Which Dust Deputy Cyclone Do I Need?

We do not typically assign CFM ratings to our cyclones as the CFM spec listed for dust collectors in the market are highly inflated and not realistic. We recommend that customers try to align their cyclone purchase so that the inlet of the cyclone is the same diameter as their dust collectors inlet. This provides for the best match. However, if you are finding that dust is completely bypassing the cyclone's dust bin, then you most likely have an air leak in your system. Any air leak, even small pin-prick holes, can interfere with the cyclone's pressure system. We recommend using a smoke stick or lit incense stick to try and identify where the leak may be. Common locations are the lid of the cyclone's dust bin as well as any part where components meet (i.e. hose connections, reducers, etc.).

For tools with their own built-in blower fan (such as the Dewalt 735 planer mentioned in another comment) we sometimes recommend that customers try using the cyclone as a positive-pressure system. In that system you do not use suction to pull air through the cyclone but you instead blow air into the inlet instead. The reason for this being that if you have a blower and a vacuum working on the same system they can "fight" against one another. In this example the vacuum is still hooked up so you can utilize it's air filter, but not turned on. Other customers have sealed a vac filter on top of the cyclone directly (but only when they're only using the cyclone on that blower system). That being said, sometimes the vacuum is powerful enough to overcome this anyways. Here's an example of a standard installation with the Dewalt planer from Trull Gallery: https://youtu.be/OTSSFu7O8J8