Dust Collector Basics

A dust collector should suck most of the dust and wood chips away from machines such as tablesaws, thickness planers, bandsaws, and drum sanders and then store that waste to be disposed of later. In addition, a collector filters the fine dust and returns clean air to the shop. But a collector that does only one of these tasks fails you and deserves to either be fixed with upgraded components or replaced with a better model. Don't accept poor performance—your health depends on it!

Before you begin shopping for a dust collector, answer the following questions:

■ How many machines will the collector serve? Do you need a collector for the whole shop or dedicated to one or two machines?

■ If you're looking for one collector to serve all of your machines, will you park the collector and connect it to a duct system? Or will you roll it around to each machine as needed? If it needs to be portable, then you'll need not only a model on casters, but also a floor smooth enough (and without restrictions, such as electrical cords) to allow for easy movement.

■ Does your shop's electrical service limit your options? For example, most collectors with 2-hp or larger motors require 220-volt or greater service. If you don't have adequate 220 already installed, can you hire an electrician to make this upgrade?

■ Where will the collector reside in your shop? Do you have sufficient space (length, width, and height) for the collector you want? Low basement ceilings might limit your choice of collector.

■ Will you house your collector in a closet or walled-off room within the shop? This reduces noise in the shop, but also requires return venting for airflow to exit that room.

■ Will your collector reside outside the shop? Some woodworkers install their collectors outside the shop to reduce shop noise or save the floor space. (Check your local zoning laws and ordinances first.) 

Most people have one of these long before filling out a shop with woodworking machines. These tools provide excellent suction from a 2-1/2"-diameter or smaller hose, with a tub to catch debris and a pleated-paper filter to trap dust. They work well with benchtop and portable tools, but the filter can clog quickly and reduce airflow. Upgrading to more efficient filters and disposable collection bags creates cleaner discharged air and easier debris disposal. 

Also known as a dust extractor, this vac has a built-in outlet that allows you to plug in a tool and connect to the dust hose so that powering up that tool also activates the vacuum. These units use high-efficiency filters and collection bags, so you get exceptional dust filtration. They also use more interior baffling to run more quietly than regular vacs. These units work with most portable power tools, but matching the hose nozzle with your tools' dust ports can be a challenge.

These units typically hang from the ceiling (but don't have to) and filter out the fine dust particles that hang in the air—right where you're more likely to inhale them. Clean the filters regularly to maintain good airflow. Ideally, you'd get two units with at least 600 cubic feet per minute (cfm) airflow for a typical two-car-garage shop, or one unit with double that performance. This circulates the air to keep dust suspended and filtered quickly. Even an undersized unit is better than none at all.

Dust collectors fit into either of two categories: single-stage or two-stage. Both types use a motor-powered impeller (a fancy word for fan) with vanes (blades) contained in a metal housing to create airflow (suction). But these types of collectors differ in how they handle incoming dust-laden air.

Single-stage machines suck air through a hose or duct directly into the impeller chamber and then blow it into the separation/filtration chamber. See the illustration above In most cases, the collection bag mounts beneath the filtration bag or canister. As the dusty air loses velocity, the heavier particles settle in the collection bag. The finer particles rise to get trapped as the air passes through the filter media. 

Single-stage collectors work well when matched to the appropriate combination of tool and hose/duct, below. One downside: Since all debris passes through the impeller, any knots or stray hardware could damage the impeller vanes or the plastic or cloth bags.

A two-stage collector works differently. The impeller sits on top of a cone-shaped separator (shown above), sucking the dusty air directly into that separator. As the air spirals inside the cone it slows, allowing most debris to settle into the collection bin. The finer dust travels up the center tube within the cone to the impeller and then into the adjacent filter. So, no debris other than fine dust ever reaches the impeller. Larger collectors have larger components (motor, impeller, separator, bin, and filter) which translates into greater airflow, suction, and storage.

  1-hp Single-Stage

* These units mount to a wall or on casters.
* Outfitted with just a single 4" inlet.
* The collection bag often doubles as the filter bag, so it loses effectiveness as it fills up. Bags typically consist of 5- to 30-micron cloth (see Don't Skimp on Filtration, below) and can be messy to dump.
* Models with a pleated canister filter use a plastic collection bag.

  1-1/2-hp Single-Stage

* These models use caster bases for easy mobility.
* The 5–6" inlet includes a wye fitting with two 4" ports.
* Separate filter and collection bags make for better, more consistent airflow and easier dumping.
* Most new models use disposable plastic collection bags (a cost-cutting feature); older versions have reusable cloth bags.
* These units sell with cloth filter bags rated at 30 microns or less, or pleated canister filters rated at 5 microns or less.
* Some models add a deflector in the collection chamber to slow and separate debris.

  3-hp Single-Stage

* Casters allow portability, but these units generally remain stationary, hooked to a duct network.
* The 6–8" inlet includes a fitting with two or three 4" ports.
* With double filter and collection bags, these produce greater airflow and storage; filters usually rate at 5 microns or less.
* Collection bags often fill unequally, but you can run this unit until both are full, although airflow might decrease.
* Some models add deflectors in the collection chambers to slow and separate debris.

