A router table is two dust sources bolted together. The fence catches the chips thrown sideways off the cutter; the enclosure under the table catches everything that falls and everything the fence missed. Connect only one and you will keep sweeping.
This surprises people because a handheld router has one obvious problem — chips everywhere — and a table seems like it should be tidier. It is tidier, but only if both halves are collected, and the two halves want different things from the machine on the other end of the hose.
The fence port: high pressure, small hose
The fence port sits within an inch or two of the cutter, in a small enclosure, with a small opening. That is textbook shop-vac territory: high static pressure through a 2-1/2 in. hose, pulling hard on a small volume. A dust collector connected here does surprisingly little, because a collector's strength is moving a lot of air at low pressure and there is no volume for it to move through that opening. Our shop vac versus dust collector piece works through why.
Two things determine how well the fence port performs, and neither is the vac:
- How closely the fence faces close around the bit. Most router-table fences have sliding sub-fences precisely so you can bring them in until they nearly touch the cutter. Every inch of gap you leave is an inch of air that gets pulled in instead of chips.
- Whether the port is behind the cutter or above it. Chips leave the bit roughly tangentially. A port directly behind the cutting zone catches them; a port high on the fence catches the fine stuff and lets the chips bounce.
Under the table: high volume, big hose
The space below the table is the opposite problem. It is a large box with a large volume of air in it, and what you want is to move that whole volume steadily so falling material is carried out rather than settling on the router motor. That is a dust collector's job, through a 4-inch port, not a vac's.
If your table is an open stand with no enclosure at all, the single highest-value improvement is to box it in. A plywood or MDF cabinet with a 4-inch port in the back turns an open frame into a collection chamber, and it also drops the noise noticeably. It does not need to be airtight — in fact it should not be, because the collector needs make-up air from somewhere — but it needs to be enclosed enough that the airflow has a direction.
Watch the reducer trap here. A 4-inch cabinet port stepped down to 2-1/2 in. to reach a vac throttles the whole thing to the small pipe's capacity: about 136 CFM at the velocity chips need, against 349 CFM for the 4-inch line. Those figures and the arithmetic behind them are in our CFM and duct chart.
Running both without buying two machines
The honest ideal is a vac on the fence and a collector on the cabinet, running together. Plenty of shops do not have both, so in descending order of how well they work:
- Vac on the fence, collector on the cabinet. Each machine does what it is good at. This is as good as a home router table gets.
- Collector on both, via a wye.Works, but the collector will preferentially pull from whichever branch offers less resistance — nearly always the big cabinet port — so fence capture suffers. A blast gate on the cabinet branch, closed part way, helps more than it sounds like it should.
- Vac on the fence only. Better than it sounds, because the fence is where most of the volume is generated on edge work. The cabinet fills up and you vacuum it out periodically.
- Vac on the cabinet only. The weakest of the four. A vac cannot move enough air through a large box, and you have left the chips at the cutter uncollected.
Whichever you run, put a separator in front of the vac. Router work produces a genuinely startling volume of chips for the size of the tool, and a vac filter on router duty without a separator will load in one session.
The cut where none of this works
When the bit is buried in the fence — a rebate cut with most of the cutter shrouded — collection is excellent. When the bit stands proud above the fence, as it does on large panel-raising cutters, the fence port is capturing only part of what is thrown, and there is nothing above the cut. Those are also the cuts that generate the most material.
The mitigation is a fence with an over-cutter guard that has its own port, which some aftermarket fences include. Failing that, this is the cut where a respirator stops being optional, and a good argument for running an air filtration unit during and after the session.
Large panel bits are also the ones with the strictest speed limits — a 3-1/4 in. cutter is not safe at trim-router RPM. The published figures are in our router bit speed chart.
If you are still choosing the table
Dust collection provision varies a lot between router tables and is worth weighing when you buy: whether the fence has a port at all, what size it is, whether the fence faces slide, and whether the stand is enclosed or open. Our router table roundup covers the field, and which router to buy covers whether the motor you own can even be mounted under one.
What we could not verify
We have not measured capture rates at any fence or in any cabinet, and we found no published CFM specification for a router table from a source we were willing to cite — which is why there is no row for one in our CFM chart. The duct-diameter figures quoted above are arithmetic from published transport velocities and are shown as such on that page. Everything else here is a description of how the airflow and the machine behave.
