I use a portable grinder for the quite often Work , punching of rebar and sheet metal . The grinder is a fairly simple tool, all it does is spin a cutting or grinding wheel, so it's hard to see how it can be improved much. This tool greatly improves the technology of older grinders. First, the performance of this tool is excellent. Just as strong or maybe even stronger than many corded grinders. The downside of this, of course, is that it drains the batteries fairly quickly. A fully charged…