Fence or Ambulance

I could have also titled this “Source or destination”

Would you prefer a fence at the top of the cliff, or an ambulance at the bottom?

Following on from the previous article, there is one thing that has been annoying me with heavy construction, specifically in occupied buildings. Unlike the precautions I take in my workspace (shed), there is so little (as in “none”) control of dust at the point of origin – the construction industry appears to rely on cleaning up afterwards rather than dust minimisation techniques.

While sanding down some of the walls in my home (part of the whole fix-up – I’m getting better at plastering), I’m using the Festool ETS 150/5, with a Cleantex CT36 and Oneida cyclone.  Just on startup, if you don’t wait for the vac to kick in, you can physically see the cloud of plaster trying to billow out, before being sucked straight back into the various ports on the ETS.  The rest of the job, there is no dust, nothing to clean up, even when sanding in the walk-in wardrobe – there was no dust on the clothes at all.  Let alone in my lungs.

Something like the industrial sized Microclene unit for a worksite

Microlene MC3000

or a small unit suitable for a workshop


This is one decent step towards capturing dust that is produced before it fills the room and settles on all the surfaces.

You can improve the collection further by adding a shield to the collector

mc1000-2or even place the unit right at the source of generation.

micro-3Whether that be an air filtration unit nearby, or on-tool dust collection, or a combination of both.

One way or the other, the results are always better when you actively mitigate dust production at the source, rather than cleaning up later.  What would you prefer – using and cleaning a filter, or using your lungs as that filter?

Wearing pleats in the workshop

As a general rule, wearing pleats in the workshop is not the best idea. Other than being just a little too frilly to be shed-like, you’d get a lot of really weird looks from visitors!


Of course, there is a place for pleats in the workshop, and that is in the cartridge of the dust extractor. So why would something frilly be a practical accessory in the workshop?

Many dust extractors use a cloth bag. Cloth bags are great. They are cheap, which is great. They are easy to clean, which is great. And they are great at spreading as much fine dust as you’d ever not want to see around the workshop. Sure, the large stuff gets captured, but that is stuff you can sweep up with a broom and shovel, so one way or the other it is easy to dispose of. The fine stuff will get you every time. In Australia, all wood dust is regarded as carcinogenic.

Many cheap dust extractors would have a cloth bag at the top and bottom. Awesome – two cloth bags to let the dust fly!

sealey-dust-extractor-2hp-240vIt is probably not fair to badmouth cloth bags too much – reasonable ones are running 5 micron, which isn’t much worse than what a pleated filter can achieve anyway.

So what is the advantage of a pleated filter?

A dust extractor pushes through a certain quantity of air. And what goes in, must come out. If you have a cloth bag, the air that leaks through the holes in the cloth to equal the amount of air that is sucked in the hose. As the holes clog, the total amount of air that will flow will decrease. So a filter that is easy to clean is an important consideration. Cloth bags can be banged out, blown out with compressed air, even washed in the washing machine. The limiting factor though, is the total surface area of the filter (the bag).

If you increase the surface area, the total amount of air that will need to pass through doesn’t change, so as the surface area is bigger, the holes can be smaller and still achieve the same through-put of air.

Where it comes to cleaning, pleated filters have a system where you wind or move a handle, that causes the internal baffles to be impacted, dislodging dust and allowing it to fall into the lower half (collection) for the extractor.

Pleated filters used to be only available on expensive dust extractors, but these days you can pick one up to retro-fit to your machine for under $180.

Considering a cloth bag replacement is around the $80 mark, this is a viable, and a superior option.

Even so, in saying that, any dust extractor that is allowing particles back into the workshop environment is not ideally placed. I get a bit of flack on here about my preference in not having the dust extractor in the main shed, but then I’m not breathing air that has been filtered to allow the lightest particles to remain. Once the dust-ladened air is removed, it doesn’t matter how fine the filter is.

However, when used in combination with a good air filter you can get the dust collection, and the air quality you are looking for, or at least closer to achieving the ideal.

So if you have a cloth-bagged dust collector, consider the pleat as a desirable fashion accessory, that is also a desirable feature improvement!

An eye on the dust

How’s your dust bag?

Mine? I know it is getting full. But there is full, and then there is full.  I’m sure I can fit the sawdust from just one more saw cut in there.  And again, and again.

