Dust Collection Port Sizes

Article - November 6, 2007

This week’s question comes from Rich. He writes:

Firstly, thank you for all the time and effort you put into producing such a wonderful Website. My question is this: In one of your video segments you mentioned that increasing the dust collection port diameter of the table saw to 6 inches probably decreased dust collection efficiency. I would like to know more about your experience in that area. I am in the process of redesigning my own dust collection system and, after reading about the hazards of wood dust, really want to do it right this time. What would you do differently if you had to design your dust collection system over again? What specifically is unsatisfactory about the 6 inch port on the table saw and do you also use an overhead saw guard with integral dust collection? Once again, many thanks for your time and contributions to the woodworking community. Keep up the good work. Live long and prosper!

And here was my reply:
Hey Rich. Thanks for checking out the podcast. The dust collection port on my tablesaw was originally 5″. In an attempt to increase airflow, I modified the port to make it 6″, so that it would match the size of the main trunk of my dust collection system. Afterward, I added the overhead guard with dust collection, which has a 3″ port. So between the overhead port and the cabinet port, its actually way too much surface area. In general, when you split off the main line, its a good rule of thumb to keep the sum of the two new lines no greater than the main line itself (within reason, of course). So I would have been better off leaving the saw alone at 5″. I still would have exceeded the total of 6″ when I added the dust collection from above the blade, but I wouldn’t have had to modify my saw’s port and the dust collection most likely would have been better. Lesson learned, I suppose.

I have some new equipment in the shop now and I am having a hard time deciding how to modify and lay out the new lines. As it exists, I feel like I have a big collection of branches as opposed to one main line. And I think my dust collection is suffering as a result. So I might do a little modification soon, but I’m not sure what the plan is just yet. The best advice I can give you is to put it all on paper first. Make sure it makes sense and let a few friends look at it. Peer review is a good thing! Then once you are comfortable with the layout, go for it. Good luck with your woodworking Rich. And a heartfelt “live long and prosper” to you too!

***Special Correction*** From Tom Cissell- “The area of a circle is PI times the radius squared with PI being = to approximately 3.14. So, you would have been fine with a 5 inch main port on your TS and a supplemental guard port of 3 inch because the sum of both those areas would be less then the 6 inch main.”
See Tom’s full post in the comments section. And get your calculators out if you want to get the exact figures!


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