17/64 drill bit, and having no letter bits, I opted to use the 17/64. Using my drill press I drilled out the hole leaving it relatively smooth and ready to tap. Using the 5/16 coarse tap, the T-handle wrench, and plenty of cutting fluid, the tap turned easily into the workpiece. This was lightweight cast steel and wasn't exactly tipping the Rockwell scale, but nevertheless, the tap breezed through it.
The finished product was very smooth and the 5/16 bolt went in smooth and fastened nice and tight.
The bottom line is that this set performed as intended. If you use T&D's routinely you're going to want a higher quality set with more pieces, etc. That being said, for the occasional user the #7558 set is going to be sufficient in the vast majority or cases. At under $40 this set will likely pay for itself in only a couple of uses versus having the work done by a professional. It isn't a professional quality set, and it doesn't offer many more pieces than most other sets you'll find for $40, but the lifetime warranty and Tekton's excellent reputation for customer service really put this set ahead of others in this price range. Tekton also offers a 39 piece metric set that goes up to 12mm (#7559) as well as bigger 45 piece sets in SAE (#7560) and metric (#7561) that go up to 1″ and 24mm respectively. All 4 sets are backed by the same lifetime warranty. As I said, this probably isn't a set for the professional user, but for the DIY/hobbyist crowd, it's definitely a set worth considering.