Side lock holder is one of the industrial tools used in a milling machine. This is an endmill holding arbor comprising a grub screw for securing the milling cutter from the side into the arbor. Also used in CNC machine center, the job of this kind of tool is to hold cutter in specific diameter and roughing milling cutter with strong grip, without allowing slipping or spinning of the cutter in the arbor under heavy load. Industries that use CNC machine for milling must keep a stock of side lock holder. This tool can be easily replaced once worn.