So, lots of reviews about how bad they are. First, they are not intended for production work. They are more for light use and work quite well with proper care. I had new kitchen cutting feet that I needed but they were M4 1.5 and I needed M6 1.0, the insert was brass so I took the right piece, added some cutting oil and viola, now I have useable legs. Don't force them, use plenty of cutting fluid and take your time, and they'll make nice, clean threads in steel and aluminum. Push too hard they will break, try to push they will break, hit hard they will break, no oil. you get a picture. I found it easier for the tool to cut and back off a bit and then cut again until you're done. you work for me