  1-1/2–2-hp Portable Two-Stage Cyclone

* Casters make these units easy to move.
* The 6–8" inlet includes a fitting with two or three 4" ports.
* Some models have automated baffle cleaners for the pleated filters; filters typically rate at 2 microns or less.
* These units typically feature a remote-control start.
* The collection bin often comes with disposable plastic liners for easier dumping. A small bin means more frequent dumps, especially if connected to a planer.

  3–5-hp Stationary Two-Stage Cyclone

* These models stand on a metal base or mount to a wall.
* The 7–8" inlet sometimes includes a fitting with multiple 4" ports.
* Some models have automated baffle cleaners for the pleated filters; filters typically rate at 2 microns or less.
* These units typically feature a remote-control start.
* The collection bin usually comes with disposable plastic liners for easier dumping.
* These collectors can stand 8' or taller, especially when using a 55-gallon collection bin.

A dust collector pulls air through hose or duct at an airflow volume measured in cubic feet per minute (cfm). The more cfm a collector can generate, the farther it pulls dusty air. But as that airflow encounters resistance in the hose or duct, it loses velocity and efficiency, and in extreme cases, the dust settles out of the airstream inside the duct—creating a potential clog. Resistance, measured in inches of static-pressure loss (SP), results from many things:

* tight turns, such as 90° elbows
* too many elbows, wyes, or directional changes in duct or hose;
* duct or hose too small in diameter for the airflow generated by a collector;
* ribbed flex-hose (like driving on a bumpy road);
* stepped (rather than tapered) reducers.

There's no way to increase a collector's maximum airflow—that's a fixed figure. But you can help your collector perform at its best by minimizing restrictions in the hose and duct. Use as much straight, smooth-walled duct—of equal diameter to your collector's inlet—as possible with the absolute fewest elbows and wyes needed. Use two 45° elbows instead of one 90°; the gentler curves won't restrict airflow as much. And limit flex-hose to the shortest lengths possible, or use smooth-wall flex-hose. Too many open blast gates (or hoses without blast gates) divide airflow among different duct runs rather than maximizing airflow in a single duct.

As an experiment, we set up a temporary duct system in the WOOD® shop and tested seven types of dust collectors in real-world and scientific trials. We used machines representative of their type, not necessarily the best machine in each group. We started with a 20'-long, 6" schedule-40 PVC trunk (photo, above) and added several configurations of 4" drops, purposely adding some airflow-robbing restrictions. We measured airflow at each drop with the other blast gates closed (shown in the chart below), and with various scenarios of two or three gates open. We also connected a benchtop planer and a drum sander at each drop and ran boards through them to check the collectors' ability to suck up wood chips and fine dust in real time. Even though we included a few no-nos (90° elbows, too many gates open), we were surprised at how well so many collectors performed.

NOTE: Airflow measured in cubic feet per minute (cfm) in 6" PVC trunk with 4" drops and seasoned filters on each collector

As you'd expect, the 3-hp machines performed superbly, and the 2-hp portable cyclone fared nearly as well. Even the1 1⁄2-hp single-stage collector sucked up all the planer shavings we could throw at it—using 12"-wide pine!—from all three drops, something we did not expect. We also gave the 1-hp collectors a chance, but they simply lack the oomph for this duct setup, shown above. 

For our second test, we reduced the main trunk to 4" PVC. Even though all of the dust collectors suffered a drop in airflow, most could still suck up the planer shavings—the most demanding task—from each drop. 

Our tests revealed that you might not need to buy a pricey 3-hp cyclone to handle the duct system in your shop, even though it would most likely work the best. But you also don't want to push a collector beyond its capabilities, or short yourself on future shop growth. Bottom line: Buy a collector capable of maintaining sufficient airflow while overcoming the restrictions in your ductwork.

Once the dust and debris is in your collector, make sure it stays there. The worst thing you can do is allow your collector to blow the ultrafine dust through the filter media back into the shop air where you'll breathe it. Many collectors come with filters rated to trap dust particles as small as 5 microns, with some even down to 1 or 2. Also, check the manufacturer's stated efficiency, such as "captures 95 percent of particles as small as 5 microns." Don't accept anything higher than a 5-micron filter with a high efficiency rating! If your collector has a filter rated worse, buy an aftermarket replacement that will keep your air cleaner (americanfabricfilter.com). 

Filters come as cloth bags or pleated paper canisters, and both work well (up to their rating). As dust builds up inside the filter—seasoning it—that dust actually helps to trap more fine dust particles, but at the cost of reducing airflow. You can knock that dust off with a built-in cleaner (on canisters), or pat the inflated bag with your hand. The filter will never be as clean as new, but you'll find the right balance over time. 

Sources:
Grizzly: 1-hp single-bag collector, no. G1163P; 1-hp two-bag collector, no. G8027; 3-hp collector, no. G0562ZP; 1-1/2-hp portable cyclone, no. G0860; grizzly.com.

Jet: 1-1/2-hp Vortex Cone collector, no. DC-1100VX-CK, jettools.com.

Laguna: 2-hp portable cyclone, no. C|Flux:2, lagunatools.com.

Oneida: 3-hp V-System cyclone with 55-gallon drum, no. XXVM003, oneida-air.com.