Dust Collection on Table Saw Router Table Extension
Hi: I'm new here today. In fact, I initially accidentally put this question up on the Introduction forum, so I decided to copy and paste it here.
The question pertains directly to my router table, but it is more directly tied to issues of dust collection, and I recognize it's come out a bit long in writing, so you might consider paying more attention if you are knowledgeable in regard to both routers and dust collection.
I have a Grizzly 5 HP, 10-inch table saw with a router table extension. I have a 3 hp Ryobi router mounted to the router table extension. To this point in time I have used it either to route grooves at some distance from the fence or to make cuts using a bearing-guided router bit, so I've gotten away with using the table saw's fence for the work, but I need to optimize the utility of this router table.
I have several different ideas regarding means to improve the set-up, but one thing I need to make to optimize use of the router table is my focus here. Of course, a lot of the sawdust created by the router falls through the opening in the table and gets strewn all over the room from underneath the table by the spinning router bit, since this is not an enclosed router table system. To deal with that, I plan on making a polycarbonate box to mount to the underside of the table surrounding the router. It will have a hinged door to permit router bit changes and depth adjustment and a 4" dust collector mount on the back side, facing toward my dust collector.
My understanding is that the efficiency of dust collection is largely tied to the available airflow in line with the suction created by the collector. If there is inadequate airflow, the dust promptly falls out of the air in the collector ducts and never gets to the collector. Of course the opening in the router table alone will allow little, if at times any, airflow from above, so I presume I will need to cut some sort of port in the polycarbonate box itself to augment the available airflow to the collector.
Presuming that I am correct in that regard, I have 3 questions. First, what surface area should that port have? Should it be the same surface area as the cross-section of the collector duct or should it be somewhat smaller or larger?
Second, does the shape of the opening matter? I could simply drill a round hole using a hole saw or I could route a series of parallel slots, I imagine.
Third, if I get the size of the port right, do I need to screen it to keep dust from flying out through it, or should the air flow to the dust collector be great enough to keep dust from being thrown out through that port by the router?
Thanks in advance for any attention and consideration.