Dust collection is something that every small workshop struggles with. It is simply too important to ignore. Sawdust represents both a fire and an environmental health hazard and must be controlled. If you are at all like me, you hate dumping your shopvac, so the thing labours as it gets filled and clogged with all of the dirt which has been sucked up on previous days. Each day the vacuum moves less air, is less efficient and is closer to burning out from being over-burdened.
Dust Collection – Mission Impossible
Recognizing my laziness and the impossible task being asked of my lowly shop vac, I did some research. I came across a YouTube video from Ron Walters showing how to make a simple vortex or cyclonic collector. After a few hours and ironically huge amounts of sawdust from sanding all the beveled edges, I came up with this little creation. The wood is all scrap so my total investment was about $8.00 for the ABS vacuum extension wand from my local Home Depot. Ron had suggested using ABS pipe, but the extension wand is already the correct diameter to connect your existing vacuum hoses and is easily shaped to fit. The cyclone body was then attached to a wooden disk which snaps down snugly over a five gallon plastic pail and the entire assembly placed between my tools and the shop vac.
Immediately I began to wonder just how effective this simple device could possibly be as a first stage filter in front of my vacuum. I decided to begin an experiment. I carefully cleaned out my shop vac. I removed the filters and thoroughly washed out the canister. To get a really clear idea, I put the large cloth bag/filter through our washing machine. This did much to endear myself to my better half, but the bag did come out looking pristine and white. Now I’d be able to see exactly how much sawdust was getting trapped and by what part of the system.
Over the weeks to come I collected approximately four and half gallons of sawdust in my plastic pail(s). I can see through the plastic just enough to know when the pail is getting to be about half full. Simply swapping buckets minimizes the mess normally associated with cleaning out your shop vac. For demonstration purposes, I have combined the contents of the two pails in the image to the left.
The Surprise Inside
Of course the real test was to open the shop vac and see just how much dust had bypassed the vortex and made its way through to the main canister and filter. I have to say I was pleasantly surprised at the outcome of my experiment. The bag filter had only a few slightly discoloured patches where you could detect a very small amount of sawdust accumulation. Obviously this was catching some of the finest particulate matter before the air was exhausted through the fan. Prior to using the vortex, this filter would get caked with extremely fine wood particles. Looking down into the canister was the really big surprise. This photo is of the four ounce water glass into which I poured the entire contents of the canister.
Calculating the Efficiency of the Vortex
Using some very rough math and some very conservative estimates, I have approximately four and half gallons of sawdust in my vortex and less than an ounce in the canister. Let’s be very generous and say that the dust trapped in the cloth filter would fill up the glass enough to equal one ounce. These are Canadian imperial measurements so I have
4.5 gal x 160 = 720 oz in Vortex : 1 oz in canister
My results and calculations in this experiment would indicate the vortex is collecting 99.86% of the sawdust pulled off my tools and shop floor. This is approximately seven times less sawdust entering my shop vac than would be expected based on figures advertised by most commercial vortex vendors. From this I have to conclude that they are just being conservative and that my shop-made vortex is working at least as well as commercially made offerings.
I am about to upgrade my entire dust collection system to handle the increased workload in the Drakyn workshop. The first thing I will do is to build a larger cyclonic collector for the new four inch ducts. In addition to the obvious efficiencies in having a two stage dust collection system, the cyclone also adds one significant safety advantage. The use of a cyclone all but eliminates the chance of a bolt or other piece of metal from getting pulled into the metal impeller in your collector. A bolt sailing through your vacuum hoses could not only cause significant damage to your impeller, but could also spark and possibly drop an ember to smolder in the accumulated sawdust in your system.
I’d like close with a big thanks to Ron and would encourage you to check out his version of the cyclone separator.
Also see the updated article from 2014 on the current state of dust collection in the Drakyn shop.