Creative Woodworks & crafts 2004-06, страница 20
continued from page 19 Jeweler's Blades You can cut metal with almost any blade, but the jeweler's blades are a better choice, and they really get small—just look at the 8/0 compared to the rest of them. 1 haven't found any blades smaller than that si/c. Choosing Blade Size Even with the great variety of blade types, one still must choose a blade size from each type. Determining the size to use for a given job is about as much of a decision as the type of blade. The smaller the blade size, the tighter the turn the blade will make. Tighter turns allow for more detail, so the amount of detail in a given project has a big impact on the blade size chosen for the job. 1 normally use the smallest blade possible for a job. Others teacli to use the largest blade that you can for a job. Either way of thinking can be right; it just depends on how you look at the results. Adjusting Tension The other thing we always question is how much tension is enough. Most of the manuals and books tell you to tension the blade and that is where they stop. How much tension to use is hard to describe and has to be experienced. 1 generally say that if the blade is wandering when you cut, increase the tension. If the blade is breaking within the first couple of minutes, the tension is probably too tight. 1 usually figure on a blade lasting 20 to 30 minutes, but I cut a lot in that time. Many say they can get about an hour of cutting from a blade. You will soon learn to tell when a blade is dull and needs to be changed. Naturally, used blades don't cut as well as they did when they were new. When a blade becomes worn to the extent that you begin having trouble following the line, throw the blade away and put a new one in the saw. Applying the proper tension is something you just need to get the feel for. When too little tension is applied to the blade, we can get what is normally referred to as a "barrel cut." The barrel cut shown in the cutaway pictured below was caused when the blade bowed from either too little tension or too much feed pressure (or both) when cutting. Barrel cuts are very aggravating. With a barrel cut. after you've cut your piece you can't slide it out the top or bottom of the scrap because it is locked into the wood. Your feed rate also has an impact on tension, depending on how aggressively you cut. The only way to learn it is to try different tensions—when the blade follows where you are guiding it and doesn't break right away, you have the tension right. Blade Clamps and Bent Blade Tips It has been found that blade clamps will sometimes bend the tips of the blades. Just use a pair of pliers on the blade's tip to straighten it out and thus extend the life of the blade. The little bend really becomes noticeable when doing fret holes. Once the bend becomes too great, the blade will'not feed tlirough the tiny holes. If your blades are doing this, you may need to look the clamps over for burrs and oil buildup. Periodically cleaning your blade clamps is a must. On the Delta Quick clamps I have learned that when you have the blade tip bending forward, the screw is bent in the clamp. Over-tightening the clamps will cause the screw to bend. So just replace the screw and you should not have the problem anymore. Other clamps may have burrs on the faces of the clamp that causc them to bend. A simple touching up of the clamp facc with some sandpaper may end your bending problems. Another cause can be the clamps that do not swivel. When you push your work into the blade too aggressively, the blades bend back and you will be constantly reaching for the pliers, and the problem gets progressively more aggravating as the blade gets dull. In Conclusion So if you are starting out, select a blade, set the tension, and work your way into the proper results: it's just a matter of feel and experience. ^ 20 • Creative Woodwork?; & Crafts June 2004 |
