Obviously a dust collector is better than a ShopVac, but some of us have budgets, or shops that are too small to accommodate a dust collector system. My table saw is completely enclosed (except for the tilt quadrant on the front) and the blade guard has baffles inside to force the saw dust down into the throat opening. The 2/12" vac port on the back of the locker bracket collects nearly everything the saw produces. The rest falls into the hopper shaped belly pan that has a separate vac port for clean out.
Thanks. I was just wondering if the higher velocity air generated by the shop vac would be more efficient in the small port of the above the blade collector. I don’t really understand the relationship between velocity and volume and how this affects efficiency. I installed my central duct collection using 4” piping as the intake port of the collector was approx 4” and most of my tools have 4” ports, including the cabinet portion of my table saw. I wonder if I should have gone with 6” but not sure I would have had the space.
Oh well, always something to tinker with.
On a table saw, a blade shroud under the table is the best. Older contractor saws with just an open cabinet are the worst. Why? Because the air stream is more focused on the area where the dust is generated. Once the dust start to fall to the bottom, only gravity will work to catch it. Dust has to remain in the air stream to get collected, in my experience. You need a great volume of moving air to collect it, way more than home shop dust collectors can make, also in my experience. My 1 1/2 HP jet 1100's get quite a bit of it, but the corners of the cabinet just don't get evacuated on my contractor saws. My Bosch 4100 has the blade shroud with a 2 1/2" rear port and that works really well.
I find that a drum sander or planer that throws a lot of fine dust or even larger chips is best collected by the stationary DC units. A shop vac just can't keep up, and as long as the dust stays suspended in the air stream a DC, works best. Once it starts to fall out from gravity, it's a lost cause. The closer you can confine the collection point to the generation point, the better its works, no matter which you use, a DC or a shop vac.
For example, on my older Powermatic 12" saw, Model 68, there was no blade shroud. I fabricated up some flat sheet metal and a soldered a 4" port as close to the blade as I could and what an improvement! Also, the open cabinet of the hybrid Craftsman has only a slanted shelf near the bottom port and there's just not enough volume of moving air to catch the dust. I don't know the exact CFMs on the Jet 1100's but it ain't enough for this application. Oh, it's better than none at all, but it's not great.