DC CFM Observation

[Michael Sapper]

I finally got tired of the dust in my shop and purchased a JET 1100 DC. I have been experimenting with a single 4” 10ft flex house attached directly to my contractor saw vs. a second setup with the saw and my jointer, also with a 4” 10ft hose, both gates open.

Judging by the cyclone effect (the speed of the spinning saw dust) in the dust collection bag, it appears that you’re better off to have the second hose attached and open even if not using that tool. When both are open and attached the cyclone effect is noticeably faster. When just the single hose is open, it’s almost as if I’m choking off the power.

Is my observation of the airflow with the single vs. double hose attachment correct?

I plan to eventually setup a fixed system with about 18 feet of 6’’ metal duct running near the big machines with the 4” flex hose attachments.

[Art Mann]

Your observation is not correct. The only air flow that matters is between the dust collector and the machine you are running at the time. Leaving multiple gates open can only decrease the airflow in the path you are interested in.

[Jim Becker]

Your observation is not correct. The only air flow that matters is between the dust collector and the machine you are running at the time. Leaving multiple gates open can only decrease the airflow in the path you are interested in.

True. The better fix is to take off the 4" wye adapter and use a 5" or 6" hose with a reducer right at the machine port.

[Jim O'Dell]

By having both gates open, logic says you may in fact have more flow at the collector, indicated by the dust swirl in the bag. But you have less flow at the machine you are using, which is the key. Flow at the machine is the game you want to win. Jim.

[Alan Schaffter]

True. The better fix is to take off the 4" wye adapter and use a 5" or 6" hose with a reducer right at the machine port.

Yes, take the adapter off and go with larger duct (I don't remember if that blower supports 6" duct but likely does). But, you are better off not reducing at the machine. The ideal is "big as possible as far as possible" -that is, if 6" duct is ideal for your blower, then take 6" inch all the way to the machine (unless you are a long way from the blower). Your goal is to capture as much dust as possible at the source and that means sucking up the max volume of air possible. Velocity comes into play keeping the dust in the air mass as it travels in the duct.

Now, as far as a cyclone goes- restricting air flow can reduce the effectiveness of the cyclonic separation of fines, but that is with a true cyclone separator. The guys with ClearVue cyclones can actually watch this happen.

[Jim Becker]

Alan, some machines are just impractical to retrofit for a larger dust port but I agree that when you can, it's the way to go. Alternatively, reducing right at the machine, you at least get a nice venturi effect.