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  1. #31
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    Actually, Doug I am content for an either/or condition. However, if both conditions are met, so much the better.

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  3. #32
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    Quote Originally Posted by John Samuel View Post
    You are certainly on the ball, Bob.

    If I cut more slowly, the amount of material on the table reduces. If I cut very slowly, only the very dense (Vic Ash etc) or very resinous wood returns any material at all, but in much reduced quantity.

    Certainly, speed of descent of the saw is a significant factor.

    Another thing I noticed was the lack of a distribution of particles. Usually, we expect to see a distribution of particles from coarse to just barely visible, but that is not happening. The fine film of just visible dust I expected is missing. The particles all appear fairly coarse.
    The other aspect noted when cutting slowly is that the edges of the cut are smoother with less tear-out, as we might expect.

  4. #33
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    Quote Originally Posted by John Samuel View Post
    You are certainly on the ball, Bob.

    If I cut more slowly, the amount of material on the table reduces. If I cut very slowly, only the very dense (Vic Ash etc) or very resinous wood returns any material at all, but in much reduced quantity.

    Certainly, speed of descent of the saw is a significant factor.

    Another thing I noticed was the lack of a distribution of particles. Usually, we expect to see a distribution of particles from coarse to just barely visible, but that is not happening. The fine film of just visible dust I expected is missing. The particles all appear fairly coarse.
    Even when going slowly the saw will still be producing a range of particle sizes with more finer in relation to coarser particles. However, the overall rate of sawdust production (grams/sec) is reduced so the air stream is better able to pick up the dust and being more gas like, greater proportion of the fine stuff is cleared away leaving a few rouge coarse chips behind.

    When power tools (or wood) are pushed too quickly the saw dust particle size distribution changes considerably with a lot more tearing of fibres (ie bigger chips) as opposed to shearing or cutting. Blunt tools also change the particle size distribution - the most obvious place to see this is on lathes where chips can range from great long spaghetti fibres such to cornflour.

    Another way to test your system would be to change the TPI of your blade although smaller teeth will automatically force slower cutting.

    On Table saws there maybe a case for an air jet to be directed across the blade teeth inside the cabinet to blast away dust caught in the gullets and entrained in the moving blade airstream. This would reduce the number of chips sprayed outwards as the blade exits the cabinet and comes up out of the wood and the reason why blade guard collection is required. My air flow experiments around a TS guard show that the air flow is very much directed towards the operator which is why the chips come out in this direction. There are several reasons why I have not pursued the air stream idea. Air streams sprayed over moving blades can make a fair bit of noise and the larger sizes of the chips thrown forward and not a health issue.

  5. #34
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    That's my understanding too.

    I originally bought the saw to cut wall studs etc during a house renovation. It has an aggressive blade, which was fine when I had the zero tolerance fence on the saw. However, I could not get good dust collection with that fence, so the original went back on. A blade that is less aggressive and which creates less tear-out is on the shopping list. This should also help a little with dust collection.

    I considered getting a smaller Radial Arm Saw ... until I saw the price. Sharp intake of breath.

  6. #35
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    Default 4 inch lines don't suck (enough)

    The last machine that needs to have the ports upgraded to 150mm is the jointer/thicknesser. (In lower left corner of pic.)
    4 inch line to Thicknesser.jpg

    The black flexy from the thicknesser is 100mm. The red line is the path from the thicknesser to the cyclone.

    Usually, I crack blast gate 2 (to the drum sander) when using the thicknesser, to give better air flow. Yesterday I forgot to do this until several minutes of planing was done. When I remembered and cracked blast gate 2 a great slug of shavings shot into the cyclone.

    It is clear that the air flow is restricted by the 100mm line, and that when it hits the 150mm pipe it slows down enough so that material falls back along the line of the black arrow into the line to the drum sander. A thicknesser produces a bunch of shavings, and is probably the most likely of my machines to have this kind of problem. To test this, I closed blast gate 2 again for a couple of minutes of planing, and then opened it again. Another great slug of material shot into the cyclone.

    So, all the theory learned from the likes of Bill Pentz and BobL is demonstrated to be correct. Restricted air flow (from a smaller flexy or a poorly designed port etc) causes velocity to drop when the air hits an unrestricted 150mm line; this can cause material to fall out of suspension ... not the desired effect.

