Tech Talk
Explain proper "Dust Collection"in woodworking?
Dust collection is one of the processes in machining wood that, once installed, is often taken for granted. The principle reason for dust collection is to maintain a clean environment, and keep the plant and equipment reasonably free of sawdust. But from the tooling side of this industry, we look at dust collection from a different perspective - namely the effect it has on tool performance.
Simply put, good dust collection systems make our tools look good. The faster the chip is sucked up the vent pipe, the longer the tool will last and the better the finish cut. Sometimes, when this is brought up in the field, we get the "what?planet?are?you? from?" look. But the fact is, the effect of a properly maintained system can be as much as a 50% increase in tool life. In routing applications, for example, every time the chip contacts the router bit - and on a two flute bit running at 18,000 rpm, it could be as often as 600 times a second - the wood acids, glues, and friction get to add a little wear to the cutting edge. Plus, the longer the chips are in the cut you increase the chance of pitch build?up on the back of the cutting edge. This reduces back clearance, causing increased friction heat, prematurely dulling your tool, and leaving an unsatisfactory cut.The problem is most apparent when routing through a board, because you are cutting in a 180° arc, producing more chips that have no place to go but up or behind the cut - which tends to plug up quickly if the suction isn't strong. This is a complete waste of a good tool. When you are sizing or shaping the outer edges, obviously you produce less waste because you may be cutting on as little as a 15° arc. Though the chip is more easily thrown out of the cut, you still want the sawdust removed as quickly as possible.The exact same results occur when sawing, particularly in enclosed or hooded environments. Pitch build?up on saw blades is one of the principal causes of friction that reduces blade life, and the rate of pitch build?up is directly related to the rate of chip removal. The changes in materials, machinery and procedures that have taken place in the woodworking industry in the last two decades have been enormous, as anyone reading this already knows. In many cases these changes have exceeded the upgrading of the dust removal systems. Feed rates are constantly being increased. For example, the feed rates achievable with spiral router bits (a subject we can deal with in a future article) produce much more waste, faster. However, more often than not the rate of dust collection is not considered when the rate of feed is increased. The most obvious example of changing materials is the increased use of particle board and MDF. Machining these materials produces much smaller, denser chips than the larger and lighter chips created by most solid wood cutting/shaping, requiring more CFM of air flow at the pick?up point. Adding to this is the fact that these chips are much more abrasive to your tools than solid wood chips, further reducing tool life.One of the biggest problems the dust collection people tell us they observe is that after the original system is installed, new machines are added and/or moved, and the "add?on" pipes are not installed properly or in the proper place in the system. This adversely affects the performance of the system, throughout the line. Another common oversight is the lack of, or improper use of, blast gates. Often there is as much clean air drawn through the system from non?operating machines with wide open or missing blast gates, as there is dust laden air. The result is a further reduction of pick?up where it is most needed. The cost of high quality tools, coupled with the cost of resharpening and the wasted downtime for tool changes, it only makes sense to adhere to manufacturers' recommendations regarding dust collection at every pick-up point. by: Doug Reid, President, B.C. Saw
