Saturday, November 24, 2012

V3.47 - Winter Time Static

You might have read this one before, but as we get into winter, static becomes and real issue so, here’s your (maybe twice yearly) reminder.

This week let’s talk about static electricity in your woodshop. I’m sure we’ve all experienced it when using our belt sanders, but it can show up on all rotating equipment and especially in your dust collector ducts.

Static electricity in a wood shop is mainly caused by two things. First is low humidity in the air. Static is especially troublesome in winter when the outside temperatures are low. A rule of thumb is the colder it is outside, the lower the humidity is inside a heated shop. As a result, static charge builds up easily and causes shocks when the electricity discharges through contact. The problem is even worse if a shop’s dust collection system exhausts its air outside the building. This builds an additional requirement for fresh air coming in and the fresh, cold air will have low humidity once it has been heated indoors.

The second thing that causes the static electricity problem is motion between two things. In the case of a belt sander, it is the motion between the belt, platen and pulleys that causes the build-up of electricity. In the case of the dust collector or Shop-Vac, it is the motion of the particles through the hose. There are two places where the charge can build up. One is in the machine the dust collector is attached to and the other is on the person who is operating it. Fortunately, grounding the frame of the machine will eliminate the buildup of the static charge. All fixed machinery, such as a table saw, jointer, planer etc., should have its frame grounded to a water pipe or at the very least, to the ground conductor or conduit sheath of the machine’s electrical wiring. Sometimes this is not possible, especially if the machine is electrically double insulated, as is the Shop-Vac.

Beyond grounding the machine, the best cure for static problems is to try to keep the humidity in the shop from getting too low. This can be done by using bag-type dust collectors that re-circulate the same air within the shop after the dust has been removed. These collectors will also reduce your heating bill. Other ways of adding moisture to the air, such as using humidifiers, are worth considering. Another thing you can do is wear shoes that bleed off the static charge rather than allowing it to build up.

Send your questions or comments to: and we’ll see what we can do to help you

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