🪚 Metal JNBPRO Countersink Drill Bit Review

I am new to the JNBPRO brand but have ordered some of these bits for use in several projects I am making. They arrived in the blister pack pictured and I tested them before using. The markings on it are very clear and the waves of each nozzle were perfectly straight. The grinding on these is decent. Not great, not bad, but good enough. So far I've used them in 1/4" steel, aluminum rod and plate, and 3/8" stainless steel. They got the job done every time with no issues. Although they had marks…

HSS doesn't inspire me much confidence, although it's a cobalt mix I have to admit I've looked at the top sellers in this category and they all have very rough edges on them. When countersinking metal holes, I assume manufacturers understand why they create a smooth glass cut when it's only going to be covered with a cone head screw anyway. Update: This is actually because the explosion photo exaggerates the drag marks. They are relatively smooth to the naked eye. In the milling world, HSS bits

If you plan to use some countersinks just for rough work, they work fine for a while. I can't confirm the 5% cobalt claim, but assuming it's true they should hold up better than regular M2 HSS in harder steels. toothy, with the root of each tooth, a stress climber. So the line breaks off pretty quickly. This means fast matting of hard materials. The solution to the problem is a finer polishing of the edges, which unfortunately for most of us can only be done by the manufacturer. It's not…