In the previous article on this subject, I discussed the thorny issue of dust extraction, mentioning that this area is fraught with complexity, not least of which is that it’s the tiniest dust particles that do the damage and they are the ones that we should try and avoid ingesting into our tubes.
There are two methods to obtain good dust prevention. One solution is to work outside, where the atmosphere will rapidly degrade these particles and the other is to wear a close fitting respirator and blow the dust out of the workshop door at the end of the day with a large fan.
The vagaries of the British weather mean that both of these methods are probably not acceptable to most woodworkers, firstly because for much of the time during the cooler months it’s usually cold, wet and miserable. Secondly, it’s also not very neighbourly to blow a continual stream of dust and debris across the garden fence.
The question remains: how does the amateur or hobbyist go about constructing an acceptable system to capture (rather than prevent) dust inside the workshop, bearing mind that no system is ever perfect and it’s also in our interests as woodworkers to try and make our system as efficient as possible?
To begin with, I’ll describe my own dust extraction system which I assembled some years ago and thus far, it’s proved adequate but there is an improvement which I’m going to try and make shortly which will enable it to capture the finest dust.
My system based around a twin motor Camvac extractor fitted with 100mm diameter ports. It’s provided with a triple filtration system (two cloth and one brown paper filter) and the specifications say that it will remove dust down to a level of 0.5 microns. This figure doesn’t mean a great deal and should be viewed with extreme caution as the ‘capture rate’ isn’t mentioned and this can be can be quite tricky to understand.
In testing dust extractors to CE requirements, a known weight of dust (size 0.5 micron and larger) is passed through the machine and the residue in the air exiting the extractor is then weighed. The residue is calculated as a percentage of the original weight and it’s this figure that’s important; thus a machine such as the Numatic NVD 750 in a standard L class configuration will filter down to 0.5 microns, but also will capture 99.97% of the dust. When the same machine is fitted with an additional Hepa Module, its filtration level is equivalent to an M Class machine and will capture 0.5 microns at 99.997%!
The Camvac is situated roughly in the middle of the workshop but the collection bin isn’t really big enough, especially if there are a lot of chippings coming off the planer thicknesser. In order to increase the capacity, I use a 220 litre water butt fitted with a dustbin lid adaptor and I’ve glued in a pair of 90° elbows on the underside that face in alternate directions.
This arrangement will collect all the big chippings and larger waste, but the finer sanding dust from the Jet 16-32 drum sander and AT1628VS lathe pass through into the Camvac drum. As a result, the filters clog up very rapidly, which is slightly disconcerting as they need to be cleaned fairly frequently.
Branching out from either side of the central collection point is a pair 100mm clear pipes which on the left lead to the Jet 260 planer-thicknesser and lathe, whilst to the right stand a Jet disc sander, Jet 16-32 drum sander and a large Startrite bandsaw.
Each machine is connected independently to the Camvac via a series of blast gates and from time to time the slots jamb up with compacted sawdust, the result of which is that they don’t close properly which drastically reduces the overall suction. It’s occasionally worthwhile to take the system apart to clear out this dust either using a small Allen key or a piece of stiff wire (an old coat hanger is ideal). Where necessary, joints between pipework can be reinforced with duct tape and a few cable ties.
This has the effect of reducing the deafening racket from the brush motors, but if they’re also directed underneath the suspended floor of the ‘shop (or through a hole in the wall) a tiny quantity of the very finest dust can be expelled.
Next time, I’ll summarise the basic procedure and look at some Axminster products that could be used for a medium sized dust extraction system in the home workshop.