|Forum topic by Don||posted 02-01-2007 06:54 AM||41525 views||18 times favorited||26 replies|
02-01-2007 06:54 AM
In one of my early blogs, I made reference to the dangers inherent in inhaling wood dust. Over the years, I’ve concluded that any small particulates that find their way into the lungs are a health hazard. We all know the risks to ones health from smoking, airbourne asbestos, coal dust, etc. And the claim is made by some that some species of wood are actually carcinogenic. Regardless of the scientific validity of these claims, any woodworker will attest to the fact that inhaled dust is not a good thing. Most of us will have experienced clogged nasal passages and even blood in our hankies when trying to clear the nostrils. This cannot be a good sign.
There are many steps a prudent woodworker will undertake to prevent dust inhalation. To name a few, there are various dust masks from the simple, inexpensive throw-away paper filters to the positive-pressure air respirators; there are central ceiling mounted air filters, and there are Dust Control Systems that can be simple or very complex. I have posted a link to Bill Pentz’ site where he discusses dust extraction systems with a particular emphasis on cyclone extractors. If you spend any regular amount of time in an enclosed workshop environment, it would pay you to spend some time reading the research Bill has done on the subject. He is the woodworker’s cyclone guru.
Regardless how good your dust extraction may be, there is still ambient dust that escapes these and settles on the various surfaces in the shop. (As an aside, I frequently don my air respirator and turn on my air filter and start blowing off all of the surfaces in my shop with compressed air. Some of it escapes outside my open door, and some gets cycled through the shop air filter where it is trapped. Unfortunately, some of it resettles back on on the same surfaces.)
This is where a good shop vac comes in. For clarity, I am referring to a portable vacuum cleaner that we use around the shop to pick up wood dust and wood chips; the stuff that gets away from the ducted central DC System. Unfortunately, most small shop vac’s suffer from dust clogging, and may eventually burn out. (Think of the dust bag as akin to you lungs.) A good mate of mine, Peter Jurrjens, who has a local reputation amongst woodworkers for being very innovative, borrowed the concept of the cyclone from central DC systems and adapted this to the shop vacuum. It’s known locally as the Jurrjens Mini-Cyclone.
In essence, he designed a pre-filter to remove the majority of dust and chips before they reached the dust filter bag of the shop vacuum. The benefits are many; a cleaner shop, less frequent bag changes due to the larger storage capacity of the cyclone, no loss of vacuum power due to clogging, and protection of vacuum motor preventing burn-out. This is a relatively easy modification that will take only a few hours to do, and cost probably less that $25.00.
The cyclone consists of a two-stage unit. The top stage is made up from plastic paint buckets and a large plastic funnel to form the cyclone section, the lower section is a metal paint bucket that serves as the waste/dust collector. A look at the schematic will help you visualize this. The hose fittings are common plastic plumbing fittings. Two hoses fit into the top lid. One runs to the shop vac, and the other is used to pick up the dust and waste around the shop. The action of the air circulating around the upper unit is caused by the funnel shape of the top section. When dust and chips are sucked up into the mini-cyclone, the heavier material falls immediately to the lower container. The cyclone action of the air-flow throws slightly lighter particles to the outside walls of the cyclone by centrifugal force. When this lighter material hits the walls, it spirals down the cyclone walls and through to the lower container. Only the very lightest of material finds it way up through the vacuum hose into the vacuum bag. In my experience, you can fill the larger cyclone container two or three times before needing to change the vacuum bag.
I am hoping that the schematic shown here is sufficient to inspire LumberJocks to make their own mini-vac systems. You will never regret taking the time to make this fantastic little shop aid. If you have specific questions regarding this, I will either answer them myself, or have the designer of the mini-vac answer them for you.
I am not bothering changing the metric measurements to Imperial. If you can’t relate to metric, then do your own conversion. [1” = 25.4mm]
-- CanuckDon "I just love small wooden boxes!" http://www.dpb-photos.com/