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manual abstract
On the other hand, if the bit is a large one, the cut is deep or the wood is hard to cut, the proper feed may be a very slow one. A cross-grain cut may require a slower pace than an identical with grain cut in the same workpiece. There is no fixed rule. You will learn by experience from practice and use. The best rate of feed is determined by listening to the sound of the router motor and by feeling the progress of each cut. Always test a cut on a scrap piece of the workpiece wood, beforehand. FORCE FEEDING Clean, smooth routing and edge shaping can be done only when the bit is revolvir_ at a relatively high speed and is taking very small bites to produce tiny, cleanly severed chips. If your router is forced to move forward too fast, the RPM of the bit becomes slower than normal in relation to its forward movement. As a result, the bit must take bigger bites as it revolves. "Bigger bites" mean bigger chips, and a rougher finish. Bigger chips also require more power, which could result in the router motor becoming overloaded. Under extreme force-feeding conditions the relative RPM of the bit can become so slow --and the bites it has to take so large --that chips will be partially knocked off (rather than fully cut off), with resulting splintering and gouging of the workpiece. See Figure 10. 10 TOO FAST TO0 SLOW Fig. 10 Your router is an extremely high-speed tool (25,000 RPM no-load speed), and will make clean, smooth cuts if allowed to run freely without the ovedoad of a forced (too fast) feed. Three things that cause "force feeding" are bit size, depth-of-cut, and workpiece characteristics. The larger the bit or the deeper the cut, the more slowly the router should be moved forward. If the wood is very hard, knotty, gummy or damp, the operation must be slowed still more. You can always detect "force feeding" by the sound of the motor. Its high-pitched whine will sound lower and stronger as it loses speed. Also, the strain of holding the tool will be noticeably increased. TOO SLOW FEEDING It is also possible to spoil a cut by moving the router forward too slowly. When it is advanced into the work too slowly, a revolving bit does not dig into new wood fast enough to take a bite; instead, it simply scrapes away sawdust-like particles. Scraping produces heat, which can glaze, burn, or mar the cut --in extreme cases, can even overheat the bit so as to destroy its hardness. In addition, it is more difficult to control a router when the bit is scraping instead of cutting. With practically no load on the motor the bit will be revolving at close to top RPM, and will have a much greater than normal tendency to bounce off the sides of the cut (especially if the wood has a pronounced grain with hard and soft areas). As a result, the cut produced may have rippled, instead of straight sides. See Figure 10. "Too-slow feeding" can also cause your router to take off in a wrong direction from the intended line of cut. Always grasp and hold your router firmly with both hands when routing. You can detect "too-slow feeding" by the runaway too-highly pitched sound of the motor; or by feeling the "wiggle" of the bit in the cut. DEPTH OF CUT As previously mentioned, the depth of cut is important because it affects the rate of feed which, in turn, affects the quality of a cut (and, also, the possibility of damage to your router motor and bit). A deep cut requires a slower feed than a shallow one, and a too deep cut will cause you to slow the feed so much that the bit is no longer cutting, it is scraping, instead. Making a deep cut is never advisable. The smaller bits --especially those only 1/16 inch in diameter -are easily broken off when subjected to too much side thrust. A large enough bit may not be broken off, but if the cut is too deep a rough cut will result --and it may be very difficult to guide and control the bit as desired, For these reasons, we recommend that you do not exceed 1/8 inch depth of cut in a single pass, regardless of the bit size or the softness or condition of the workpiece. See Figure 11. WIDTH OF CUT Fig. 11 11 To makedeepercutsit isthereforenecessaryto makeasmanysuccessivepassesasrequired, loweringthebit1/8inchforeachnewpass.Inorderto savetime,doallthecuttingnecessaryatonedepth setting,beforeloweringthebitforthenextpass.This willalsoassureauniformdepthwhenthefinalpassis completed.See Figure 12. 2ND. PASS 1ST. 2ND. PASS PASS Fig. 12 DIRECTION OF FEED AND THRUST The router motor an_ bit revolve in a clockwise direction. This gives the tool a slight tendency to twist (in your hands) in a counterclockwise direction, especially when the motor revs up (as at starting). Because of the extremely high speed of bit rotation during a "proper feeding" operation, there is very little kickback to contend with under normal conditions. However, should the bit strike a knot, hard grain, foreign object, etc. that would affect the normal progress of the cutting action, there will be a slight kickback --sufficient to spoi...