There are two main types of dust collectors: single-stage and two-stage. Two-stage collectors draw air first into a separator, where the chips and larger dust particles settle into a bag or drum before they reach stage two, the filter. That keeps the filter much cleaner and free flowing, improving suction. That means a two-stage system can accommodate a much finer filter than a single-stager, which is better for your lungs.
The most effective kind of two-stage system is the “cyclone,” which uses a funnel-shaped drum as the separator, or first stage. Dust spins around the outside, which gives bigger particles more of a chance to settle out before the smaller stuff escapes to the filter stage. If you can afford one, buy a cyclone dust collector. The first cyclones for small shops were big, expensive, stationary machines, requiring long hose or rigid-duct runs to reach all four corners of a shop.
If you can’t afford a cyclone dust collector, buy the most powerful single-stage collector you can afford, with a bag or cartridge filter that will trap particles as small as 2 microns. Connect it to every machine in your shop. If it is big and powerful, you can connect it to multiple machines permanently, using a series of hoses and junctions, with blast gates to direct the airflow where you need it. With a smaller collector, you can roll it around and connect it to the machine you’re using. Long hoses sap suction, so keep the hose short with smaller dust collectors.