Jon Siegel replies: Your problem may not be lack of horsepower, but simply ducts that are too small. For any major machine, or for use at a lathe, I recommend 5˝ diameter ducts. There is a huge difference between 4˝ and 5˝ ducts—56% more! It is also important that the impeller has enough volume capacity to produce sufficient velocity within the 5˝ duct to prevent particles from falling out of suspension and the filtration system does not impede the flow. So it’s not all about horsepower. All parts of the system need to work in balance.