S E C T I O N T I T L E
Body
90° Squares:
Combination Square
The most common square, has a ruler with a groove running
down the center of one face. The combination head uses this groove
to lock onto the ruler at any point along its length. The combination
head features faces at 45° and 90° to the rule, a level vial, and
usually a scriber. The combo square is the most versatile, if not the
most accurate, of the squares. It can be used to mark, measure, and
set up ripping cuts, crosscuts, miters, dados, etc. Additional heads
available for combo squares include a protractor head for measuring any angle
or leveling any sloped surface, and a center finding head for finding the
center of squares, circles, or octagons. Prices for combination squares
range from less than $30 for a complete four piece set to over $80 for a
Starrett square with combo head only. Needless to say, you get what
you pay for, and only the more expensive squares will have accurate angles
and precisely etched rules. I have found many inexpensive squares out
of square by 1/16" over 10", and some even having only 15/16 in the
last inch on the rule. YIKES!
Carpenter's Square
The carpenter's square is simply an L-shaped piece of steel
with rulers marked along its inside and outside edges. Carpenter's
squares come in sizes from 9" to 24" along the longer edge. The scales
on carpenters' squares are often graduated in 8ths, 16ths, 32nds, 10ths,
and 12ths of an inch. Carpenters' squares are also useful for laying
out stair stringers and drawing arcs.
Try Square
Try squares are the traditional square of furniture and cabinet
makers. The typically have a steel or sometimes brass blade fitted
to a brass faced wooden stock. Most try squares have only the inner
face of the stock faced in brass, so this is the accurate angle. The
wooden back edge does not move evenly with changes in humidity due to the
rivets securing the blade, so the outside angle is not trustworthy. Some
modern try squares have wood covered brass bodies, so both angles are accurate,
and some squares are even adjustable in case they should be dropped. Try
squares come in blade lengths of 2" to 12".
Engineer's Square
This is essentially an all metal version of the try square,
and comes in similar sizes. As with try squares, the blade is ground
to ±.001" over its length.
Drafting Square
Not generally thought of as a shop tool, the draftsman's
square is still very useful in the shop. It costs little, but it is
still accurate within .01" over its length, and dropping it will not cause
it to go out of square. Available angles include 90°, 60°,
45°, and 30°.
Japanese Sashigane (Carpenter's Square)
This is very similar to the western carpenter's square.
Sashigane are designed for use with ink, so the edges are slightly
raised from the work surface so as not to smudge the ink. Also, the
rulers are marked in either the metric or sun (traditional japanese)
systems.
Miter Square
A specialty tool for accurately setting up and checking
miters when a combination square is not accurate enough, as when the width
of the miter exceeds a few inches. Looks like a bent T, with a wooden
stock like a try square for the vertical part.
Dovetail Square
A specialized square shaped like a T, with a thick body
for the vertical part. The blade is tapered on either side of the body,
usually with a 1:8 taper and a 1:6 taper for marking hardwoods and softwoods,
respectively. The square is set against the board with the blade flat
against its face. The taper sets the angle for the tails.
Bevel Gauge
Also called the adjustable bevel, has a movable blade that
can be set to any angle from the body, also useful for laying out dovetails
and setting up unusual miters.
Cutting Gauge
A cutting gauge is the tool of choice for marking lines parallel
to the edge of a board. It consists of a stock usually 4"-10" long
with a blade set in the end, and a body through which the stock passes, and
which sets the distance between the edge of the board and the marked line
by clamping itself to the stock. The blade of the cutting gauge is
beveled on one side only, with the bevel facing away from the body of the
tool. This causes the blade to pull the body against the edge of the
board as it is used. The blade usually has a double bevel on its one
side, making a sharp, V-shaped cutting point that will cut when the tool
is pushed or pulled. Some marking or cutting gauges use a sharp pin
rather than a knife, however, a pin does not cut cleanly across the grain,
and a knife also leaves a finer cutting line.
