Hobby CNC machines typically use either a spindle or a router. While these two devices appear similar, they each have distinctly different characteristics.
A router is commodity hardware, and may be found in any hardware store such as Lowes or Home Depot as well as online stores such as Amazon. Routers are typically used to cut wood, and are particularly useful for cutting slots and other patterns into wood. There is a vast variety of different shaped router bits designed to create different patterns in wood, although these bits are generally not useful for CNC applications.
Advantages of a router
Routers are cheap and powerful. You can easily buy a nice, 2.25 HP router for less than $200. Good routers typically have an adjustable speed, and generally reach speeds of 25,000 or even 30,000 RPM which is ideal for cutting wood at a high rate of speed.
Disadvantages of a router
Routers are generally very loud, and generate plenty of noise when cutting material. The more load you apply to a cutting bit powered by a router, the slower the bit will go which leads to finishes that aren’t quite as nice as what you’d like it to be. Because routers are meant for cutting wood, there can be some problems when attempting to cut aluminum. Routers can be very loud when cutting aluminum, and there is generally a bit of runout which is not desirable. Often, a router’s minimum speed is 8,000 RPM or 10,000 RPM which is really too fast to cut aluminum without destroying your cutting tool and having a poor finish on your aluminum piece. So unless you’re only doing light engraving in aluminum, a router may not be the right tool for the job.
Advantages of a spindle
Spindles are more versatile than routers. The speeds can vary greatly, and are typically controlled with a digital VRM module allowing you to set the exact speed you’re looking for. Even under load, the speed of a spindle should be fairly constant which give your piece a nice finish. Another huge advantage of a spindle is the noise it generates. Spindles are known to be more quiet than routers when cutting materials. If you have neighbors nearby, a spindle may be better for you. Finally, a spindle has less runout than a router does, making it more ideal to cut precise metal parts than a router could do.
Disadvantages of a spindle
The main disadvantage of a spindle is the price. A good spindle can easily cost a thousand dollars or more, and cannot be found at a local hardware store. So if price is king for your hobby CNC project, a spindle may not be the right choice for you. You may be able to find some cheap but okay quality spindles from Chinese sellers on eBay also. That is usually where I buy linear rails for my machines and it works out okay. Another disadvantage of a spindle is that it is advised you warm up the spindle for a few minutes prior to cutting material. In addition to that, it is recommended that you keep the spindle running if you just have a short amount of time between cuts. This warm up time is not required for routers.