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Thread: Advice on miter saw dust collection port size

  1. #1
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    Advice on miter saw dust collection port size

    I recently bought a new (and hopefully last) miter saw - the Bosch 12 inch slider. I have a 3HP cyclone DC with 6 inch pipes in my shop. I made a larger rubber shroud to replace the original and so far have only used the saw DC port connected to one of my shop vacs until I can get it permanently connected to the larger system.

    I intend to branch off and connect a smaller (probably 2 1/2 inch line) to the saw port and a larger line to a shroud that I'll be making to cover the area near the bottom of the saw. My dilemma is the size of the line going to my home made shroud. I know that a full 6 inch line will give me more CFM and a 4 inch line will give me more velocity. I'm not sure which will work better in this application and am looking for advice/comments. Sorry if this topic has been covered before; I have read a lot of threads on miter saw dust collection already.

  2. #2
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    6" or 5" would be my choice for the shroud over 4" no question. It's not about "velocity"; rather, it's about moving volume of air. My shroud has a 5" drop and I get reasonably acceptable collection...at least as much as you can actually collect from a miter saw that likes to spit debris in multiple directions.
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    The most expensive tool is the one you buy "cheaply" and often...

  3. #3
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    Are you going to connect the smaller line to a branch of the dust collector or run a little shop vac on it in addition to the shroud? I'm planning out the exact same scenario right now. I am thinking I'll do 6" on the shroud.

  4. #4
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    I originally had the small port on the back of mine connected, but now just have a 45 degree elbow on it that directs anything coming out the blade guard port into the shroud. It's much less cumbersome when I am cutting at angles and less complicated. All of the DC air flow is focused on the hood that way.
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    The most expensive tool is the one you buy "cheaply" and often...

  5. #5
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    6" on mine, and wouldn't want smaller.

  6. #6
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    Jim and Tom, thanks for your inputs and confirming my original thought that the full 6 inch line would be better. And Jim, I like your idea of just having the small saw port point in the direction of the shroud. I'll have to look at possibly redesigning the Bosch port though since it pretty much points north.

  7. #7
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    I just put a PVC 45 elbow on the end of the blade shroud port of my Delta CMS so that it wasn't pointing "up" during a cut.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  8. #8
    I've got a 4" Y with a 4 inch line to the shroud and a 2 1/2 one on my DeWalt 12" slider and it does okay. I have low expectations from this and it is by far the most inefficient setup in the shop. Perhaps I'll try it with a 6" line and see.

  9. #9
    And a related question... (I'm not sure what the etiquette is about highjacking a thread or if each question should be in a new thread...) When connecting the dust shroud to the DC, is it better to split up the 6" main and have 2 4" going above and below the shroud, or use a PVC 45 elbow as Jim was saying and just connect the 6" directly to the base of the shroud?

  10. #10
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    Are you guys attaching the 6" DC hose to the top or bottom of the shroud? Seems like the top would be better for the fine dust?

  11. #11
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    I'll post these pictures again, since they're already in the gallery here. I built this over ten years ago, as a prototype, thinking that I would make any changes needed. I've never needed to change anything, and it's still in use. It's 1" deeper, front to back, than the saw by itself.

    There is a 6" duct under a built in plenum under the back. There is a slot all along the back of the top of the plenum. No dust, even fine dust, gets back out the front. We can even use it in a finished house with no worries about dust on anything in the house.

    DC is a 3hp four bagger that rolls in, and out, of regular doorways.
    Attached Images Attached Images

  12. #12
    Thanks. But I don't understand the "slot all along the back of the top of the plenum" part. Also, would a single 6" duct be necessarily better on the bottom part? Due to my layout, it might be better to connect it on the side...

  13. #13
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    My 6" port has a large square HVAC fitting on the bottom of the shroud which has a 6" port on it. The 2" port on the saw has a vac hose long enough to travel into the sq HVAC fitting. Anything that doesn't find its way into the opening gets brushed into the sloped opening on the bottom. Dave

  14. #14
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    Jean-Claude, I think the slot along the back just makes sure there is suction all across the back of the box to cover any direction the sawdust was headed. That PVC elbow directs most of the heavy sawdust down towards the slot. I don't know if it mattered or not, but seemed like a good thing to try when I made that first "prototype". It worked so good from the start that I never had any reason to try it a different way. I can't say if it's necessary or not, but since this one works so well, if I built another one, it would be the same way.

    My duct comes in from the bottom only for the reason that my setups are always temporary (sometimes up to two years, but typically around one), so ductwork is just laying on the floor inside whatever house we're working on.

  15. #15
    6" to an HVAC register boot. I put a couple of sheetmetal wings on the boot to help capture the dust. The saw is able to swivel and tilt it's entire range with this setup. I ran 4" to a 4" x 2.5" adapter to the factory port on my Hitachi. I split the 2 from a 6" line.




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