A guide to dust extraction

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siggy_7

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I've attached a spreadsheet that performs the basic design calculations for sizing a blower. I'm not sure that I have recommended a particular motor power in this thread (correct me if I'm wrong). Generally though, you can see the flow rates required for different diameter ducting to keep dust in suspension with a flow velocity of 20m/s given in one of the posts above. Working with fairly standard 4" ducting for medium-sized machines that the hobbyist will typically use, you need a flow rate of at least 565m³/hr, which is right on the limit of a 1hp motor if you want to provide a half-decent 2-2.5kPa stall pressure (and especially if using an inertial separator, which if properly sized with have a pressure drop of around 1.5kPa before you account for flow losses elsewhere in the system).
 

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MilesH

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Starting to think about building my own extraction system.... Does anyone know if there are any significant differences between the design of fans for fume extraction and those for dust/shavings extraction. Secondhand centrifugal fume extraction fans often come up for sale.
 

Chippymint

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It's very pleasing to see a detailed article on this subject and well put together. I hope readers aspiring to achieve a satisfactory dust extraction system will take the time and trouble to read this as part of their on going learning into what is a reasonably complicated matter. Furthermore, getting this right for a workshop will hopefully prevent them from contracting respiratory diseases and/or irritants that could see them having to remove themselves from their beloved woodworking environment and worst still; their livelihood - believe me it's real as I have a few ex craftsmen Woodworkers friends who have severe respiratory health problems who admit they got their dust extraction environment wrong.

Too often this subject is underestimated and misunderstood which easy to see when reading articles in many woodworking forums. The root cause seems to be the lack of or poor research and then applying what has been learnt. How many buy or lend a book that deals effectively with dust extraction in a workshop environment or seek professional advice? Such books are relatively cheap probably £15/25, which is super value and it's there for reference and does help.

Siggy 7. Your article is very good. A few areas that is not covered and many do not refer to are: 1. At source dust capture 2. Secondary air filtration (the invisible killer).

1. It's very important to realise that one can have an effective dust extraction system in itself but it could be let down by the machine manufacturers dust ducting design - Mitre saws, Table saws to name a few are typical of how little thought a manufacture puts into making sure we are protected or not - which is seen when we use these machine. These alarmingly poor designs are due to not having an effective legal Regulation placing a specific high standard and duty of care on the manufacturer to protecting our health. It therefore goes without saying that part of any dust extraction design should include reveiwing what, if any, further modification needs to be done to improve getting the dust from the machine to the main duct? These take many forms. Some solutions are simple and others not but don't let it put you off having a go.

2. Secondary dust control is rarely mentioned in woodworking forums, yet this can be the invisible killer. Has anyone (after a busy day in the workshop, using a multitude of machines with effective extraction working and then cleaned up properly) gone into the workshop, the next day, and found surfaces speckled with fine dust? If you have you will probably need to install a secondary dust filter system and/or wear a mask more often than not. In honesty, a secondary air filtration system should be installed if you care about your health as you will be breathing in this invisible dust whilst working.

Yes, I think you can go on and on with protection but all we can do is minimise any impact on our health and if you are going to the trouble and expense to extract dust, by what ever means, then surely it should be done properly by having an end to end solution.
 

Peterm1000

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I have a HVLP dust extractor in a small shed attached to my garage. A 100mm pipe goes through the wall of the shed into the garage and I therefore extract the dust externally. The extractor has a cloth bag on it. Given that the dust is extracted outside (and I am OK with heat loss), is there anything to be gained by replacing the cloth bag with something less restrictive like a pillow case? Presumably, if I have no bag at all, then the small shed will just get filled with dust.
 

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