Both my table saw cabinet and jointer "cabinet" have lots of gaps allowing
air flow from dust collector. Is this by design? For instance, the saw's
motor-access door has a 6" X 10" square hole in the top where it mates with
the cabinet when the access door is closed. Wouldn't this decrease the
efficiency of the dust collector (1.5 hp Delta dust collector). The Delta
jointer is even worse. Should I try to close up these holes?
If you were to seal all the holes so no air gets in, the DC won't work. The
dust collector does not suck dust, it sucks air and carries the dust with
it. Perhaps someone will post the perfect method for your tools, but if not,
experiment a bit. Leave enough air gaps to at least equal the exit port.
The opening would ideally be opposite the cutting blade so the air passes
the chips as they are made and carries them along with it.
Just having a ton of SUCTION in the tablesaw is NOT going to move any
sawdust/waste. So you need air MOVING thru the saw, and especially if
using zero clearane inserts you need some other way for air to get
into the saw.
Bottom line, that hole is probably NOT reducing the ability of the vac
to get the sawdust out of the bottom of the saw. If you want it to
also get dust from around the blade, etc, then you may want to use a
dust collection system attached to the bladeguard as well as dc
connected to the main port of the saw
You will get better dust collection closing off the holes. I made
hardboard covers with foam glued on one side, a wooden handle on the
other, that closes off the curved slots in my PM66. If I tilt the
blade from 90 degrees, these fall on to the floor but most of time I'm
sawing at 90.
=============================I have read all the replies to date and yours is the only one that
states that "you" get better dust collection closing off the holes...
From my experience, with my Cabinet saw (using duct tape etc
to experiment with) I have to agree with the others..... sealing off
the gaps etc greatly reduced the effectiveness of my DC ...that is not
to say that I did not seal any of the gaps..
I'm ashamed to admit that I once tried to sell vacuum cleaners. I failed
miserably at it, but one thing I did learn was that even with the greatest
vacuum power, it's still necessary to have adequate air flow for it to work
properly. The difficult part is to find the optimum level between too little
and too much air flow.
I agree with Bob, in that one cannot completely close off all the
holes, and the more holes that are closed off, the faster the airflow
will be where it counts: at the blade (You'll always have a hole
Now, doing this MAY create a small pile inside the cabinet because the
amount of air that is moving, but at that point, who cares? The goal
is to reduce airborn dust particles.
I have a Delta contractors saw and a Harbor Freight $159 dust collector. I
have run with the back of the saw covered and uncovered and see no
difference in dust collecting, so I leave it open. You do need some openings
to keep the air moving through the saw.
Bill Pentz has some design drawings on his website for dust collection
hoods for various power tools. As I recall, the gap called for in these
designs for the jointer & tablesaw is 1/2 inch. Bill's website may be
my theoretical approach would say leave about as much area in gaps as
you have in port size
if you have a 6" port, then that is pi*r^2 or 3.14 * 3^2 = 28ish sq
So leave about 28 sq inches of "gaps" elsewhere.. probably near the
top side of the table (around the gaps where the cast top meets the
metal box) such that the airflow is down and into the port. Seems
reasonable that you would want the gaps located such that the air
flowing through the gaps pulls the dust towards the port.
If you leave less area than that, you are going to create a vacuum and
it's not really going to help move dust. If you leave more area than
that you have just going to reduce the airspeed and at some point
(nothing is enclosed) there would not be enough airspeed to carry the
If you have a 4" duct, that area drops to about 12 sq inches. Now you
can see why Bill Penz and others insist on 6" ports!! Makes sense to
Thanks for all the feedback. Dave's link to http://billpentz.com was
particularly interesting. The pie-r-square theory is pretty good in that it
is something you can sink your teeth into- I shall try it. All the advise
and comments were helpful. The experiments are on!
I should say that much of what I know is derived from Bill's site and
his email support of my DC efforts. One of the items that sticks in
my mind is the fact that air is not compressible under DC conditions.
Thus the pi*r*sqr theory of mine applies I believe.
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