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Thread: Miter saw dust collection

  1. #16
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    If you split the 6" drop to two ports for the same machine, I'd do a 6/4/4, personally, to keep air flow "up".
    --

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

  2. #17
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    Quote Originally Posted by stan shields View Post
    <p>
    So I am closing in on a design concept. I will have a 6 inch duct coming from under the saw, I am considering connecting that to a wye with one leg mounted under each side of the saw just to the rear of the fence. I will install a curved back to contain the spray. What do you think will work better: a 6X6X6 wye or a 6X4X4? I guess it is a volume vs. flow rate question?</p>
    The first question is what are you using for a dust extractor?
    Chris

    Everything I like is either illegal, immoral or fattening

  3. #18
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    So, maybe velocity might be more important than volume in this case since the duct will be below the saw attempting to pull the airborne material down, I guess even two 4 inch inlets is a larger area than the single 6 inch. Think I'll try the double 4 inch and see how it goes, I can always make the openings in the bench larger if need be.

  4. #19
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    My shroud for the Glide saw is a semi circular shape that the saw sits in from the fence back. That circular shaped wall sits in a square outer box and has a gap at the lower edge and the air is drawn up through the plenum chamber that is formed between the circular wall and the box walls. This is the important bit, it is vented through the chamber from the bottom up by a Clearvue via a top mounted 150mm duct which flows over a 1000 CFM per minute and works very well. It is the massive air flow that picks up the sub micron dust that our lungs trap and do not release and which eventually causes lung issues. I will post photos later but mine both picks up the debris that comes off the saw and keeps the small invisible dust to a minimum. If you look at mitre saws the Kapex is the only one that actually extracts from the shroud, the rest eject the debris from the blade to be picked up behind the blade. The best (kapex) is less than perfect despite all the claims to the contrary and the worst is just plain damned awful and the Glide is a candidate for that prize.
    Chris

    Everything I like is either illegal, immoral or fattening

  5. #20
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    Quote Originally Posted by stan shields View Post
    So, maybe velocity might be more important than volume in this case since the duct will be below the saw attempting to pull the airborne material down, I guess even two 4 inch inlets is a larger area than the single 6 inch. Think I'll try the double 4 inch and see how it goes, I can always make the openings in the bench larger if need be.
    I did the under saw thing since about 2000 until a few weeks ago. It wasn't very effective, even with the relatively open bottom of my miter saw...hence, the hood I built and showed a photo of previously.
    --

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

  6. #21
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    it is all about the dust extractor and that is the first question I always ask because the design and results are absolutely dependent on that. Some devices people call extractors simply won't do the job, period and end of argument.
    Chris

    Everything I like is either illegal, immoral or fattening

  7. #22
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    Here is the pics of my shroud
    I can't Get it Any Closer.JPG
    IMG_1595.jpgIMG_1596.jpgIMG_1600.jpgIMG_1598.jpgTop View of Hood.jpgAir Entry at Bottom of Hood.JPG


    Blast Gate Installed in Top Plenum.JPG

    The three ducts shown was something I was contemplating but in the end I went with a single 150mm duct which seems to do the job. There is one major problem with this design as it is and that is the saw cannot be rolled to the side to do compound cuts but it would be easy enough to make the sides either hinged or removable for those if necessary. The air inlet needs to be at least twice the area of the duct for technical reasons I don't fully understand.
    Chris

    Everything I like is either illegal, immoral or fattening

  8. #23
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    Here are some more pics. I put the saw on a sliding base for a couple of reasons, it made it easier to get it as far back into the shroud as possible and it made lining up the saw to the fences easier and if I wanted to use sub fences on the saw it could easily be re-aligned to the bench fences which use Incra tracks and stops.

    Glide Saw Installed.jpgI can't Get it Any Closer.JPGSliding Base.JPGShowing Incra Fences.JPG


    I can't delete the attached thumbnail and I don't know how it got there.
    Attached Images Attached Images
    Last edited by Chris Parks; 11-05-2017 at 8:33 AM.
    Chris

    Everything I like is either illegal, immoral or fattening

  9. #24
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    I have a 1-1/2 HP 6" inlet Shop Fox:1280 CFM, 12.3 inch static pressure. There will be 6 inch PVC pipe to the wye at the miter saw, couple of 45s along the way.

  10. #25
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    Quote Originally Posted by stan shields View Post
    I have a 1-1/2 HP 6" inlet Shop Fox:1280 CFM, 12.3 inch static pressure. There will be 6 inch PVC pipe to the wye at the miter saw, couple of 45s along the way.
    If it flows more than 600cfm in a 150mm duct it will be doing well. It is impossible for 12" impeller to flow 1000CFM, every manufacturer/supplier tells lies when selling these things. A 15'' impeller only just flows more than 1000CFM in the real world.
    Chris

    Everything I like is either illegal, immoral or fattening

  11. #26
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    Stan,

    Just to add to what Chris said, the 1280cfm is impossible in the real world with your DC. Although the blower alone could get over 1000cfm, per the Cincinnati fan charts for a 12 impeller you would need a 3HP motor to be able to produce close to 1300 cfm and that is just the blower. Wood magazine just did a review of what real world flow is like with 1.5HP DCs and seasoned (used) filters both cleaned and freshly caked. Your DC was one of the best providing 400CFM through a 4" 10' flex hose. That equates to 4500FPM for you velocity (which is very good). However, when you look at the same CFM in a 6" duct your velocity is well below the desired level to avoid clogs. Will it work, sure you will feel plenty of air and you will subjectively say it has great suction. For 1.5HP DCs you are typically better off with 5" ducts to optimize velocity. That is said without knowing how long your runs are before you get to your wye and a couple of 45's mentioned above. Also, your unit with new unused filters provided just over 700CFM in a metal 6" test duct (which is just barely above minimum levels to avoid clogs).

    Bottom line, can you use 6". Sure people do it all the time. Would 5" probably be better performance? Most likely. Can you use 4", absolutely, but you are throwing away performance by doing it.

    If you add a separator to your Shop Fox that will further reduce your airflow (although it will keep your filter cleaner, longer). Without knowing more about your complete system, I can only provide generalities.

    FYI. Per your earlier comment, two 4" ducts provides less area than one 6" duct.
    Hope this helps. Let Us know what you do.

    Carl

  12. #27
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    Putnam ct
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    <p>
    Here is what I ended up building, the 6 inch main splits into 2 x 4 inch inlets (thanks Jim Becker), one on each side of the saw carrige. The curved back is UHDP. I tried neatforms scored 1/4 inch MDF but it did not want to bend into a small enuf radius. The plastic worked great. I assumed I would not be able to lean the saw over for compound cuts so I made the hood removeable; it will sit on the benchtop that supports the saw when I install it in a bench. As it turns out, I CAN tilt the saw over, oh well. The hose off the blade is the Rockler mini-dust rite, it will connect to a cheap shop vac or maybe I will tie it into the DC system. I am moving in a few months so I have not been able to try this out yet, hoping it will work OK. Not looking for no sawdust, just want to contain the small particles that migrate everywhere around the shop, hopefully there is enuf volume and velocity to suck that stuff down and out...we will see, I will report back.</p>
    Attached Images Attached Images
    Last edited by stan shields; 12-05-2017 at 12:52 PM.

  13. #28
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    Cool. Cant wait to hear how it works!
    If at first you don't succeed, redefine success!

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