Thread: Overhead dust control - am I going crazy?

This is my guess as to what is happening.

A moving TS blade pushes high air speed air down and away from the table top.
When you use your overhead dust collection some of that "blade air" is sucked away from the blade allowing visible dust to deposit onto the TS top.
When you don't use the dust collection the blade air simply blows the dust away.
It all happens so quickly you won't ever see it.

However I would not be worried by any dust you can see - worry more about what you cannot see.
I wouldn't expect too much fine dust dust from your overhead dust collector as that hose is just too small but it would be better for you than nothing.
The dust devil in your shed is that your DC is inside the shed and your redeemer is that you spend most of your time using well sharpened hand tools

I absolutely love my overhead dust extraction point!

Before i got around making one, i had 2x4" ports attached to the cabinet (one at the stock point down below and the other cut into the cabinet directly behind the blade. After every session, I would be covered in saw dust, and you could see a fine spray of dust coming off the blade not to mention the cloud of dust that would be hovering around the shed when the afternoon sun hit it.

Ever since I installed the overhead extraction point, I wouldn't say no more dust but the amount of dust I'm wearing has significantly reduced and no longer notice the cloud of fine dust floating around (unless I've been doing something not attached to DC).

Hi Derek, welcome to the world of torment that is dust collection on a panel saw. I think BobL is right, with a 12" blade running at 4800rpm, your blade tip speed is about 75m/s. It's likely that the CT26 on the overhead guard is just slowing some of the air enough to leave evidence behind. By the time you count up the losses from that length of Flexi, the preseparator and a dirty HEPA filter, you won't have the airflow needed to pull enough through the overhead guard to stop that.

On my Minimax, SCM specify you need a minimum 170cfm on the overhead guard and 750cfm on the 120mm connector to the under table shroud, with a minimum velocity of 20m/s. I imagine the spec for the Hammer would be similar. In practice, the 120mm port allows about 500-550cfm at that velocity. The supplied overhead guards don't provide enough airflow into the guard to match the minimum requirement either. The Hammer one is better than the Boteco guard that comes with Minimax, but they're designed to protect fingers not lungs.

dont forget the role the saw blade plays, deep gullet blades with more tooth rake tend to carry more swarf back above the table. I'm mostly cutting melamine with high tooth count blades with minimal rake, and I'm always surprised by the change in dust level when I switch to a rip blade.