I used this to increase the inside diameter of two 3.5" thick pieces of steel from .625" to .672". This allowed me to work 3/4-10. Even with a drill press that revs too high (800rpm instead of around 250rpm, which would be optimal for a piece of this size in steel) it went through both with ease. kept a light but steady stream of water on the bit to keep it cool. Would I use them for a professional business? Probably not. However, I would definitely recommend these bits for the occasional DIY project that requires large bits.