By Martin Harris.

Floor Sweeps for Dust Collection

A dust collection floor sweep is a wide, low inlet at floor level that connects to your dust collector. You push shavings to it with a broom, open its gate, and the collector pulls the pile away. There is no dustpan to fill and dump.

A floor sweep needs its own blast gate, it steals airflow from your tools if you leave it open, and it will happily swallow screws that can spark when they hit the fan. Good placement, a closed gate, and a magnet solve most of that. This page covers each piece. For the bigger picture of planning branches and gates, see my dust collection system design guide.

How a floor sweep works

A floor sweep is the end of a branch line. Instead of connecting to a machine, the branch ends in a flat opening that sits on the floor or against the base of a wall. The opening is wide so you can sweep a pile straight into it.

Rockler's Dust Right Floor Sweep with Blast Gate is a typical fixed sweep. Rockler lists it at just over 18 inches wide with a front opening 2-3/8 inches high. It takes a standard 4 inch hose, and it can mount flat on the floor or upright at the bottom of a wall.

The other style is handheld. A wide nozzle goes on the end of a 4 inch hose so you can reach under benches and into corners. POWERTEC's 4 inch floor sweep is one example. A handheld sweep is handy, but it adds flex hose, and flex hose costs airflow.

Either way, suction only works right at the mouth. Air speed drops quickly as you move away from any opening, so a floor sweep will not pull dust from across the room. You still sweep the pile to it.

Where to put it

• Near the tools that drop the most chips on the floor. In most small shops that means the planer, the jointer, and the table saw. See my guides to planer and jointer dust collection and table saw dust collection for catching more at the machine in the first place.
• On a short branch. Every foot of duct and every fitting adds resistance. A sweep placed close to the collector, or close to where the main line passes, gets more air when you open it.
• Out of the walking path. Mount it against a wall or at the base of a cabinet so nobody trips on it and the broom has something to push against.
• Joined to the main with a wye. A wye brings the branch in at an angle and loses less air than a tee. My dust collection fittings guide compares them.
• Where you can reach the gate with your foot. If opening the gate means crouching down, you will skip the sweep and grab the dustpan.

The blast gate it needs

A blast gate is a sliding plate that opens or closes a branch. A floor sweep needs one because its opening is large and unrestricted. Rockler's sweep opening works out to about 43 square inches. A 4 inch pipe has about 12.6 square inches of area. So an open floor sweep has more than three times the opening of a 4 inch duct, and it will pull a big share of your collector's air before any tool gets it.

Keep the sweep's gate closed any time you are not sweeping. Rockler builds a foot operated gate into its sweep for this reason, so you can open and close it without bending down. My system design guide makes the same point for every branch: each open gate splits your airflow, and too many open gates starve every tool at once.

You have two places to put the gate.

• At the sweep. This is easiest to use, especially with a foot gate. The downside is that the branch pipe between the main and the sweep sits as a dead end when closed, and fine dust can settle in it.
• At the wye on the main line. This leaves no dead pipe, but the gate may be overhead or out of reach. Some people put a gate in both spots.

Whichever spot you pick, choose a gate that seals well. A leaky gate on a sweep bleeds air all day. My best blast gates roundup compares seal quality, and how to install blast gates covers placement and mounting.

What a floor sweep costs in airflow

A floor sweep costs airflow in two ways. The first is an open or leaky gate while a machine runs, which I covered above. The second is the branch itself. The pipe and fittings between the main and the sweep add static pressure, the resistance your collector's fan has to push against. Static pressure is measured in inches of water column, written as in. w.c.

Here is Oneida's published loss data for the fittings a sweep branch usually needs, measured at about 4,000 feet per minute (FPM).

Values in inches of water column. Source: Oneida Air Systems static pressure component data, measured at approximately 4,000 FPM and sea level.

As an example, a 4 inch sweep branch with 10 feet of rigid pipe, one wye, one 90 degree elbow down to the floor, and 2 feet of flex adds up to about 2 in. w.c. That is 0.57 for the pipe, 0.375 for the wye, 0.45 for the elbow, and 0.56 for the flex. Drop the flex and you save more than a quarter of that. My static pressure loss calculation guide walks through a full system the same way.

How you use a sweep works in your favor. You sweep with your machines off. With every other gate closed, the sweep branch has the collector to itself, so a modest branch loss rarely matters. What hurts is leaving that gate open, or leaky, while a machine runs.

Magnetic sweeps and grates

Anything on the floor goes into a sweep, including screws, nails, and staples. A magnet across the mouth catches steel before it enters the duct. Bill Pentz describes gluing large neodymium magnets onto the front of his floor sweep to collect nails and screws before they get sucked up.

You can also buy one. Rockler's Dust Right Magnetic Floor Sweep Attachment uses ceramic magnets and fits Rockler's Dust Right floor sweeps. Rockler says it filters out ferrous metal parts before they reach the collector, which protects the impeller. The impeller is the spinning fan wheel inside the collector.

Know the limits. A magnet only holds iron and steel. Brass screws, aluminum parts, and small stones pass right by it. Laguna's collector manual warns against letting steel or rocks strike the impeller, since either can make sparks. Clear the magnet often, because a loaded magnet catches less.

A grate over the opening stops offcuts, rags, and gloves that could jam a 4 inch branch. It will not stop screws, so a grate and a magnet do different jobs. Do not confuse magnetic sweeps with magnetic dust collection fittings, which are quick connect hose ends held together by magnets.

Automatic floor sweeps

People mean two different things by an automatic floor sweep. The first is the toe kick dustpan sold for house central vacuum systems. It fits into a slot cut in a cabinet base, and tapping a lever with your toe opens it and starts the vacuum. These are made for central vacs, not for a 4 inch woodshop dust collector.

The second is a shop floor sweep tied to your collector's power, so the collector starts when you open the sweep's gate. You can get there with an automated blast gate system or a switch on the gate, and a remote switch covers the simpler version. My guides to automatic blast gates and dust collector remotes cover the hardware.

One caution with any automatic start. A collector that turns on by itself can surprise you. Laguna's manual warns to keep hands and tools away from an open collector inlet during operation. Keep broom handles and fingers clear of the sweep opening when the gate is open.

Hazards and how to handle them

• Metal hitting the impeller. On a single-stage collector, everything passes through the fan. Woodcraft notes that even a small screw can cause a spark when it hits a steel impeller, and Bill Pentz warns that a screw or nail picked up this way can put a spark in the collection bin. See single-stage vs two-stage dust collectors for how the designs differ.
• Smoldering dust. Laguna's manual says sparks can smolder in wood dust for a long time before anyone sees a fire. If you know metal went in, it says to turn off the collector, unplug it, wait for the impeller to stop, and empty the container into an airtight metal container.
• Relying on a separator alone. A cyclone or baffle separator drops heavy debris into a bin before the fan, which keeps most metal off the impeller. The metal still lands in a bin full of dust, so keep the magnet. My best dust separators page and Thien baffle build guide cover the options.
• Flammable or wet material. Laguna's manual says not to collect metal, liquids, or flammable materials. Keep finishing rags and solvent soaked paper towels out of the sweep.
• Clogs. Long offcuts, gloves, and pencils can wedge in a branch. A grate helps, and so does sweeping large pieces aside by hand first.
• Full bins. Laguna's manual recommends checking and emptying bags or drums regularly, since built up fine dust raises fire risk. Dust collector bin liners make that job faster.

Static in plastic duct comes up in the same conversations as floor sweep fires. My page on grounding PVC dust collection pipe sorts out what the evidence says. For every other part of a small shop system, see my guide to dust collection for small shops.

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