An end mill holder is a tool used in machining to securely hold an end mill, which is a type of cutting tool. These holders are designed to fit into a milling machine's spindle, allowing for precise cutting and shaping of materials like metal and wood. They come in various sizes and styles to accommodate different end mill types and applications. End mill holders can be made from materials such as steel or aluminum, providing durability and stability during operation. They often feature a locking mechanism to ensure the end mill remains firmly in place, reducing the risk of tool slippage and improving overall machining accuracy.