Shop-built Downdraft Table         

My version of a combined downdraft and table saw outfeed table. This outfeed table also serves 
as a whole shop air filter when it is run periodically during the day where significant airborne dust 
has accumulated in the shop. I also decided to build it as an integral part of the table saw including 
dual miter gauge slots and an opening for a blade guard. I incorporated a 6 in. extension onto 
the downdraft table to enable this. The extension is attached to the downdraft table with 
4 in. angle brackets spaced evenly along its' length with sufficient clearance for the 
blade guard pivoting shaft.

I can also move the table away for table saw maintenance, and the weight of the downdraft table 
keeps it solidly in place with outboard adjustable leveling feet all around. The heavy-duty handle 
at the front enables me to grip the table to move it forward or sideways for any require maintenance.

When the leveling feet are raised at the table saw end, there are 3 attached casters. 
These casters enable me to roll the downdraft table away from the table saw.

The top is a grid of 1 in. holes spaced 2 in. center to center. Drilling these holes can take
upwards of 2-3 hours or so. You can make a small jig or template with the preferred hole
spacing with a 1 in. dowel attached, this keeps the holes straight and accurate.
The tabletop itself is a particulate board with melamine surfaces on either side.
Holes were drilled using a 1 in. forstner bit. The diameter of the holes and spacing were
selected with respect to both the size of the top and the need to maintain sufficient
airflow into the blower and filter system.  For example, if sanding a large piece which
blocks an area of holes, the remaining exposed holes can easily compensate airflow.
The underside of the drilled top has 3/4 X 1.5 inch hardwood lengths of board on
edge screwed to the top, reinforcing the top and making it much more rigid. I currently
have three of these lengths running in different directions, perpendicular to each other.

The downdraft table is composed of a frame of 1 X 2 members and plywood skins all around. 
The interior is composed of 2 sections; the blower section and a similar empty cavity on the 
table saw side. Both these sections have sloping plywood tops, which direct any dust into the 
dust pit at the middle of the unit.  Heavier particulate falls to the bottom of the dust pit whereas
finer dust is directed to the pleated filter assembly. The section with the blower has an additional 
frame to hold two separate pairs of pleated filters. The pleated filter pairs are easily removable
for cleaning,  and the bottom of the dust pit can easily be vacuumed out with the top removed.
My criteria for this downdraft table and combined outfeed table were that the unit be at my 
table saw height and of sufficient width and length to adequately perform as an outfeed table 
without taking too much space up. I also used typical outfeed table dimensions to determine 
the length and width of this unit.

The approximate dimensions for this downdraft table are as follows:

This portion of the downdraft table is also sealed with silicon caulk and I also went over any
seams with a flashlight to ensure there is no air entering aside from through the 4 filters
in the dust pit area. For annual maintenance and checkup, I remove one of the top manifold 
plates by breaking the caulk seal and lubricate the motor bearings, check the tension on 
the drive belt, and verify pulley screws, and belt tension.

Below, a side view of the combined outfeed and downdraft table. Notice the extension
between the downdraft table and the back of the table saw. This serves both to permit
clearance for the factory blade guard and to extend the depth of the outfeed table for
the miter jig bars. If, in the future, the outfeed table is no longer necessary, this
extension can be unscrewed and the downdraft table can be used on its own in another
part of the shop. A molding has also been applied to the upper edges of the downdraft table
to protect the plywood edges of the table.

The filters are arranged vertically in pairs. The filters are all pleated filters. I have had success
with this type of filter in a ceiling mounted air cleaner I built a few years ago, and their price is
reasonable at approx. $5.00CDN per filter. There is a short piece of wood and rubber band
assembly which keeps tension on the filters and serves to keep them tightly against the
blower housing portion of the downdraft table.
It is very simple to clean the filters and dust pit with a vacuum. The top is removed,
the inside is vacuumed, and the filters are then removed and vacuumed individually.

In my tests, it is sufficient to vacuum the inside of the downdraft table with the filters in place
every few days or so. A thorough vacuuming of the dust pit with filter removal is probably due
on a weekly basis, depending on the amount of sanding you perform, and the amount of
airborne dust in your shop.

The electrical system for the downdraft table is composed of a 60-minute timer and a 
120v dual receptacle on the either side of the downdraft table. The timer is wired to the 
motor and the receptacle is wired directly to a 120v feed into the unit. The 60-minute timer 
allows me to run the downdraft table for a period of time after I exit the shop or for a 
few minutes after a dusty operation in the shop. This is the whole shop air filter component 
of the unit. The dual 120V receptacle allows me to plug in a small hand-held sander for 
sanding work at the downdraft table itself.

Additional views of the downdraft table below:

Above, photo of the 60 minute mechanical timer. This timer allows me to leave 
the downdraft table running for a few minutes unattended to remove any airborne 
dust from the shop.

Above, photo of the dual receptacle for hand-held sanding tools along with
a close-up of the extension for the table saw blade guard.

Above, photo of dust pit and pleated filter assemblies with filter frames.

Above, another view of the sloping components and the dust pit. The filter
frames are designed to have the filters very easily removed for cleaning
or replacement. Additional peripheral support for the top can also be seen.
The underside of the drilled top has 3/4 X 1.5 inch hardwood lengths of board on
edge screwed to the top, reinforcing the top and making it much more rigid.
I currently have three of these lengths running in different directions, perpendicular
to each other.

Above, the filter frame assemblies. The filters are self- sealing to the edges 
of the frame opening when blower suction is applied.

Above, the adjustable outboard feet which lock the table at a fixed position.
These feet are easily backed off to move the downdraft table for maintenance
or to another part of the shop. The other support are casters.

I no longer use the factory blade guard on my table saw, but rather use a overhead
blade guard unit and detachable splitter. I can, at this time, remove the 6 in. extension 
and butt the downdraft table directly to the table saw, but I like the additional 6 inches 
of length the extension provides.