    I don't have an instrument to measure air flow, but I can measure amps. Here are this morning's readings (all at 60 Hz):
    1. Drill Press ... 7.2
    2. Table saw ... 7.1
    3. Vertical Sander ... 6.9
    4. Drop Saw ... 7.1
    5. Drum Sander ... 7.0
    6. Band Saw ... 6.9
    7. Thicknesser ... 4.1
    8. All blast gates closed ... 3.0


    Its pretty clear what that 4 inch flexy is doing to air flow.

  7. #36
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    Quote Originally Posted by John Samuel View Post
    It is clear that the air flow is restricted by the 100mm line, and that when it hits the 150mm pipe it slows down enough so that material falls back along the line of the black arrow into the line to the drum sander. A thicknesser produces a bunch of shavings, and is probably the most likely of my machines to have this kind of problem. To test this, I closed blast gate 2 again for a couple of minutes of planing, and then opened it again. Another great slug of material shot into the cyclone.
    This problem will remain whether you use 6 or even 8" ducting.
    Once dust is moving in a duct it is unlikely to move backwards in the manner you suggest but it can move sideways (see below). The one time it can move backwards is when the air flow stalls and then the dust remaining in the short length of duct between the main line and the junction between the sander and thicknesser can slide into the ducting to the sander.

    What is more likely to be happening when run the thicknesser and close the sander blast gate is the length of pipe between the sander and ducting between main line and thicknesser will experience a venturi effect and a partial vacuum. As the sawdust generated by the thicknesser goes past the junction to the sander some sawdust will be drawn by the vacuum into that section of duct. The same will happen the other way around but as the dust from the sander is fine it is less likely to completely clog the duct to the thicknesser. If you ran the thicknesser for long enough the duct to the sander could become so clogged that opening the sander blast gate might not clear it - it then becomes an disassembly job ie PITA.
    You do have a simple solution though and that is to partially crack the sander blast gate while using the thicknesser.

    Where possible blast gates near the machine should be avoided and placed as close as possible to the main line so as short as possible low vac volumes are generated in the branch ducting.
    Here is how I would have done it.
    To simplify matters I would probably have connected both machines using large flexy curves as the numbers of 90º bends needed using straight duct would probably probably add about the same resistance.

    Making 150mm DC ports for workshop machines-4-inch-line-thicknesser2-jpg

    If anyone about to set up their ducting would like me to check their system before they start cutting ducting feel free to post a plan or send me a PM.
    Cheers
    Bob
    Attached Images Attached Images

  8. #37
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    Thanks Bob,

    I actually thought about your suggestion during the design of the system. However, Bill Pentz's site recommended that at least a 4 ft length of uninterrupted pipe exist in front of the cyclone, to reduce turbulence of the air as it enters the cyclone, which is why the layout is the way it is. Perhaps I inadvertently chose the greater of two evils.

    Now I am up for a re-think. In any event, I need to re-think the positioning of blast gates. Being a firm believer in the old American axiom, "In God we trust, all others must bring data", I ran a trial by turning a sizeable lump of cedar into dust on the drum sander. Sure enough, a small quantity of dust accumulated just below the point where the sander and thicknesser ducts join. It was not a lot, but it was present, and I need to deal with the issue.

    Thanks again.

  9. #38
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    Quote Originally Posted by John Samuel View Post
    Thanks Bob,

    I actually thought about your suggestion during the design of the system. However, Bill Pentz's site recommended that at least a 4 ft length of uninterrupted pipe exist in front of the cyclone, to reduce turbulence of the air as it enters the cyclone, which is why the layout is the way it is. Perhaps I inadvertently chose the greater of two evils.
    Yes I would agree with BP on this one.

    Now I am up for a re-think. In any event, I need to re-think the positioning of blast gates. Being a firm believer in the old American axiom, "In God we trust, all others must bring data", I ran a trial by turning a sizeable lump of cedar into dust on the drum sander. Sure enough, a small quantity of dust accumulated just below the point where the sander and thicknesser ducts join. It was not a lot, but it was present, and I need to deal with the issue.

    Thanks again.
    No worries.

