dust port location in miter saw hood?

[James Baker SD]

I just about have my cyclone ducting all installed and have one branch headed toward my miter saw. Currently the miter saw just sits on a long table (8' to the left, 3' to the right). Its only dust collection is the built in shop vac port. As it still scatters quite a bit of large dust (and probably fine dust as well) I plan to build some kind of shelter around the saw and attach it to the cyclone branch. Since the shelter is not built (or even designed) yet, I am free to put the connection to the cyclone almost anywhere. A downdraft style port beneath the saw is probably the only option I cannot use as the long table is supported by 5 steel storage cabinets and there is no space beneath the saw. Saw has stationary rails pointing forward so I can get fairly close to the back of the saw.

Among the options I see:
1. port above and slightly behind the saw.
2. port behind the saw at table height.
3. single port on right side (closest to the cyclone branch).
4. dual ports on each side near table height, somewhat behind saw (more work and expense splitting the branch).

Any particular feeling on which would do the best job of catching the dust? Maybe something else completely? Thanks.

James

[Tom Willoughby]

Hi James,

I have almost the same set up as you with the miter saw on my work bench with an offset to the right with approximately 3 feet to the right and approximately 9 feet to the left. I brought the dust collection in from above the miter saw and connected it to a box that sits over the saw. The box has a slot (dimensioned for the correct volume of air) that goes along the back of the box and sucks from the bottom back of the box, which draws air from the front of the saw to the back of the box. This set up is surprisingly effective. Below is a crude drawing of the dust collection box as seen from the side view (obviously not drawn to scale):

Dust collection in
___________l. l
l .................. l________
l. ____________________l
l. l
l. l
l. l
l. l
l. l Miter saw sits here
l. l
l..........................

[Tom Willoughby]

image.jpg
Hi James,

I tried to upload a photo from my phone but I still have some learning to do.

Tom

[James Baker SD]

Hi Tom:

Thanks for the photo, it makes it clearer. What size is the flex connected to the box? What fitting did you use to connect the flex to the box? If I understand, the back wall and top are double walls with an air space between that is fed by the inner back wall being shorter than the outer back wall leaving a gap at the bottom?

James

[Tom Willoughby]

I plumbed my shop with 6 inch pvc sewage pipe and then used 6 inch flex to connect to the tools. I used the bell ends of the sewage pipe that were cut off as connectors. I'll try and post a picture so that it makes more sense.

Your description about the double walls are correct.

Tom

[Tom Willoughby]

Here is a close up of the bell mouth and standard 6 inch pipe connection on top of the miter dust collection box. image.jpgKind regards,Tom

[James Baker SD]

shameless bump hoping to get some alternate suggestions as well. Thanks to Tom for all his time responding.

James

[Michael W. Clark]

James,
When I first read your post, I was thinking the same concept as Tom has. There are essentially two back walls, the exhaust air and dust flows between them, this is the plenum. The slot at the bottom is to exhaust the air at the best point behind the saw. This arrangement will take a lot of static pressure. If you have a large enough system, 3HP+, you may be OK. However, it will take a lot of flow as well.

I was able to build mine and connect in the bottom and create a trough. The dust is basically thrown into the trough and carried away, gravity is your frend. I have a 4" duct that is very close to a 1.5HP bag unit. It works much better than a shop-vac but is still not enough flow, so I am going to upgrade it to a 5" or 6" duct at some point. If you wanted a bottom connection, you can run the duct inside the hood to the bottom. With a top connection, you are going to have material in the bottom of the hood unless you have a much larger collector.

[Alan Melbourne]

i have a dewalt 718
worst dc imaginable. dc port is so small and badly designed it couldnt work. maybe 1% of the dust is extracted at best.
i dont think a huracain behind that dc port would make it better
i have a box like toms. i put 2 4" hoses to it and it woulnt work.
i bought a better extracter(5000m3 an hour.) . i have a thien baffle and the chop saw maybe 3 feet beside that.
i put a 6" hose the the bottom of where the saw sits and a flat piece above the hole to creat a slot to try and get some air circulation going.
nothing

i clamped the 6"hose to the fence right beside the blade. that half worked
it is the design of the saw. all the dust hits the support for the sliding rails and bonces everywhere.

some saws just cant be extracted from.
im thinking of getting a radial arm saw for the shop.

what kind of saw is it. is there a decent dc port on it.

[James Baker SD]

Alan, Its a Kapex and I used to think the collection was OK, far from 100%, but OK. Recently it seems to be scattering more large visible particles. Maybe the shop vac bag is full--thought I changed it recently.

A box like Tom's even without a dust collection port would certainly help contain the area littered by the saw, it would protect the areas to the side and behind (which is storage junk and hard to reach to clean). I'm not sure how the saw manages to send dust sideways, guess it is bouncing off of other surfaces with enough speed to ricochet quite a distance.

Michael, my DC is an Oneida 2000. 7" metal ducting with as few bends as I could engineer (which really isn't few, but at least they are large radius). Right now I just have a 7" elbow terminating the branch a about 3.5 feet from the saw. It is shut off with a blast gate till I figure out what to do. Every other branch also has blast gates, so I could give the entire CFM of the Oneida to the miter saw if necessary.

James

[Clint Olver]

Here are some pics of mine. It works very well. Similar to ones suggested already. Hope the pics help.

C

[Alan Melbourne]

how do you find the scroud working.
is that the dw717 (718 without the shadow laser thingy)

i like your wings.

[Michael W. Clark]

Michael, my DC is an Oneida 2000. 7" metal ducting with as few bends as I could engineer (which really isn't few, but at least they are large radius). Right now I just have a 7" elbow terminating the branch a about 3.5 feet from the saw. It is shut off with a blast gate till I figure out what to do. Every other branch also has blast gates, so I could give the entire CFM of the Oneida to the miter saw if necessary.

James

If it is throwing it sideways and all over, it will be tough. I would direct all the flow from your DC to this hood, especially when you have a lot of parts to cut. Build the surrounding hood plenty large, so the dust particles are thrown into it. I know this sounds like the opposite of the previous sentence, but if you can limit the open area on the front of the hood, that will help too. Think of your hood like a sink, if you can trap the particles in it, you probably have enough flow to take away the airborne dust.

[Alan Melbourne]

if its a kapex . make sure the vac is empty and filters clean etc.
are you useing the 36mm hose or the 27mm hose. the 36mm makes a massive diference.

[James Baker SD]

Alan,

I am using a 36mm hose. shop vac sits between 2 of the steel cabinets (about 4' clearance on each side) under the 8' long table. Recently some "stuff" got placed both behind the cabinets, in front of the cabinets and a systainer on top of the vac. Maybe I am restricting the vac's exhaust air flow too much and reducing its suction? It is not tightly blocked off, but certainly not as open as it used to be.

James