Quote Originally Posted by Steve Wurster View Post
The Harvey has an odd design where the 4" port drops immediately down to 3" for the pipe, then goes even further down to 2.5" just before the guard. And that port on the guard is 90 degrees to the blade, meaning there seems to be a lot of step-down and potential for losses along the way. I'm not sure how well my setup would perform given all that.
Steve, I agree with your points and that's part of my concern.

I'm currently using the original SS overarm and it works pretty well with most simple cuts. If I remove the hose from the back of the guard and make a cut with the DC off, it's pretty amazing how much dust and chips are thrown out the back of the guard. Clearly, air flow generated by the spinning blade can be harvested to help direct dust into a guard. So far, SS uses this approach on their original guard and not the new floating guard.

In my opinion, it would probably be helpful to create high velocity suction at the rear of the blade as well. I'm assuming a lot of the dust is generated as the rear of the blade is skimming through the cut (I'm talking dust here, not chips), in addition to dust/chips following the blade around from the front of the cut. A high-speed camera could provide some illumination on this issue with a few simple tests (e.g. running a board half way through the blade and seeing how much dust is following the blade around, etc…). Regardless, SS has already proven there’s value in capturing dust at the front of the blade, a point that’s slightly unintuitive.

I've toyed with the idea of designing my own dust collection guard but some research is needed first regarding the issues noted above. Specifically, what are the main sources of dust/chips…leftovers in the blade gullet, free dust in the airflow of the blade not captured by the internal DC, new dust created as the blade skims the rear of the board, etc…