Our 30″ x 50″ plasma table has a narrow slot running down the center of the lower catch plate. If you have one of our older tables, it looks like a straight slot.
In our very recent models, we’ve changed the slot to accommodate dropping through the vent adapter. It has a circular widening in the center, which is actually to accommodate the Home Depot adapter.
The purpose of that slot is to let you sweep slag and small cutoffs through it so they fall somewhere convenient for you to clean up. But the slot was also intended to serve as a downdraft extraction port with the right flange adapter.
This post describes a conversion that turns that slot into a functional downdraft table using a laser-cut adapter plate and off-the-shelf HVAC and dust-collection parts. A DXF and a drawing of the adapter plate are attached at the bottom of the post for anyone who wants to cut their own.
For those who purchased our table prior to the slot modification, no worries! You can modify the slot to match the new design and follow the same process.
What the adapter does
The conversion is as simple as dropping the HVAC adapter through the slot in the base of the table, and then placing the adapter plate over it and using some self tapping screws to bolt it down.
It’s hard to find one of these ducts with a 4″ circular oulet, so we’ve used the 6″ variant. The round collar becomes the takeoff point for flexible ducting to a blower.
Parts list
Adapter plate: $79 from TMW, or cut your own from the attached DXF below. Material is 10 gauge mild steel in the production part. Any sheet material should do the job, since it’s a non-structural component.
Register box, 8″ x 4″ with 6″ (or 4″) round collar. Any standard Master Flow or equivalent box fits. If you’re able to find one with a 4″ collar you won’t need a step down adapter to connect the fan.
- Home Depot: Master Flow RBF8X4X6
- Menards: 4″ x 8″ x 4″ Register Pan Duct Fitting
6″ to 4″ reducer (only needed with the 6″ collar box).
- Home Depot: Master Flow 26R6X4
- Amazon: HVAC OV 6″-to-4″ Round Reducer
4″ flex hose. Dust-collection grade, not the thin aluminum dryer-vent variety, which collapses under suction. 5 ft is enough for a blower sitting under or next to the table.
- Home Depot: POWERTEC 4″ x 10 ft
- Amazon: 4″ Dust Collection Flex Hose
Blower. A small single-stage wood-dust collector in the 1 HP / 500 to 700 CFM range with a 4″ inlet. The one in the photos is the Amazon unit linked below. And we drilled holes and bolted it directly to the optional lower shelf on our unit.
- Amazon: WEN 1 HP dust collector blower
- Home Depot: 1 HP dust collectors
Total parts cost outside the adapter plate runs roughly $200.
Limitations worth knowing
A wood-dust blower pulls plenty of volume for the smoke and particulate a plasma cut produces, but its filter media (if it has one) isn’t rated for fine metal fume. The practical options are:
- Vent the blower exhaust outside the building. Simplest and most effective.
- Run the exhaust through an inline welding-grade smoke filter if venting outside isn’t possible.
- Accept that indoor exhaust with a standard dust-collector bag is imperfect filtration and ventilate the shop accordingly.
Cut your own
The adapter plate isn’t complicated. DXF and PDF drawing are attached at the bottom of this post. Material is 11 gauge mild steel in the TMW production version. If you have a plasma table, you already have everything you need to cut one.
We’ll sell you the finished plate at $79 if you’d rather skip the fabrication step.
Files
- Adapter plate DXF — for CAM / laser / plasma
- Adapter plate PDF drawing — dimensions, hole pattern, material spec
