Thread: Bandsaw Dust Extraction: Modification

My first thought is when you want to open the door you have to first deal with the hose, I'd find that a bit annoying, I'd be looking at making the transition (shroud) a separate piece which is a semi permanent fix to the base but separate to the door, something like I have done here
door open 2.jpgdoor part.jpgdoor open.jpgunder table door closed.jpg
Most of the shroud stays bolted to the bracket, there is a small portion that attaches to the door which when closed completes the shroud, the original door closed upto the where the blade enters the lower cabinet and thus was only a small area for airflow, before this mod sawdust would completely surround the btm guides. I have not had to clean any sawdust from here since.
Ideally you want to pick up incoming airflow in the same direction as the sawdust is already travelling and close to where it is generated, my shroud picks up air from behind the guides, thru the table hole and from a gap of about an inch between the table and shroud, you might have to consider a movable part if you tilt your table, a panel that attaches with magnets or such.

I havent done any additional sealing of the door.

I take it that you are not going to use the lower takeoff, if so I'd be leaning towards blocking it off, my thinking being any air that if coming in this way is travelling against the direction of wind generated by the blade, it really depends on wether there is enough airflow getting into the proposed mod.

Hope this helps.




Pete

I wouldn't put all of the 150mm suck to the underside of the table as dust will escape into the shed from the saw at the top of the table. With a bandsaw its better to divide the suck up into two 3 + 5" suction ports, or 3 x 4" ports and have at least 1 of these collection points above the table.

Definitely do not seal the door and if you replace the metal door with an MDF one makes sure it has some big breather holes in it.

Two of the Three 4" flexies connected to my BS are loose fit connections as I also swap these over to use ton my Linisher.
On the BS, I have one flexy connected to the bottom cavity, one above the table and I jam one under the table.
I don't open the doors all that often and when I do it's easy enough to unjam the one under the table to get access and half the time it's attached to the linisher anyway.

My bandsaw had a port just like the one you envision ... but it did not work very well. A fair bit of dust escaped between the table and the lower cabinet.

aaaBack (Finished).jpg

So, I took a leaf out of BobL's book and just "clicked" the 4 inch flexy between the cabinet and the table, and that gives a better result. The original port is sealed off.

Excellent thanks guys.

You make a good point Pete about access to the lower cabinet, I'll have a play with some ideas using a separate extractor point to the door. I attach my flexi on the run though so I'd be doing this fairly regularly as it is.

I'm getting mixed messages about sealing the lower cabinet. Intuitively I agree with Pete in sealing the lower outlet, however I also recognize the need for breathing space.

I currently have my DE setup with a 6inch main with a 4inch branch (which I close off unless being used for overhead at the TS). The main feeds to the base of the BS through a 6-5inch adapter. I'd planned to run a 4inch from the top down, similar to John's setup and the 6inch to under the table.

John, interesting to hear that you get more effective extraction by jamming a pipe under the table than using the original outlet, given their proximity I'd have thought there would be minimal to no difference. Do you guys jam/click it from the side or front? I tried jamming the 6inch under the table (side) today and found the cabinet filled with more dust than if I attach it to the base outlet. This perhaps suggest I should keep the lower outlet?

Regardless of what I do under the table an overhead extraction point is on the "to do" list.

Thanks again.

Gareth

Interesting setup Pete. Is the blade brush standard or did you add it? My guides get fairly dusty whereas yours look just about dust-free. Could you perhaps post a couple photos zoomed out a little?

Thanks,

Gareth

Hi
My Leda BS has a 2 part lower door, I open the bottom one when using the BS, its much quieter and cleaner.

With the door closed, there is a "partial vacuum" inside the lower cabinet with resulting high pitched whine as the air passes through the blade gap.

I have a 2 hp dusty, 150 mm tubing, 2 !00 mm flexys to the lower cabinet.

I took BobL's advice to provide good air flow.

Cheers Barry

Gareth,

No two saws are alike, and I usually find myself fiddling a bit to get things right. I definitely get better dust extraction by clicking the 4 inch flexy between the table and the lower cabinet on the Laguna (compared to hooking it up to the side port). It comes in from the side, as per the pic. Your saw may perform differently, but when using the side port I got a fair bit of dust billowing between the table and the lower cabinet. My saw has three ducts, so the lower cabinet has a duct working along with the one clicked in between the table and the cabinet and another overhead. We should always have a duct pulling air from the lower cabinet.


