Extra Parts is simple enough: it adds extra tool parts for Silent's Gems. It does not add the materials required for building tools (at least they are not craftable), so you will need other mods installed along with this one. For example, you will be able to make tools from bronze if you have another mod that adds bronze ingots (and properly registers them in the ore dictionary).
This is for Minecraft 1.9+ only. The original version of Silent's Gems doesn't allow new materials to be added, so porting this mod to 1.7/1.8 is not possible.
Extra Parts非常简单：它为Silent's Gems增加了额外的工具部件。它不会添加构建工具所需的材料（至少它们不可制作），因此您需要安装其他mods。例如，如果您有另一个添加青铜锭的mod（并在矿石字典中正确注册它们），您将能够使用青铜制作工具。