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Cyclone build part 3 – the ‘Air Outlet’

The ‘air outlet’ takes the clean air out from the centre of the cyclone’s ‘upper body’. It is a fairly straightforward tube 75mm in diameter, 154mm long, and made by rolling up some 0.75mm thick polycarbonate.

The centre diameter of a roll of parcel tape just happens to be exactly 75mm , so here I use it to check my air outlet tube. Like the cone It is made from a length of 0.75mm polycarbonate sheet. Notice the edes are cut so they gradate and distribute the jointing forces, so that it makes a nice circle. We can also work out which way the air would want to be spinning and let the inner edge complement that.

Incidentally, with a fine toothed blade the bandsaw is doing a fantastic job with this stuff, some of which is slightly too thick to be cut with the magic tin-snips.

Here is the cutting diagram for the cyclones air outlet tube, click for a larger version.

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Responses to Cyclone build part 3 – the ‘Air Outlet’

  1. Bob Young

    A quick question – I appreciate what you have accomplished and published and was going to attempt a construct for my use. However, I find products here in US are in inch-foot dimension thickness and length/width and wonder if you think it would be a satisfactory separator built to the closest measurements derived from conversion to inch/foot metrics?

    Thanks for your time now and in creating web info.
    Bob Young

  2. Bongo

    Hi Bob, thanks for the comment.
    That should not be too much of a problem – as long as the measurement conversions are close…

  3. Colin Waters


    I am a member of a woodworking group in the UK – Southern Fellowship of Woodworkers (see and we recently had an evening where 3 members gave a talk to all the others attending on the subject of dust extraction. I gave a talk on my own workshop system where I use a simple Axminster dust extractor of about 2HP. But a friend has made a very simple separator which removes circa 90% of the dust on a system using the same extractor as mine. Therefore, I would like to build my own separator to your design but I need a 100mm diameter equivalent area inlet and a 150 mm outlet pipe.

    Could I scale up you design and still use polycarbonate sheet? I have read your comment on minimum radius possible with 0.75mm sheet but would a cone of larger scale have sufficient rigidity in 0.75mm sheet do you think.

    I think you have done a wonderful job on your website.



  4. Bongo

    Hi Colin,
    Sounds like you have a really good thing going on there with the SFW!

    Be aware that 90% material removal is not that good really (unless you are only sucking up very fine dust). For ‘general’ woodworking dust a simple drop box can achieve something like 90%, but it lets almost all the super small particles through (the ones that are most dangerous for you and clogging for your filter).

    You should have no problem scaling up the cyclone design. Use Bill’s spreadsheet to get the cyclone’s ultimate dimensions, then modify them so that you can make it from polycarbonate.

    I would suggest upping the thickness of the polycarbonate, as the radius of the cyclone will be larger – you could go 1mm maybe even 1.5mm. Then As long as you wrap the polycarbonate up in layers (one full overlap should do it), as I did, it should be fine.

    Let me know how it goes!

  5. Colin Waters

    Hi Bongo,

    Thanks for your comments. You are right that my friend’s separator is a simple drop box. So I thought that I would achieve much better results with a cyclone separator.

    I will try 1mm polycarbonate.



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