Shop Vac or Dust Collector

[Red2000SS]

What is best to hook up to the BT3100 dust port?

I realize that a real dust collector can move a lot more air than a shop vac, but hooking up to the small dust port on the BT3100 (2.5 inch), it seems that a shop vac would be better since most of them can pull a much higher vacuum on a such a small diameter. In other words, a shop vac can pull a lot more air through a 2.5 inch port than a real dust collector, because they can pull a higher vacuum. This would be reversed on a much larger port such as a 4 - 6 inch port - a shop vac just can't move that much air through a larger port.

Any comments?

[LCHIEN]

What is best to hook up to the BT3100 dust port?

I realize that a real dust collector can move a lot more air than a shop vac, but hooking up to the small dust port on the BT3100 (2.5 inch), it seems that a shop vac would be better since most of them can pull a much higher vacuum on a such a small diameter. In other words, a shop vac can pull a lot more air through a 2.5 inch port than a real dust collector, because they can pull a higher vacuum. This would be reversed on a much larger port such as a 4 - 6 inch port - a shop vac just can't move that much air through a larger port.

Any comments?

I don't know the actual figures, its a complex web of
head (vacuum or negative PSI) that the device can put of vs.
unrestricted airflow.
A shop vac can probably suck up 13 PSI of vacuum but can only pull 50 or 100 CFM on an open port.
A DC can pull 1000 or more CFM but can only put up about 6 PSI on a closed end pipe.
The reason is that the impellors are designed differently.
Which one works better pulling thru a 2.5" restricted port sort of depends on where the crossing point is in performance but I would bet the DC works better.

What I did was to put a 4" port on the bottom of my BT and my DC pulls on both the 2.5" port and the bottom and there is absolutely no dust left inside.
I haven't plumbed to the port on top of my shark but if i did there might be no dust left on top of the saw, either.

[Red2000SS]

I don't know the actual figures, its a complex web of
head (vacuum or negative PSI) that the device can put of vs.
unrestricted airflow.
A shop vac can probably suck up 13 PSI of vacuum but can only pull 50 or 100 CFM on an open port.
A DC can pull 1000 or more CFM but can only put up about 6 PSI on a closed end pipe.
The reason is that the impellors are designed differently.
Which one works better pulling thru a 2.5" restricted port sort of depends on where the crossing point is in performance but I would bet the DC works better.

What I did was to put a 4" port on the bottom of my BT and my DC pulls on both the 2.5" port and the bottom and there is absolutely no dust left inside.
I haven't plumbed to the port on top of my shark but if i did there might be no dust left on top of the saw, either.

I haven't actually measured what type of vacuum a shop vac or real DC can pull, but from what I have read, your vacuum numbers appear way high.

I would agree with the flow numbers - 50-100 cfm vs. 1000 or more for a DC, but the vacuum I have seen quoted for dust collectors is in the order of 10-12 inches of WATER- this is less than 1 psi of vacuum. I have seen vacuum numbers for shop vacs on the order of 100 inches of water - maybe 4 psi of vacuum.

There is no way a shop vac can pull 13psi of vacuum. A perfect vacuum is only 14.7 psi. An example of this would be using your Bt3100 on the international space station with the dust port hooked up to... SPACE - unlimited total vacuum. This would assume the space station could make up all air exhausted to space and maintain 14.7 psi (1 atmosphere) pressure - highly unlikely - you would probably die very quickly after you opened your 14.7 psi "dust port"... LOL - this is only an example... but your floor would be spotless! - no sawdust!

Not trying to be confrontational, I am really interested in the answer - my gut feeling is that a shop vac could move more air through a small (2.5") port than a real dust collector.

As you stated, there is a crossover point. I am sure a shop vac could pull more air (real cfm) through a drinking straw than a real 1000 cfm dust collector. I am also sure that a real dust collector could pull more air through a 2 ft diameter pipe. The crossover point is somewhere in between.

Your solution of having your DC pull both from underneath and from the 2.5" port seems to be the desired end result - no dust.

My question is more if you could only hook up to the 2.5" connecter, would you be better off using a shop vac or a real dust collector.

Thanks for any input.

[LCHIEN]

Yes, I stand corrected on the vacuum.
A typical DC like the HF 2HP and the Jet 1.5 HP DC1100
would pull a max of less than about 10" of water, well below a PSI.
And a shop vac was similarly overstated.