I find that the overhead dust extraction works best on the old saw which is used only for cutting fairly thin material and curves. The Laguna is a re-saw and veneering saw, and I am always cutting wide material with it. This is never quite as clean as when cutting thin material, because dust gets caught in the long kerf space, where there is almost no airflow. looking at ways of improving this, but I doubt it will ever be as good as when cutting thin material. Not a big problem as the dust has very little momentum and just falls onto the table. Next trial will be to block the overhead duct when cutting wide material to see if I get better suction elsewhere.

Originally Posted by GarethR

Interesting setup Pete. Is the blade brush standard or did you add it? My guides get fairly dusty whereas yours look just about dust-free. Could you perhaps post a couple photos zoomed out a little?

Thanks,

Gareth

longer view shroud.jpglooking down hole.jpglooking up hole.jpgblade brush inside.jpgblade brush outside.jpg
A few different views, the top half of the shroud showing the funneling effect, the part that is on the door meets up with the angled piece (where the brush is). It only has three sides, open at the rear and held in place by the one bolt.

The blade brush is standard but I have also added some brushes, not really required for dry stuff but I find them necessary when cutting green stuff as the build up of gunk on the blade gives me grief, the added ones are from the surround from a vacuum floor attachment. I also added some brushes on the shroud itself, moreso to deflect any slivers that happen to fall down the hole as I don't use the plate that normally fits in there.

btm cabinet dust extraction.JPG
I also use the lower cabinet collection point, with a quick and rough addon to improve flow into this port, a lot more work should be done here re. bell mouth entry but that is for another day, BobL has posted a fair bit of info re bell mouth which is well worth incorporating into your mod if possible, Bob will also point out that any cross hair grill will restrict flow, since I took this pic I have removed the cross the caveat here tho is if you are using a DC where dust/chips impinge on your fan there is potential for larger bits to hammer the fan and cause damage, gain on one hand but lose on another!! I have a cyclone so not an issue for me.

Both these ports are the standard 4 inch, if I was to do any further mods I would stay with the four inch on the lower cabinet but with bell mouth entry, maybe a five inch to the under table also with improved entry, where I feel I would gain most is an external pickup at the rear of the table, a lot of my BS work is done using the sled which allows the dust to hit the table and consequently is swept to towards the rear and so I get dust pile up on the floor at the back of the machine, but that too is another day




Pete

Originally Posted by pjt

btm cabinet dust extraction.JPG
I also use the lower cabinet collection point, with a quick and rough addon to improve flow into this port, a lot more work should be done here re. bell mouth entry but that is for another day, BobL has posted a fair bit of info re bell mouth which is well worth incorporating into your mod if possible, Bob will also point out that any cross hair grill will restrict flow, since I took this pic I have removed the cross the caveat here tho is if you are using a DC where dust/chips impinge on your fan there is potential for larger bits to hammer the fan and cause damage, gain on one hand but lose on another!! I have a cyclone so not an issue for me.

The likely hood of any "bits" large enough to be stopped by this grill getting into this duct are quite low so this should not be a problem. The grill reduces the flow by about 20%.

Both these ports are the standard 4 inch, if I was to do any further mods I would stay with the four inch on the lower cabinet but with bell mouth entry, maybe a five inch to the under table also with improved entry, where I feel I would gain most is an external pickup at the rear of the table, a lot of my BS work is done using the sled which allows the dust to hit the table and consequently is swept to towards the rear and so I get dust pile up on the floor at the back of the machine, but that too is another day

Unfortunately these ports are not 4" but 94 mm which doesn't sound like much but these factors all add up.

Check out my approach in this thread to dealing with below table dust:

https://www.woodworkforums.com/showth...96#post1688596

Using a shop vac (higher pressure than a DC) and a narrow collection point encompassing the blade directly below the table in this way I am able to get about 99% of the dust before it enters the lower cabinet.

This frees up your DC for the above table dust.

