Abstract: A hammer assembly that will mount in a grinder/shredder/hammer mill type machine. A tool holder is milled with dovetail/angular slots along each side of the hammer tool holder, which allows milled blade to slide in to place and be securely held in position. The simple milled slot located in the middle of each blade that allows a single mounting block/bolt to securely hold each blade in position. This results in the ability to rotate and/or interchange blades. The tool holder allows single or multiple blade/hammer inserts to be installed without having to remove a hammer pin, so the tool holder stays in the machine, and the blades can be easily removed. This arrangement allows the tool holder to stay in place, and enables the simple removal of a single bolt and retention block and then flip or rotate the hammer to get additional wear surfaces or install new blades.