This Whole Micron Thing

Dust collector manufacturers insist on describing their products’ performance in terms of microns. But how relevant is that from a health perspective? Actually, it’s a pretty good arbitrator…
A micron (um) is one millionth of a meter, which is just 1/25400th of an inch. Some manufacturers claim that the smallest sawdust particles are a whopping 30 microns in diameter, so a collector with a 30-micron bag is perfectly safe. But that doesn’t hold up in lab tests. For example, a paper that was published in 2000 by Elsevier Science Ltd on behalf of the British Occupational Hygiene Society reported that “approximately 30% of MDF dust collected was respirable (i.e. below 10 um)”. Not surprisingly, the study also found that dust from sanding was a lot smaller than dust from sawing, and finer grits produced finer residue. In addition, “MDF produced more dust in sanding than natural wood. Pine gave the least dust in both sanding scenarios and oak generated about 30% less dust than the MDFs.”
So, the material that you are working with matters, as does what you are doing. Surprisingly, none of the dust in the study was smaller than 1 um. But that’s not the danger zone. Dust below 10 um is very breathable, and this is what can cause cancers and lung disorders in humans. About 10% of the dust in the study was in this category. So, some of the dust from sanding MDF, hardwoods and softwoods can be dangerous.
Now, let’s look at filtration…
One of the more interesting aspects of dust size is that small particles (the bad ones) are more likely to go airborne. So, you’ll want to ‘scrub’ all of the air in the shop on a regular basis to remove these fine contaminants. The best way to discover whether your dust collector is actually doing a good job at this is to have the air tested. There are some very inexpensive tests available (from companies such as Greenhome). But perhaps a better option is to buy a basic tester from a company such as Dylos. If there are fines in the air, it’s probably time to talk to the pros because you might need to do some upgrades. When it comes to custom bags for dust collectors, talk to the designers at AFF. They can explain the whole micron thing, and why sometimes larger holes in the filter bag are actually better (because dust gathers on the inside if you go with a weave that is too small). That can mean that a 1 um filter isn’t always as effective as a 3 um one.
Several companies make ceiling-hung air scrubbing devices that are essentially just filters and a fan inside a box. There has been some debate about the effectiveness of these gizmos, but overall the expert opinions seem to say that they’re a good idea.

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Thoughts on Hand Tools

I’ve been working wood professionally for thirty-some years, and editing woodshop writers for almost as long. One common thread has been woven through the decades – the romantic nature of hand tools. Now, I say the following based on having taught sharpening and hand tool use for hundreds of hours (and even after popping in a picture of myself working several different planes, above)...
The romance is a load of old poppycock.
A block plane in the apron pocket is one thing: it’s a dab hand when faced with very minor tasks on a build, or even an install. But flattening boards or jointing edges by hand in the twenty-first century is verging on insanity. If you have that much time available, you need to spend some of it drumming up more business. I can see where a hobbyist might reap joy from creating the ultimate secondary bevel on a chisel, or salvaging a rusty old #5 that belonged to a long dead relative. Those are actions associated with tool collection and preservation. But once the plane is sharp and true, put it on a shelf and don’t let it waste any actual shop time.
When students used to ask me about the most important part of setting up shop, I always had the same answer: buy the most jointer you can afford. You can’t run a bowed edge against a table saw fence, but if the board is straight and flat, it will behave well on shapers, saws and router tables. I never once told anyone to buy a scrub plane. The woodworking profession is based on selling a service that customers are incapable of providing themselves. They have neither the tools nor the training. The service is usually measured in time – a shop charges so much an hour. If a jointer and thickness planer can render a board in less than a minute, why in the name of all that is holy would anyone spend a whole hour dressing and shaving with a nineteenth century remnant of pre-industrial apprenticeship?
For as long as I can remember, hand tool aficionados have been telling me that the finish looks different. And for years I bought into the myth that planes and scrapers cut across cells, while sanders merely abrade them and fill the voids with dust. Well, aside from the fact that wood cellular structure is pretty much beyond our range of vision, what professional doesn’t vacuum or blow the surface for dust before applying coatings? The depth of a finish, in my experience, comes not from mechanics but rather from the chosen coating. Oils that penetrate will usually deliver a richer result than plastics that merely lie on the surface. I’ve sanded and planed boards to see if people can spot the difference, and the results are inconclusive at best. Some species and cuts, such as the flaked ribbons in quartersawn white oak, seem to look exactly the same either way. A few richer species such as Claro may evince a very slight tonal difference, but certainly not enough to justify the enormous time commitment involved in, say, hand planing an entire dining table top.
The other argument put forward by hand tool fans (and many of my best friends are among them) is that the shop is quiet and peaceful without the intrusion of electric motors. My response is that a woodshop is no place for yoga, and if you need therapy that badly, you probably shouldn’t be around sharp objects.

