Check my math please (Dust Collection)

LB75

Moderator
George
So I completed the install of my new ClearVue CV1800 and am now tweaking my drops to get the 6" piping run all the way to the machines. I'm at the point now of connecting the table saw. I currently have a 4" port in the cabinet and a 2.5" shark guard port above the blade. I've been studying Bill Pentz's recommendations at the link below and in the example he cited, he went with a 4" shark guard and 5" port in the cabinet which resulted in a combined total of 32.20 square inches of cross sectional area in the ports. That's 4 square inches larger than the area of the 6" main pipe. So, my assumptions are below, hoping to get some confirmation that I'm correct before I go any further.

Dust Collection Research - Ducting

1. It's better to oversize the ports than undersize them.
2. Based on assumption 1, if I want to use the existing 2.5" shark guard port which results in a 4.9 square inch area, I should increase the size of the port in the cabinet to 6". This would give me a total of 33.17 square inches which is a better option than going with a 5" cabinet port which would result in 24.53 square inches making the area smaller than the main pipe. Am I thinking correctly on this?
3. If assumption 2 is correct, the 6" port in the cabinet would allow max air flow when I'm not using the shark guard during dado cuts and the extra 5 square inches added when using the guard won't have a noticeable impact on the system. I mean it's really only 1 square inch bigger than Bill's recommendation of using a 5" and 4" (32.20 square inches) and I can't imagine that 1 extra square inch is going to matter. Correct?
 

Bas

Recovering tool addict
Bas
Corporate Member
Your math is fine, although I think you're overthinking it.

In general, having ports that are a little bigger than the size of the pipe doesn't mean very much in terms of air flow/ "suction". Far more important is how the dust is contained/ channeled at the source.

If you have an existing shark guard with a 2.5" port, then stick with that. The shark guard dust collection on top will probably far outperform any dust collection around/ below the saw blade (at least on my saw...), so oversizing the cabinet port for a little extra air flow is not a bad idea. I have a shark guard with a 4" port, but I actually keep the blast gate for it slightly closed so it doesn't lift up the guard :) I share that hose with the 4" dust port on my router fence, and when I use that I open the gate all the way.

Bottom line, the extra square inch is not going to matter. I frequently forget to close a blast gate and the dust collection is generally fine anyway.
 

LB75

Moderator
George
Your math is fine, although I think you're overthinking it.

In general, having ports that are a little bigger than the size of the pipe doesn't mean very much in terms of air flow/ "suction". Far more important is how the dust is contained/ channeled at the source.

If you have an existing shark guard with a 2.5" port, then stick with that. The shark guard dust collection on top will probably far outperform any dust collection around/ below the saw blade (at least on my saw...), so oversizing the cabinet port for a little extra air flow is not a bad idea. I have a shark guard with a 4" port, but I actually keep the blast gate for it slightly closed so it doesn't lift up the guard :) I share that hose with the 4" dust port on my router fence, and when I use that I open the gate all the way.

Bottom line, the extra square inch is not going to matter. I frequently forget to close a blast gate and the dust collection is generally fine anyway.

Thanks Bas. I have no doubt I'm overthinking it, I'm pretty good at that :p. Just happy to hear that I did have it straight in my head.
 

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