  10. #39
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    Default Spindle moulder

    The spindle moulder is now converted to 150 mm ports. (See pics.) Quite happy with the results. A little dust falls inside the cabinet, but it is only a tiny amount compared with that which disappears to the cyclone. Occasionally, a couple of chips bounce onto the table, but this is negligible.

    The gaps around the pipe seen in the second shot are deliberate. They allow a little more air to flow into the pipe.

    Any bright ideas on how this setup can be improved gratefully received.

    IMAG0102.jpgIMAG0103.jpg

    I use this setup to raise panels and to rout edges of cabinet tops etc. I need another setup to handle free-hand work like shaping cabriole legs etc, and have a design for this. Will post once done.

  11. #40
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    Quote Originally Posted by John Samuel View Post
    The spindle moulder is now converted to 150 mm ports. (See pics.) Quite happy with the results. A little dust falls inside the cabinet, but it is only a tiny amount compared with that which disappears to the cyclone. Occasionally, a couple of chips bounce onto the table, but this is negligible.
    I would not worry about big chips.

    The gaps around the pipe seen in the second shot are deliberate. They allow a little more air to flow into the pipe.
    These types of machines are PITA to deal with, so from the pics you have posted it looks like you have done a good job. About the only suggestion I would make is the same as I make to folk who uses sanders and routers and that is to (eventually) think about adding a extractor hood above the unit itself to catch any fine dust that billows away from these setups. This is difficult to do without visually blocking the cutting area.

  12. #41
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    Actually, the idea of an overhead hood is incorporated into the next port for free hand work. the plan is to extend to hood over the entire cutter and to fix a piece of clear PVC at about a 45 degree angle, so the line of sight is at right angles to the clear PVC.

    This means all the air being drawn in would be from the sides of the cutter, as the hood would extend over the cutter.

    More to follow when I get a prototype made up, but I am hopeful.

    Also thinking about a detachable clear PVC hood for the existing port. Needs to be detachable so bigger pieces can be passed along the fence, but for smaller pieces, it just might provide a barrier to prevent fines from rising ... they would be trapped in the airflow (I hope, the prototype will reveal more).

  13. #42
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    Quote Originally Posted by John Samuel View Post
    Actually, the idea of an overhead hood is incorporated into the next port for free hand work. the plan is to extend to hood over the entire cutter and to fix a piece of clear PVC at about a 45 degree angle, so the line of sight is at right angles to the clear PVC.

    This means all the air being drawn in would be from the sides of the cutter, as the hood would extend over the cutter. . . . .

  14. #43
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    Default Spindle moulder

    Made a new shroud for the spindle moulder today. It is for freehand work.

    The first pic is an overhead shot. I thermo-moulded some clear PVC to the shape of the pipe. The clamps holding the ply base will be replaced by 1/2 inch bolts.
    IMAG0127.jpg
    The second pic is a side view. I have a habit of over-engineering these things, and am pleased with the simplicity of this shroud.
    IMAG0128.jpg

    The third pic, from the front, shows the thermo-moulded base of the pipe to flatten it as well as how the ply base has been sanded into a ramp to reduce turbulence.

    IMAG0129.jpg
    It works like a bought one. Cut a 12 mm by 18 mm rebate in a piece of scrap and it left nothing at all on the table, as seen in the third pic.

  15. #44
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    Default Table saw

    Finally got an overhead blade guard/dust collector rigged up for my table saw.

    The first shot is an overview from the front. The entire assembly is supported on the fence rails, so the machine is still mobile and easy to move.
    IMAG0144.jpg

    The second shot is a closer view of the guard and the supporting arm. .
    IMAG0145.jpg

    The third shot shows the guard swung back out of the road. This takes seconds.
    IMAG0142.jpg

    It also takes seconds to remove the guard from the supporting arm, as seen in the next pic.
    IMAG0148.jpg

    Finally, the important shot ... showing my counterweight ... a coffee can full of water.
    IMAG0146.jpg

    A few finishing touches to come, but it is working now ... just like a bought one.

  16. #45
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    Great job John. Been wondering myself how to tackle overhead TS dust, you've given me some ideas. I'll be honest and say it looks a little unwieldy but would do the job well.
    Annular Grooved Nails....Ribbed for the Woods Pleasure?

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