It's hard to beat high pressure suction right at the source of the dust.

I wouldn't recommend using a VC for a bandsaw or any machine that generates air currents around the blade as these air currents enable fine dust to easily and quickly ride away into the rest of the shed far faster than a VC can suck the air in.
The other problem with VCs I will discuss below.

I have not seen a single claim made on this forum (and in most other places) regarding percentage of dust captured by DCs and VC etc able to be substantiated mainly because this requires a highly specialised and expensive setup and testing gear which is rarely undertaken. Most machinery users estimate things visually which is not an accurate method.

To start with the measurements would need to be to conducted in a dust free room.
The weight of dust produce during a cut and how tthe dust moves between various parts of the bandsaw would need to be determined.
The piece of wood to be cut and DC and VC filters would be weighed before and after the cut was made.
Then the wood cut and the weight of dust captured by the DC and VC filters weighed and compared with each other and to the weight of wood loss by the cutting.

Even after all this, this would only account for weight of sawdust but not for the numbers of particles of sawdust.
A high resolution balance will be needed to cater for the small weight fraction of the fine dust particles produced.
Remember its the small particles we need to worry about, the ones that can be seen don't do much in terms of health issues.
To properly asses the efficiency of number of particles captured a very expensive particle detector counting system would be needed.

The VC and DC might even initially capture 99% of the weight of visible sawdust but there is no way it will capture and retain 99% of the sawdust particles. Even if a shop vacs captures 100% of the dust it also minces large particles into smaller ones. which go through the filters or leaks etc. Only a few large particles need to be minced to make lots os smaller one. Some shop vacs actually make so much fine dust that they end up emitting more fine dust particles than the total number of particles (fine and coarse) that they initially captured.

Ultimately unless a VC is located outside or located inside an air tight enclosure and vented outside they will eventually fill the air in a shed with fine dust.

@BobL
ok, let me clarify my above quote - more accurately ... )

Using the dust collection pipe approach - pipe attached directly to bottom of bandsaw table, enclosing blade such that high velocity air is pulled across the gullets of the blade, virtually all visible dust that would otherwise end up in the lower cabinet of my bandsaw is eliminated.
I have an old cast iron style band saw with no dust extraction ports at all. I tested it out when I first got it and quickly filled the lower cabinet with sawdust. Rigging up this pipe under the table, and using my Festool shop vac, I get virtually no dust accumulating in the cabinet. I open it every once in a while and vacuum out the very small amount of dust that finds its way in there. I doubt I could get better below table results with my clearvue, but eventually when I get time I will cut a hole in the lower cabinet and rig up something there as well - maybe do a better job then with any invisible dust (???). For now I just have 6 inch flex (from clearvue) collecting dust from the air above the table and behind the cut. Hopefully this is pulling most of the fine dust out of the air.
I think the shop vac should be doing a pretty good job of filtering - it is rated for asbestos after all, but also I have the older model that has an outlet port that you can connect a hose to in order to vent the output air outside. I sometimes do this when cutting nasty stuff like MDF, but must admit I am usually too lazy to hook that up when I am moving the vac around the shop.
So just to reinforce, when I say I am capturing 99% of the dust under the table I mean 99% of the dust that was accumulating in the cabinet of my bandsaw is now collected before it ever reaches the cabinet.

That makes it clearer, and I understand what you mean about grabbing ithe dust as close as possible to the source. I get about the same effect with a 4" flexy connected to a 3 HP jammed under the table. The advantage of the extra air flow (about 3 times that a VC can pull) is that it will also grab more fine dust. Fine dust collection from a BS is tricky, about the best one can do is have as much air flow going as near as possible to the source.

I have one of the 14" generic bandsaws (Woodman) that does not have any dust collection ports. Dust was flying everywhere so I made up a 4" hose fitting as shown which works really well. I also have a 6" hose above the table that can be moved between the bandsaw and the top of the router table. The under table hose clears nearly all the dust that drops so that there is practically no dust collecting in the bottom of the bandsaw. The 6" above table fitting also clears practically all dust. The difference is amazing as before the modification dust was being thrown everywhere.
Bandsaw dust collection.jpg