Tool height offsets compensate for the different lengths of tools stored in the tool magazine of the machining center. Before lab please inspect the machining center and locate the tool magazine. Since the different tool lengths may not be known to the part programmer a method similar to the cutter compensation system has been implemented. This method allows the machinist to store the height differences between the tools in a data table in the controller's memory. The height differences are all relative to a reference tool. In our case the reference tool is a dead tool. A dead tool is rod that is not used to machine parts. As shown in figure 8, tools longer than the dead tool have positive offsets and tools shorter than the dead tool have negative offsets. The memory locations for the tool offsets are designated by an "H" code. Please refer to the previous part program to see an example of the use of tool offsets.