I have the extractor in the attached shed: saves on noise, saves on the otherwise lost floor area, and any dust leaks (if any) don’t matter.  But it does mean out of sight, out of mind.

I finally got around to changing the collection bag.  What a mission! It was rather fuller than I thought, and it was cumbersome, heavy, and a right pain.  Yes, I know I should have changed it earlier.  Yes, I know I could have checked more often.  Coulda, shoulda, woulda.

A great pile

So.  I need to keep a closer eye on the dust collection.

One thing that’d help is to do a pre-separation.  By placing the pre-separation drum in the main shed, I can keep a better eye on it.  There isn’t the issue with dust escaping from the collector as this is not the end of the line, and the inside of the drum is maintained in a negative pressure.

Rerouting the corner

I had a bit of a win doing the rerouting necessary to fit this drum in.  Got rid of a MDF cabinet, fitted the drum in, and then while trying to think of what to do with the two sanders, I happened to notice the Walko sitting there which I had used at Ballarat and hadn’t gotten onto putting back into the other shed.  Perfect fit!  Sure, a bit cramped (where in my shed isn’t!), but a solution where I wasn’t sure if I’d find one.

Walko is in the house

Getting back to the dust collection, and added an extra feature: an electronic eye to keep a watch on the dust collection, and let me know when things get too full.  This one is pretty cool!  It is the Trupro Dust Sentry from Woodworking Warehouse.  It may seem like some others, but for one very unique, clever feature.  But more on that shortly.

The sensor

The sensor fits very easily – drill a hole.  There are nuts on the threaded sensor that fit either side of the mounting position, holding the sensor in place.  The sensor has a maximum range of 40cm, and that meant it found the other side of my drum.  However on the side there is a small pot, and that can be wound down giving a decreased range.

Mounting position

You could use that sensitivity range so the sensor pointed straight down to where the dust was gathering, building a pile towards the sensor, or you can side mount it (as I have here) so it ‘sees’ the pile when it reaches that height.  I may change this location when I change the lid, but this was a good trial point.  (Lid change discussion at end!)  When the lid is changed, I’m likely to mount the sensor looking down – means I won’t have to remove the sensor each time I wheel the bin out for emptying.

Sensor range

You can test the sensor by waving a hand in front of it.  When it ‘sees’ you, a light comes on at the back (and a signal is sent to the control box).

Control box

The control box has the circuitry inside, and plugs into the wall for power.  It has the audible alarm, and an adjustment dial – all to do with a very special feature of this specific dust sentry….but I’m still not quite ready to tell you what that is!


Mounting the control box is very easy – couple of screws in through the back into a beam.

Dust speed

Ok, ok, the special feature.  This dust sentry is unique (as far as I can tell), as it doesn’t get fooled when a large quantity of heavy dust flies past it.  This sensor can be tuned to ignore passing particles that otherwise give a false reading, and triggers only from the stationary dust – the true level of dust in the bin.  This sensitivity can be tuned to your particular requirement.


So here is the unit all set, ready to sense. Ready to keep an eye on the dust!

Lid change: well, once I got all this set up, it was all working well…..except the pile of dust in the bin didn’t seem to be increasing.  At all.

I did experience this when first playing with this lid a few years ago, and was mucking around with all sorts of combinations of plumbing fittings to create a swirling, pre separation thing.  Really can’t be bothered trying to fix a bad design this time, so am looking at replacing the lid with this one (also from Woodworking Warehouse).  Chalk and cheese on the design!

Jet 2 stage

Developing the Dust System

Another small development – from the overhead system from the bandsaw, it now leads across the shed to above the thicknesser and drum sander.  This drops down, picking up the outlets from these two machines before heading off to the dust extractor.

Picking up the dust generators

The diagonal clear pipe is from the overhead trunking. The drum sander feeds into the top of the Y section.  The trunking then leads to a second Y section which connects to the thicknesser.  Blast gates on each inlet obviously.

It has proved significantly harder to retrofit a new trunking system into an already occupied (crowded) shed.  It means the system is perhaps not as optimised as it could be.  Even though there seemed an excellent selection of parts in the trunking kit, more is needed.  Some longer runs use up joiners that would otherwise be needed for the components.  But I can’t knock having a system where everything actually joins together without duct tape fixes.

A roll of glossy, grey duct tape.

Rabbit Run Fixes

I still find the Rockler blast gate mounts superb, and provides a very secure system.

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