Tech Talk
What are the "Causes of Poor Tool Performance in woodworking tools"?
It is often said in the tooling business, that a half million dollar router is only as good as the last ten dollar sharpening on the bit it is driving. In essence this is true, but there is a lot more to tool maintenance than just keeping the edge keen. In any machining application a sharp cutting edge is critical, if any standard of quality and production level is going to be maintained. The edge has to be not only sharp, but it also has to be able to stay sharp as long as possible in the application for which it was intended. Therefore, the rest of the tool has to be able to support that cutting edge for its expected productivity. A tool's overall performance is judged by a combination of footage, speed and finish. That performance is based on not only how it was designed and built, but how all it's components are maintained.
Obviously, the first step in solving a problem with a poorly performing tool is recognition of the problem. If a tool (or blade) is not working properly, it is not always evident to the sharpener. It is not that uncommon to get a call from a customer saying "the blade only lasted 2 hours, so I sent it to you to sharpen, and now it's no better." The problem was that he didn't get any life the first time and assumed that either sharpening would solve the problem, or that whoever sharpened the blade would know that it hadn't been working up to par. Now, it has to come back a second time to find out what was really wrong. If you suspect something is not right, let your service company know. That way, if they are equipped and qualified, the blade will be pulled aside and checked to determine what the problem is - and there are several problems that don't relate to sharpness of the tooth that can cause poor cutting.Sometimes, however, poor tool performance is obvious and the sharpening service will pick up on it by merely looking at the tool. The following are some of the more obvious examples of "Red Flags" that should alert a sharpening service to a problem:* Severe burning (or bluing) on a saw blade body* Excessive pitch build up on one side of a blade only* Rotational scratching on the collar line of a saw blade* Lateral lines on the shank of a router* Saw blade gullet cracking * An excessive number of broken teeth* Uneven pitch build?up on the backs or gullets of the wings of a profiling, routing, jointing or planing tool * Excessive burning on one or more spots of a profiling tool* Heavily burnt pitch on a saw blade or cutter* Any obvious distortion of the body of the tool or bladeAll of these observations are indications that the tool is more than just dull. The problem could be caused by application, accident, or misuse, but what is clear is that just sharpening it won't improve the tool very much.Whether you have let the sharpening service know or they have caught the problem, the next step is for them to pull the tool aside and thoroughly examine it for such things as straightness, tension, clearance, symmetry, etc. Depending on the problem there are a number of things that can be checked and corrected (another article), but if the cause isn't evident to the sharpener, it should prompt a call from them to sort out, with you, what could be at the root. One of the things the end user has to be sure of is the quality of his sharpening service. Modern materials and equipment demand that cutting tools have to be sharp and accurate. By this we are talking about maintaining the integrity of the tool throughout it's life. In the case of a saw blade, it is absolutely critical that the profile of each tooth be sharpened equally and accurately to the original specifications. If not, it will result in an uneven load on the teeth, shortening blade life with very poor cutting. On routers and cutters the two most common problems we see are hook angles being changed through sharpening (this will cause the tool to cut at a different angle than it was intended), and uneven stock removal on each wing, sometimes resulting in 25% of the tool doing 80% of the work. Also, we often see a radius on the face of the wing, caused by poor grinding equipment or sharpening methods. All of these things will lead to bad cutting and more frequent sharpening and re- tipping.When a tool doesn't perform it is reasonable that your first thought is that it wasn't sharpened properly. But, if you are using a modern industrial sharpening service and these problems only occur intermittently, the odds are quite good that the cause doesn't relate to the sharpness of the tooth. It is more likely that the problem is associated to other components of the tool. Most qualified service companies should be able to sort out why it failed, and usually repair the tool.Correction: Quite a number of sharp eyes out there noticed the error I made in the last article (January) by referring to the "upward cutting of a Radial Arm Saw". Everyone knows (except apparently me) that radial arm saws cut with a downward action. What I meant to refer to was the upward cutting action of a sliding mitre saw. Although, I have been told, the practice in Europe is to use a radial arm saw opposite to the way we do - by pushing toward the fence, similar to the sliding mitre saw. Maybe someone could confirm or dispute that! by: Doug Reid, President, B.C. Saw
