I've used them to drill holes and threads in mild steel panels for power distribution boxes I have, I use for something other than circuit breakers . This meant using the average range of those clicks: 10-24, 10-32, and 12-24. I will have a future for others and I am also buying the following sizes to support this cause. Using a power driver (Milwaukee 12V, Lithium) allowed me to go through mild steel with cutting fluid in a relatively short amount of time. . Threading with a screwdriver takes a lot of patience and some skill, and if you have scrap to practice with I suggest you do that first as you can easily carve threads with a screwdriver. What I actually did was go to a hand ratchet screwdriver that accepts hex bits, and then tap by hand after I drilled the first hole (stop about 1/3 of the way up where the first bit is on appears on the bit). Since hand threading is more reliable to me, and with the help of cutting fluid and cleaning after each hole with a phosphor bronze brush to remove material from the threads, I was able to quickly insert a good dozen threaded holes per bit. less time than it took me to drill and tap separately (although the tapping was done with a cheap set of low-end taps that eventually saw that the target taps I use most couldn't do much anymore). Patience and attention to the condition of the thread, stepping back when needed to clean the bit and then slowly coming back to finish the job is something I'm used to and having these taps on the hex bit was a big help. I didn't find this set any more brittle than the individual taps and they seem to wear out a bit better than the cheap blue box set I've picked up here and there for odd jobs. Even with the faucet threads and threaded hole cleaned, the first screw seems to find a little more debris in the way than I'd like: somewhere, some small debris isn't being properly removed. The actual holes are a bit loose but that is not a problem given the application to relatively thin plate and sheet as the threads just need to hold and they do an excellent job. ADVANTAGES - Good range of electrician faucets. Work - Good cutting speed for the drill section, use cutting fluid - Good taps and remember the basics of moderate force and loosening for clean threads MINUS - Admittedly a little pricey hence a star goes - Use a good nylon tube brush to clean Threaded holes, as fine particles remain. If you already have a decent set of taps, you probably won't need these unless you put them in your toolbox to do the quick tapping job. This set is perfect when you're making a few holes for electrical work or just want to put something in and don't have access to a full set of indexed drill bits and taps. Worth buying! However, the metric set is too expensive for my blood, so I will have to do it in parts for some time.