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  1. #16
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    Quote Originally Posted by elver View Post
    do you think of using large axial fans exhausting dust laden air? If there is room for large diameters are axial fans more efficient at moving air to evacuate dust, compared to our centrifugal systems used in dust blowers, or is the velocity too low to manage the speed at which the dust is exiting a 10000 RPM tool head?

    Seems like these large fans are used in spray booths. Per m3/hr they seem more energy efficient, if your not trying to achieve large pressures to push air through a filter.
    Correct - Axial fans are fine when there is no back pressure from restricted tools, cyclones or filters. When there is back pressure the axial fans fail badly whereas centrifugal blowers will at least keep moving some air. Just like manufacturers claimed DC flows, I would take all claimed axial fan flows with a few grains of salt.

    Even more efficient, compact, and quieter than axial are squirrel cage fans but they cost more. I have variable speed two squirrel cage fans in my shed for ventilation. One is up to 1600 cfm on my fume/welding bay/booth. The other is a 1200 CFM fan that vents at the top of the ceiling.

    Evap AC units make excellent ventilation fans

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  3. #17
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    May 2009
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    Quote Originally Posted by BobL View Post
    Correct - Axial fans are fine when there is no back pressure from restricted tools, cyclones or filters. When there is back pressure the axial fans fail badly whereas centrifugal blowers will at least keep moving some air. J
    Ok so maybe then an axial fan might cut it for a drawdown table or extractor hood- just fitted to pump all the fine dust laden air straight out of the shed into the paddock. Should I still be aiming for 1000CFM or more or do I need to chase a minimum velocity? (maybe adding a fudge factor of 0.7 for manufacturer lies)

  4. #18
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    Quote Originally Posted by elver View Post
    Ok so maybe then an axial fan might cut it for a drawdown table or extractor hood- just fitted to pump all the fine dust laden air straight out of the shed into the paddock. Should I still be aiming for 1000CFM or more or do I need to chase a minimum velocity? (maybe adding a fudge factor of 0.7 for manufacturer lies)
    More suited to a basic hood - less so for a draw down table - the holes will stymie the flow.

  5. #19
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    Got the mesh discs today from SandpaperMan.

    They look amazing! Almost see through.

    Might get a chance to trial later in the weekend.

  6. #20
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    Quote Originally Posted by elver View Post
    Got the mesh discs today from SandpaperMan.

    They look amazing! Almost see through.

    Might get a chance to trial later in the weekend.
    Sunday delivery.

  7. #21
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    Hmm - slack with my terminology: It was a Saturday delivery, but I got home Sunday to the package. However, a Saturday delivery in itself is a marvel too!

  8. #22
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    Quote Originally Posted by elver View Post
    Hmm - slack with my terminology: It was a Saturday delivery, but I got home Sunday to the package. However, a Saturday delivery in itself is a marvel too!
    You won't get any argument from me.

  9. #23
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    Updating my own thread:

    I got a bunch of mesh sanding dics. While excellent on flat materials, and they do let the machine suck up heap more dust, they don't work so well on long skinny things or profiles.
    It seems the loop side of the discs doesn't have enough stiffness to hang onto the sanding pad when I sand curved things. This means without warning the pads slip off and you tear into the wood with the hook side. Not great on soft timber when your up to 600 grit, at the end of a job..

    So I'm back to better dust extraction with a whopping great big sucking machine and a custom hood / box as well as using a connected at source vacuum.

    With respect to sucking fine dust - i did some experiments with straight through bag less blowers (*just shoot it out the shed into the paddock with a little flap of shade cloth to slow the exit velocity / reduce spread.) The results were pleasantly surprising - a 0.5hp machine doing this was waaaaay more effective at collecting visible dust when sanding on my lathe than my 2HP machine with clean pleated filter, so I think I will pursue this approach for my sanding box/hood. <Yes I know this is not a real test, and I just used a torch and low light to look at dust being sucked into the BMH, and it doesn't mean much> Hosing down the grass after each sanding session seems to bed the dust down into the soil, so not much dust lifts off on a the next windy day.

    Other than a dedicated sanding booth, I think this is the best I can do for now. The trade off is that this needs heaps of power. To run this I'll use:
    1500w on the 2HP dusty
    750w on the 0.5hp dusty
    2000w on the shop vac
    400w on the sander.

    Luckily I can run all this when the sun is shining and the solar on my shed pumping out power in excess of my export limits.

  10. #24
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    What about a delta sander? I have a Metabo DSE 300. I don't use it that much but when you need it, there is nothing else like it!

    You can hook up a vacuum with the included (well, mine was) dust collector port that replaces the stupid little dust filter cartridge that is utterly useless.

  11. #25
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    Im not sure a delta would assist much. I still need to remove a bunch of timber as dust, and my little makita 125mm ros with vacuum attachment seems to work pretty well.
    Maybe the delta miight not fling the dust out sideways so fast, but Im not sure. And I did just buy another years supply of discs for my 125mm sander. Like 5 mins ago!

    Once I did look at going festool, and was committed to a little small ROS, but then at the counter, I was about to pay for it and I got a price for the little custom clip on vac hose connector, and my $$ tolerance tipped over a little cliff. After mentally preparing for the cost of the sander, the extra was too much. I put it down on the counter and walked out a case of completed "purchase interuptus". I'm scared forever and never even looking sideways at the fancy grey and green stuff in the corner of the shop.

