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.
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.