Mortise Gauge
The mortise gauge is essentially a double bladed version of
the cutting gauge designed for marking both sides of a mortise at the same
time. Mortise gauges typically use pins rather than blades, but since
they mark primarily along the grain, this is not a problem. The pins
are independently controlled, with the space between them variable from about
1/4" to a couple inches.
Marking Knife
The marking knife is the most accurate marking tool available
to woodworkers. It consists of a skewed blade beveled on one side only,
which allows the blade to mark exactly along a straightedge or try square
blade. Marking knives come in left and right handed versions, beveled
for use on the right or left side of the straightedge, and sometimes in
left/right versions, sharpened with a spear point, but still on one side
of the blade only.
Pencils
The two best choices of pencils for accurate marking are
carpenters' pencils and mechanical pencils. Carpenters' pencils have
a rectangular lead which is sharpened to a chisel point. This allows
the point to wear longer before it dulls, giving as fine a cutting line as
can be had with any pencil. Mechanical pencils are the next best thing,
offering ease of use and consistently fine lines.
Chalk / Lumber Crayon
These two are excellent for marking on rough lumber, or marking
rough cuts on dark woods where pencil lines don't show well.
Chalk Line
The chalk line is a simple way to mark a straight line
for rough cutting, even on the uneven surface of a log. Chalk lines
are mostly used where the surface marked will be removed or covered, as the
chalk is permanent on porous surfaces.
Japanese Marking Tools:
Sumitsubo (Ink Line)
This is the same idea as the chalk line, only more refined.
The line is actually silk thread, and leaves a fairly fine cutting
line without the hassle of holding onto a straightedge while marking the
line.
Sumisashi (Bamboo Pen)
The complement to the ink line, the bamboo pen is used
for layout with the sashigane (carpenter's square) and for lettering
pieces and joints for identification purposes.
Suji-keshiki (Marking Gauge)
Similar in design to the western cutting gauge, the main
difference is that this version uses a wedge to secure the stock, and it
is designed to be pulled along the board.
Copy Gauge
A copy gauge commonly uses steel pins held semi-rigidly in
a body to copy the profile of an object, a molding for example, so it can
be traced onto another object or pattern. It is used by first flattening
the pins against a flat surface, then pressing them into the profile to be
copied. The size of the pins determines the amount of detail that can
be copied by this method, and the length of the tool limits the length of
profile that can be captured.
Log Scriber
Very similar to a hermaphrodite caliper, the log scriber
has an "outside" caliper leg and a straight leg for scribing. Sometimes
the straight leg is replaced by a pencil, but the idea is the same: set the
legs apart as required by the shape being scribed, and hold the tool level
while following the contour with the "outside" caliper leg to scribe the
object to be fitted. Some log scribers come with level vials to assist
in holding the tool level, but with a little practice, good results can be
had without leveling aids.
Flexible Rule
This is basically a narrow lead bar with a plastic casing
around it, available from most drafting and art supply stores. The
rule can be bent to any curve not less than about 2" in diameter. Flexible
rules come with inch, metric, and no markings, and lengths range from 12"
to 24".
Inside Calipers
Used for measuring inside closed areas such as turned hollow
forms or drilled holes. Has two legs bent apart at the tips, and often
has a fine adjustment / locking nut to help it hold accurate
measurements.
Outside Calipers
Has two legs bent inwards, used mostly for measuring the
diameters of cylinders. Commonly has a fine adjustment / locking nut
to help it hold accurate measurements.
Hermaphrodite Calipers
A combination between dividers and outside calipers, used
for scribing and sometimes for marking parallel to an edge.
Inside/Outside Bowl Calipers
This is a double ended caliper, with an inside caliper
at one end, and an outside caliper at the other. It is designed such
that on end can be set on the work while the measurement is taken at the
other end. This makes it possible to measure the wall thickness in
turnings such as hollowforms, where removing the caliper would lose the
measurement.
