Tech Talk
How can I Achieve "Good Clean Cuts on Melamine"?
One of the most common questions asked is how can we get a cleaner, chipfree cut in Melamine board on the table saw? The same question can be applied to any laminated or veneered board, but melamine is less forgiving and, therefore, the problem of chipping comes up more often.
A lot of chipping is actually caused by the surface fibres of the board. These fibres, unlike the core fibres, are supported only by the melamine surface, which is very thin and brittle. If the conditions of the cutting action are not right, when the saw tooth strikes these fibres it can easily push them through the melamine surface, rather than shearing them off, leaving a chipped edge. There are also situations where the tooth of the saw blade chips the material directly on contact. Whatever the cause, the chipping can usually be corrected by using good, well maintained equipment and a quality industrial saw blade.If you are not satisfied with the quality of your sawing, here are some of the things you should check.Any movement in the cutting action, such as a wobbling blade, will likely produce a rough surface, since each saw tooth is not hitting the board with a smooth, uniform and equal cutting action. Blade wobble can be caused by:* The spindle (shaft) is bent, or running on worn bearings.* Worn, bent, poorly made, or dirty saw collars. As little as 0.002" variance in the shaft or collar can cause as much as 0.04" run?out or wobble at the tip.* A bent, twisted, or out of tension saw blade.Next, you should check the fence. A good quality and true fence is critical if you want to achieve accurate, clean cuts. If it isn't straight or adjusted correctly then chipping will occur, and probably on both sides. There are many who believe that the fence should be parallel to the saw blade, and just as many who slightly offset the fence by about 0.004" at the back to eliminate any possibility of pinching the material. Whichever method you prefer, the fence must not cause the blade to "back cut" - where the teeth contact the material at the back of the blade as it comes up through the board. This action lifts the surface causing chipping on top. Make sure the blade is set so that the teeth clear the top of the material by approximately 3/4" to 1". You can fine tune this adjustment to your own preference but, at the very least, the bottom of the tooth gullet should be above the board by a small amount. This allows the saw teeth to cut at the angle they were designed to, shearing the fibres cleanly. It also helps to reduce heat and pitch build-up.A clean blade is an important factor in obtaining a clean cut. Pitch build up on the sides of the teeth reduces clearance, increases heat and adversely affects the quality of the cut by making the blade act as if it is dull.Feed the material at a rate that the horsepower of your machine can handle smoothly. Overfeeding bogs down the blade and reduces the rim speed, which not only adversely affects the quality of the cut, but also directly contributes to heat build?up which can cause blade wobble.Finally, check the blade. The integrity and accuracy of the tooth profile is critical, and the grinding has to be perfectly consistent. If it varies at all, the load on the teeth will not be consistent and chipping will result.Most table saws use a 10-inch or 12-inch blade and most experienced users will acknowledge that the following types are the ones commonly used.Triple Chip 72 or 80 Tooth. In combination with a scoring blade, this is by far the best method of cutting melamine. With scoring, your main blade will last much longer between sharpening and produce a consistently smooth cut. These blades can be used without the scoring attachment and should leave an excellent finish on the top; the finish on the bottom, however, will deteriorate too quickly.Hollow Ground (or Hollow Tooth). These blades produce an excellent cut top and bottom - probably the best or most forgiving, even when the machine condition is not as good as it should be. The downside is that they are more expensive to sharpen, blade life could be better, and they tend to perform poorly when the teeth are little more than half worn.Negative Hook 80 Tooth - Offered in triple chip or alternate top bevel. The alternate top bevel blades used for melamine have severe tooth angles which make the teeth very sharp, resulting in an excellent job of shearing the wood fibres at the surface. The only real problem with these blades is tooth breakage, because of the sharp angles ground into teeth. Any misuse of the blade can easily destroy it. Often the teeth break at the tip when someone uses it to cut a piece of wood with a small knot in it. The triple chip negative hook blades, however, are not so fragile. When the machine is in good condition and adjusted correctly, a negative hook triple chip blade will cut clean top and bottom. Problems with these blades seem to occur only when improperly maintained, or if the machine needs repair or adjustment.Some hints for quality cutting and good blade life.Use the blade diameter the machine was designed for. This is the only way to maintain the proper rim speed needed for clean cutting.Insist that your blade supplier sell you blades tipped with C4 micro grain carbide. For good blade life in cutting melamine coated boards, this type of carbide is essential. C4 is the hardest carbide grade and therefore the most brittle, making it unsuitable for cutting natural wood where knots and changes in density might impose intolerable shock loads that could break the tooth edge. This type of blade is available under several brand names.Consider using a blade stabilizer, which helps to support the plate portion of the saw and helps keep it straight. This becomes more important as the blade gets duller. The best quality ones are true and, as long as the shaft is true, the cut will be chip free. Stabilizers even help dissipate heat, which can cause blades to lose tension, bend and/or twist. by: Doug Reid, President, B.C. Saw
