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Accuracy Is Key

There are a lot of factors that go into making an accurate cut. Alignment of the miter table to the base, the fence to both base and table, and the blade to all of the above are just part of the picture. The manufacturing quality (including design, materials, and production tolerances) of the pivot assemblies and the motor are also important, and will affect how the saw will perform over time. Detents. The importance of miter and bevel detents depends on the type of work you do. If you need to create perfect geometric figures - custom octagonal wood window frames or trim, for example - you will want extremely accurate, rock-solid detents. For production work on paint-grade trim, however, that degree of accuracy is less important than having a detent that won't wobble even when you don't tighten the miter lock. And if you spend most of your time carefully finishing houses that aren't quite square, the ability to easily and accurately come a fraction of a degree out of a detent will be a deciding factor. A miter detent override (Figure 2) can be helpful for these close adjustments, but some saws are designed so well that this feature is not necessary.

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A miter detent override helps with adjustments close to the detent. When the override is disengaged the miter detents function; when engaged they do not.Blades and power. When a free-spinning blade is suddenly slowed down under load, the deceleration can create a slight instability, or "flutter," which may result in an unacceptable quality of cut (Figure 3). In the worst case, the blade will wander through the cut or create two distinct edges on the kerf, one where the blade entered and one where it slowed down under load. The severity of the problem varies depending on whether the motor is simply under-powered, or is underpowered but geared to spin the blade at a higher rpm than the motor can sustain. If both conditions are present, however, a clean cut will be a real trial. Inaccuracies can also be caused by operator error or a low-quality blade. Most instruction manuals recommend that you let the blade come to a full stop before raising the blade or removing the work piece. The blade deceleration at this point, especially with a brake, can once again cause instability in the blade and further detract from the quality of the cut. If you're just butchering dimensional lumber, none of these considerations matter much, but if you're making cabinet face frames, getting a clean cut is a big deal. In any case, nearly all of the saws reviewed here will benefit from the addition of a better quality blade, so don't forget to figure that into your purchase cost. Sufficient power is important for producing a good cut. Fortunately, we are seeing more power ratings in output watts, which is a more reliable indicator of power than an amperage rating. In general, horsepower ratings should be regarded with suspicion, since not everyone figures horsepower the same way. Also, on a sufficiently powerful motor, electronic speed control can contribute greatly to the performance of the tool and the quality of the cut.

Bigger vs. Better

The decision to go with a or saw again depends on personal preference and the type of work you do. All things being equal, a smaller blade may be more stable and consequently more accurate. Quality of design and manufacture can make a difference, however - a good 12-inch saw can be far more precise than a bad 10-inch saw. With compound miter saws, unlike their sliding brethren, there is a direct relationship between blade size and cutting capacity. But don't forget about the effect of an auxiliary fence. A piece of 3/4- or 7/8-inch stock against the fence can provide the extra vertical capacity you need. Likewise for horizontal capacity, if you add thickness to the bed. Bed, table, and fence design. Most of the saws reviewed here have some variation in production tolerances on the miter table to bed alignment, generally in the 0.012-inch to 0.017-inch range. This sort of misalignment can result in minor working inaccuracies that will be significant in some types of work but not in others. In the cases where a miter table and bed were perfectly aligned, I noted that in the comments. Bed design will affect portability, setup, and user comfort. When judging how easy it will be to carry a saw, consider not only weight and size, but also the shape of the saw and how many sharp edges you have to deal with. If you like to anchor the saw to a workbench, sawhorses, or a portable saw stand, make sure the manufacturer provides mounting holes that accept the type of fasteners you're likely to use. Finally, some saw tables are designed to match the height of a stack of standard dimensional lumber, making it easy to support a long work piece using materials already on site.