Very durable. I have bought several brands of spot weld cutters. These are by far the best, i've cut about 100+ spot welds without breaking or going through one cutter yet (14 cutters left). You will not be disappointed.
I use these for old school muscle car restoration with metal distortion and rust, and they work well. Originally bought them for the price. Very impressed.
I have used a lot of these over the years but I can legitimately say these are the toughest I have found. Normally I can get a few welds cut before I am changing a cutter. I bought two kits thinking I would need all of them. Now I am convinced I will have several leftover when this project is done.
This little guy made things easy.
Perfect size for camloc fasteners and cuts cleanly into carbon fiber engine cowls. Mandrel and pilot were much smaller than I expected, but plans were made for adapting I guess. I had to make a conical bushing to adapt the smaller pilot to my template that already had #30 holes. Even so, the project went a lot faster and more accurately with this than the last time where I used a dremel, so big win for me.