What Size Dust Extractor Do I Need ?

I have a largely human powered hand tool woodwork shop for myself. My only concession to large electron driven woodwork machinery is a Carbatec 14 inch bandsaw (CTJ-3501). Due to space and noise constraints, I won't be adding any other big machinery (e.g. no planners, thicknessers, or table saws. Maybe a router table one day - maybe....)

How do I work out what size Dust Extractor I need ? Is there a 'rule of thumb' of some sort, or a 'workshop handbook', that specifies these sorts of things? The CTJ-3501 owners manual is quiet on the issue. I won't be using a cyclone, as the dust extractor will be located in a garden shed just outside the workshop, with a 100mm ducting run of about 9 metres.

Thanks,

AussieRoy

The 'rule of thumb' for safe dust collection from a WW machine is that the dust extractor be able to collect 1000 Cubic Feet per Minute (CFM) right at the source of the dust making.

The smallest powered dust collector that will collect 1000 CFM is a 3HP dust extractor using 6" or bigger ducting.
Use of long lengths of 4" ducting (such as a 9" run) is the surest way to throttle a dust extractor in its operation.

Another problem is that practically no machine has 6" ports and most band saws only 4" ports.
4" ducting can at best draw 400 CFM so that means you will need 3 x 4" ducts to collect 1000 CFM in the vicinity of the BS.

Typically on a BS one 4" duct should be connected to the cabinet, one directly jammed in under the table and one can go above the table.

The other biggie to be aware of is virtually all manufacturer flow specifications are about two times larger than they are in practice

Totally unsatisfactory ? - you bet - its a real mess out there in dust collection land.

Everything less than the above is a compromise which only you can decide on.

BobL is our resident dust extraction guru. His advice is sound.

Here is a pic of my bandsaw which I rigged up as per BobL's advice. Dust extraction works very well.
Attachment 283707

Originally, I had a single 4" line hooked up to the bandsaw ... and got very poor dust extraction.

Quote:

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Originally Posted by John Samuel

BobL is our resident dust extraction guru. His advice is sound.

Here is a pic of my bandsaw which I rigged up as per BobL's advice. Dust extraction works very well.
Attachment 283707

Originally, I had a single 4" line hooked up to the bandsaw ... and got very poor dust extraction.

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Ah! THERES the bandsaw. At first I thought it was a picture of a plumbing accident.

Good stuff though, mines the same saw, gives me a good idea of what to do.

Quote:

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Originally Posted by Evanism

Ah! THERES the bandsaw. At first I thought it was a picture of a plumbing accident.

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I laughed 'till I cried.

Perverted plumbing it my be, but it is no accident. What appears to be a tangle of plastic pipe accidentally assembled by a cyclone is actually a carefully crafted engineering marvel ... well ... at any rate ... it works.

Quote:

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Originally Posted by John Samuel

I laughed 'till I cried.

Perverted plumbing it my be, but it is no accident. What appears to be a tangle of plastic pipe accidentally assembled by a cyclone is actually a carefully crafted engineering marvel ... well ... at any rate ... it works.

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There is a scene in Alien 2 where some jarheads are bashing their way into a reactor. They are going into a horrible tunnel filled with secreted piping and goop....one says "yeah, but secreted by WHAT?"... It looks spooky.

I'd be keen to see how you grab the dust from just under the table. Your marvel gave me an idea On how to improve my crappy solution (I have a small piece of cardboard over the bearings and just jam the pipe in until it sticks)... But I thought it would be cool to custom make a section of 50mm or so pipe that slides past the bearings and blades that is appropriately sectioned to make all that under table bearings et al to sit in a mini wind tunnel.

I like the hulking great pipe stuck to the back! That's cool. I'm going to copy that too :)

Quote:

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Originally Posted by Evanism

There is a scene in Alien 2 where some jarheads are bashing their way into a reactor. They are going into a horrible tunnel filled with secreted piping and goop....one says "yeah, but secreted by WHAT?"... It looks spooky.

I'd be keen to see how you grab the dust from just under the table. Your marvel gave me an idea On how to improve my crappy solution (I have a small piece of cardboard over the bearings and just jam the pipe in until it sticks)... But I thought it would be cool to custom make a section of 50mm or so pipe that slides past the bearings and blades that is appropriately sectioned to make all that under table bearings et al to sit in a mini wind tunnel.

I like the hulking great pipe stuck to the back! That's cool. I'm going to copy that too :)

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The great hulking pipe is a 150 mm pipe that connects to the ductwork. There is a 100 mm hole in the cabinet through which air is drawn, and there are two 90 mm pipes coming off the big pipe, as you saw in the pic. Here is a shot of the pipe that draws air from under the table.
Attachment 283813

The ideal is as you suggested ... a pipe enclosing the blade and bearings that draws air over them and away ... but there is so little room under my table the pipe would be so small as to make it useless in a high volume, low velocity DC system. So, I cut a 90 degree angle on a 45 degree bend, as seen in the pic, and did my best to get good airflow over the blade and bearings under the table. Crude, but it works. This area now stays clean and the dust collection on the band saw is wonderful. In fact, my tests indicate that more dust is collected from there than anywhere else because the system grabs most of it before it gets into the cabinet. The fact that, unlike a table saw, the dust velocity is low, helps a lot.