[Stytooner]

Not everything is covered in the discussion yet. On the BT's dust port, it isn't as simple as looking at the DC numbers. The BT is pretty efficient at evacuating sawdust with nothing hooked up. This comes from the blade and it's shroud actually working somewhat like a blower itself. It blows most of the sawdust out of the port. At that point, it's an easy task for either a shop vac or DC to carry the particles away. I think both would work equally well. Then you can start adding modification and those possibilities are numerous. The more modifications you do to get zero dust left in the cabinet like Loring mentioned, the more likely a DC will start to outperform the SV.

[LarryG]

What Lee said.

I started with a shop vac connected to the tailpipe of my BT3100. Now I have a 4" dust collector hose, connected via a reducer fitting. I really don't see much if any difference in the two setups for this particular tool.

The dust collector is far superior for other tools, though. There's no way a shop vac could keep up with my jointer or thickness planer ... the small-diameter hose would be prone to clogging, and I'd have to empty the tub ten times as often as I empty the DC's lower bag.

[LCHIEN]

What Lee said.

I started with a shop vac connected to the tailpipe of my BT3100. Now I have a 4" dust collector hose, connected via a reducer fitting. I really don't see much if any difference in the two setups for this particular tool.

The dust collector is far superior for other tools, though. There's no way a shop vac could keep up with my jointer or thickness planer ... the small-diameter hose would be prone to clogging, and I'd have to empty the tub ten times as often as I empty the DC's lower bag.

Don't forget the noise - I'd much rather have a DC rumbling than the SV screaming.

[LarryG]

Don't forget the noise - I'd much rather have a DC rumbling than the SV screaming.

A good point that I tend to forget, since my shop vac powers a "central" vacuum system consisting of 2" piping and blast gates, with the vac itself (and its noise) isolated in a separate room behind a closed door. Running, it's just loud enough for me to hear so I'll not forget to switch it off.

[fredg50]

I've been using my shop vac hooked up to the back of the saw and it works ok but I always seem to get a lot of dust on top of the saw. I'm using a zeo clearance insert. I hooked up my dust collector directly to the back of the saw with a 4 X 2 1/2 reducer and I don't get any more surface dust.

[Jnam]

I have both a shop vac on the back port and a 3hp Pentz cyclone hooked up to a custom hood.

The cyclone can pull more through the same dia line as the shop vac, much more. I accidently let a whole pencil roll across the top of the table saw, it wasnt rolling, it was being drawn and eventually sucked up the cyclone 2" port of the table saw hood. It had been drawn from a bout 15" away.



You can kinda see the hook up here. The blue hose is the shop vac

[cgallery]

The cyclone can pull more through the same dia line as the shop vac, much more.

Good information.

I've never owned a dust collector, just use a Shop Vac myself. No real room for a dust collector, really.

And I had always read (including at BP's site) that for smaller ports, a Shop-Vac works best (although I don't think he says what constitutes smaller).

So last year I was at the woodworking show in Milwaukee and walked by a working dust collector w/ a 4" intake sitting open and I put my hand near it and it was sucking quite a bit. Gobs of CFM.

BTW, why don't you connect the cyclone to the rear port? It seems as though it would provide plenty of power to handle both the top and front ports at the same time. And less noisy than having a separate vac running, too.

[LCHIEN]

I currently have the two 4" ports on teh DC, one side hooked to the BT3000 dust port on the blade shroud in the back and a second four inch hose going to a a 4" port mounted to a plywood board covering the bottom of my saw. This keeps the inside of the saw nearly spotless. I still get some dust sprayed over the top of the saw.

One day I think I'll split the hose going to the 4" hose going to the dust port into two 2.5" hoses going to the shark guard and the dustport.

[Knottscott]

Noise and capacity issues favor the DC, but if your stuck with a shop vac, a separator lid on a 5-7 gallon bucket can help with some of the capacity constraints.

[Jnam]

G
BTW, why don't you connect the cyclone to the rear port? It seems as though it would provide plenty of power to handle both the top and front ports at the same time. And less noisy than having a separate vac running, too.

Simply access to the rear port. I would have to pull a line down further down along the duct run. to keep the line away from the wood travel area.

I wish I could. Maybe I'll give it somethought