  12. #26
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    Quote Originally Posted by elver View Post
    Im not sure a delta would assist much. I still need to remove a bunch of timber as dust, and my little makita 125mm ros with vacuum attachment seems to work pretty well.
    Maybe the delta miight not fling the dust out sideways so fast, but Im not sure. And I did just buy another years supply of discs for my 125mm sander. Like 5 mins ago!
    You are right about the dust not being flung about with as much vigour. That, and the amount of suction with an attached vacuum, at the business end does not tend to leave a lot of dust. That number is not zero though.

    With the right grit abrasive, you can get quite aggressive. These are variable speed too.

    I bought mine many years ago to assist me with the restoring of windows in my house. The house had been left in bad repair and there was so much rot in the wooden windows I almost ended up making totally new ones in some cases. On others there were patches of dry rot that did not structurally impair the window and putting in a graving piece was just too difficult, so the use of polyester resin was appropriate. I used this in shaping hardened resin and graving pieces. 40 grit paper ripped through that stuff and the Merbau graving pieces I made.

    Quote Originally Posted by elver View Post
    Once I did look at going festool, and was committed to a little small ROS, but then at the counter, I was about to pay for it and I got a price for the little custom clip on vac hose connector, and my $$ tolerance tipped over a little cliff. After mentally preparing for the cost of the sander, the extra was too much. I put it down on the counter and walked out a case of completed "purchase interuptus". I'm scared forever and never even looking sideways at the fancy grey and green stuff in the corner of the shop.
    Understood! I don't think the 90mm ROS would be materially better than what you already have in terms of dust collection in this particular use-case. The Metabo is definitely not on that same shelf price wise!

  13. #27
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    Quote Originally Posted by elver View Post
    Other than a dedicated sanding booth, I think this is the best I can do for now. The trade off is that this needs heaps of power. To run this I'll use:
    1500w on the 2HP dusty
    750w on the 0.5hp dusty
    2000w on the shop vac
    400w on the sander.

    Luckily I can run all this when the sun is shining and the solar on my shed pumping out power in excess of my export limits.
    If it's just for sanding, I would replace the dusties with a couple of bathroom vans venting the shed. A lot less noise too.

  14. #28
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    For round things, perhaps try the Festool LS130 sander.

    Its linear and useful for doing stair rails and banisters. VERY useful! Back and forth, not ROS.

    Paddles are like these things.

    The pads can be exchanged for different shapes, or make your own custom shape (they sell blanks). I've also seen the pads for sale on AliExpress.


    I see them for sale all the time on Gumtree and Ebay, for they are rather specialised. They go quite cheaply.

    festool-ls130-eq-plus-duplex-linear-sander-240v6.jpg671af9f1-257e-11e5-80cf-005056b31774_800_533-700x700.jpg maxresdefault.jpg

  15. #29
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    Oooh that does look interesting. Second hand seems about $400 or so I think.

    I did make a downdraft box last night its got a hood at the back, partial sides and as small an area as possible. Connected to my 2HP chip collector with a hose that's too long and with unfinished (unrounded) holes in the table it was a good start. Its got lights in it to allow better illumination of defects and is quite nice.

    Certainly fugitive dust was much less than normal, but it was still underwhelming.

    When I round over the holes and pretty it up a bit I'll post some pics.

    Next steps:
    1. Round over the holes in the table and experiment with covering some up some holes to see if higher velocity airflow will help catch more dust.
    2. Shorten the connecting hose and pump the dusty hose straight out of the shed (after I move a bee hive from the flow path) bypassing chip collection completely
    3. Get a sander that doesn't spin at crazy speeds with a smaller / better directed fan, so that dust velocities are reduced. (Linear or delta perhaps - this is last on my list as I've just ordered a heap of new ROS discs..)

  16. #30
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    Default Plan B

    Another idea might be to use part of BobLs designs with a twist. His ideas are good.

    He suggested a belt sander, plus the BMH.

    I think his BMH's are the bees knees. I LOVE MINE! Its magic - not science


    I once saw a company in Sydney that made all sorts of mouldings. Rather than fart around with a hundred different profile sanding things, they used a machine that seemed to have brushes. One fed the object into it and it used a thousand fingers rotating to brush the thing silky smooth, regardless of shape.

    I've seen them once on thickness sanders for one pro model (name defies me now). It replaced the drum.....

    AANNYYWWAAYY..... the idea is you could hack together a box (to capture dust) and place one of these brushes onto an angle grinder, drill or other rotating-device-of-choice (such as... a motor!!) and make your own Low Cost Hack.

    Some cheapo thing like this off AliExpress (in a custom dust box) --> Emery Abrasive Brush Sanding Wheel used on Air Polisher


    Edit - This mob also sell add-ons for angle grinders (cowlings, handles and whatnot) as well as brushes of various size..... Hand held Linear Polisher Parts, Angle Grinder Adapter, Protective Cover, Bulgarian Extension Handle


    Edit 2 - Apparently these things are called LINEAR POLISHERS. These things are fantastic! Metal, timber, strip paint, fine sand, the works! All sorts of add-ons. Making up a dust box to capture the exhaust should be dead easy.
    5.jpg 1.jpg 3.jpg 2.jpg
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