Dial & Vernier Calipers
These are used for very fine measurements, when thousandths
of an inch count. Common uses include differentiating between fractional,
letter, number, and metric size drills; and setting up stack-type dado blades
on a tablesaw. Dial calipers are easier to read, featuring a large
dial which is read directly for the hundredths and thousandths. Vernier
calipers require some familiarity with reading a vernier scale, and a little
math to obtain the measurement. Both types of caliper can make inside,
outside, and depth measurements.
Straightedge
The straightedge is an often misunderstood tool, and its
name is frequently applied to the common ruler, which is rarely as accurate
for setup work. A true straightedge is a piece of finely ground and
tempered tool steel, straight and flat to ±0.001" over tis length, without
any graduations or index marks. It can be used for aligning tables
on jointers, tablesaws, planers, etc. and can be used when checking sharpening
stones and plane soles for flatness.
Hook Rule
Hook rules are handy for quickly measuring from an edge,
as they have a built-in hook that lines up the zero point on the ruler with
the edge of the material. The hook rule is a similar idea to the hook
on a tape measure, only much more accurate. On most hook rules, the
hook can be detached for use as a regular rule and for adjusting, if
necessary.
Center Finding Rule
The center finding rule features a scale starting at zero
in the center and counting upwards toward either end. The measurements
on either side are matched, and zero marks the center. Some center
finding rules feature a full size scale on one edge and a half size scale
on the other. The reading from the full size side is marked off the
half size side to mark the center of the board.
Zig-Zag or Folding Rule
Not popular, but still made and still handy, folding rules
can do a few tricks that combo squares and tape measures have yet to fully
match. Many folding rules have a thin, retractable metal strip
at one end for depth measurements in small holes or mortises. A folding
rule can be opened partway such that one or both ends stand perpendicular
to the work surface, allowing both hands to be used for setting up machinery,
and unlike the combo square, a folding rule fits in a pocket yet opens to
six feet in length. Folding rules come in wood and metal versions,
some with calipers at one end, and in lengths from two to six feet.
Tape Measure
The tape measure became popular in the fifties, and has
since become an indispensable tool for measuring anything over a few feet.
Tape lengths range from 3'to 30', and up to 100' in reel type measures.
The most popular sizes for shop use are 10' to 15', with a 1" wide
tape. The hook on the end of the tape slides by exactly its own thickness
enabling accurate inside and outside measuring. Magnetic "clips" are
available for convenient carrying on a belt without fumbling to reattach
the tape to the belt after use.
Compasses, Trammels, Dividers, Etc.
Compass
There are many varieties of compass, here I'll describe
the three most common types found in the shop. The first two are
transplanted drafting tools: the draftsman's compass and drop compass.
Both use a standard 2mm drafting lead, which is sharpened to a chisel
point. The drop compass is used for small circles under 1/2" in diameter,
and is less commonly found in the shop. The advantage to using these
compasses is the qualities that make them good for drafting also suit them
well to layout on projects: points designed not to mar the wood more than
necessary, fine adjustment for accuracy, and high quality, fine lines. The
other type of compass uses one sharp point and clips a wood pencil to the
other leg for marking. These are less expensive, but not quite as nice
as the beteer quality drafting tools.
Trammel Points / Beam Compass
Trammels are points or a point and a pencil holder that
clamp to a wooden beam for marking circles with radii exceeding 6". A
smaller trammel is typically called a beam compass, and comes as a complete
unit. Larger trammels come with the points only and the user supplies
the necessary length of beam. Higher quality trammels feature
interchangeable points and pencil holders, and a screw adjuster on one point
for fine adjustments.
Dividers
A pair of dividers is similar to a compass, but with two
sharp points for scribing arcs or stepping off equal measurements. A
loose leg divider is able to replace one leg with a pencil for added
versatility.
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