We do a lot of sanding in our prefinishing shop, and the fine dust often clogged the filter on the shop vacuum. Cleaning the vacuum filter was messy and time-consuming, so I looked for an alternative. After considering expensive commercial filters, I decided to build my own out of medium-density fiberboard (MDF) and a 1-in.-thick fiberglass furnace filter.

Whatever size filter you choose (some are rectangular, some square) build the box around it for a tight fit. Holes in the top of the box receive the hoses from the sander and the vacuum, one on each side of the filter. The filter slides in from the front between wooden cleats. The door, attached with hinges, locks with screen-door hooks and eyes. I caulked all joints in the carcase and put a rubber gasket around the door to make it airtight.

I was surprised how well this simple and cheap device actually works. The vacuum filter still clogs, but now I clean it weekly instead of daily. A light tap on the furnace filter every few days helps keep it clear.

Drawing by Jim Richey.

Drawing by Jim Richey.

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