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Art and Craft

Truly great masters have a mystical aesthetic that separates them from the herd. They produce work that simultaneously slakes our thirst for beauty and precision. But putting art aside, what defines superior craftsmanship? What is it about the great ones that sets them apart?
One common trait among the Maloofs and Krenovs seems to be an irreverence for the finite: like George Nakashima or even Charles Rennie Mackintosh, neither man was overly fond of tape measures. They followed the wood, using grain and color and whatever was available to sate their appetite for form. But others before them – the Sheratons and Hepplewhites – conversely rejoiced in the confines of fixed dimensions. They built to scale, to expectation.
Emerging from Victoria’s shadow, the likes of Mackintosh, Morris and Frank Lloyd Wright redefined restrictions. Their tall backs and floating horizontals pushed the edges of our expectations, simplifying form and even structure. Their joinery was more obvious, stronger, more enduring: meant to be used. Earlier builders had been contained by conformity – not just dimensions, but also decoration. The postures of elegance had required busy spaces, elaborate carvings, gilt, curves and complicated grace.
What is magical about most modern design is the ease with which it embraces comfort. Mackintosh and Lloyd Wright were the last of their kind to build uncomfortably. Function, for them, followed form. Today's best furniture artists are more concerned with utility: a chair must welcome its guests and encourage them to tarry.
Perhaps the essence of form meeting function, and art meeting craft, was the movement that borrowed the nomenclature. Arts & Crafts furniture evolved through the Gothic vision of Pugin, the socialism of Ruskin and the practicality of Stickley and Morris. In the end, it allowed the creative mantle to pass from architects to woodworkers. New ideas were born on workbenches rather than drafting tables, and with hand tools rather than machines. (Which is ironic: today, many of their designs have come full circle and are being built on CNC platforms.)
What set these craftsmen apart, and what later defined Maloof and Krenov, was an urge to impart not just things, but ideas. They were, at heart, teachers. Theirs was a democratic art-form, an everyman’s door where before there had only been windows. That open view attracted, and continues to attract, a wide swath of talent to the ranks of turners, carvers and builders. And the greatest of these are the ones who marry craft to art, who sense form rather than just measure it, and who follow the wood where it leads them.

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Table Saw Blade Height

Woodworkers have been using table saws for at least 240 years. The earliest patent seems to be Sam Miller’s application in 1777 that covered a saw that originated in Europe. About a century later the first commercial saws became available, including one from Illinois-based W.F. & John Barnes in its 1885 catalog. Power sources varied: early saws used leg muscles, and then water wheels before the advent of electricity. For as long as we’ve had circular saw blades, woodworkers have discussed the safest ways to use them. And how high to set the blade has always been on the top of the list. After almost four decades of running a saw professionally, my opinion is (and has been for a long, long, accident-free career) to set the height so that the bottom of the gullets (the scoops in the blade between the teeth) is ¼” above the top of the workpiece. This means that all of the blade’s geometry is engaged, with a minimum amount of the tips being exposed. (This is on a final cut: sometimes, an incremental cut or two are needed if the stock resists.) What new woodworkers MUST understand is that the greatest danger from a table saw is not touching the blade with a finger, although that happens all too frequently. Much more prevalent is kickback – when the blade catches in the work and throws it back at the operator. The most common reason for this is that the stock isn’t flat and straight. It must touch the fence and the tabletop all along its length. Both faces (the one lying on the table and the one running against the fence) MUST be jointed/planed before being sawn. A second reason is reaction wood, where the lumber was cut from a part of the log that was still under tension, and those stresses are released as the cut is opened. If you’re milling your own stock, those boards will come from large branches or a twisted or storm-damaged bole. If possible, use that wood to heat the shop… Anyone buying a table saw should take a very serious look at models that feature a riving knife. This beautifully simple device is a splitter that rises, falls and tilts with the blade, so one is not constantly installing and removing the factory splitter and pawl assembly – and leaving it off because it’s such a pain in the butt. A very economical way to add similar protection to a saw without a riving knife is to install the Micro-Jig Splitter. One last thought: if you’re pushing stock through a blade and it feels like work, you’re doing it wrong. The machine should be doing the work.

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