# Measuring devices.

SQUARES

Used to check and mark right angles, squares are defined as steel or aluminum, try and combination. Combination squares will also measure 45-degree angles. If it has a degree scale, it can determine any angle.

* Framing squares, also known as carpenter's squares, are L-shaped and made from one piece of material (steel or aluminum), with the long end (body) usually 24" and the short end (tongue) 18". Similar squares are available in other sizes (8" x 12").

Squares may also have tables or scales, the most common being rafter and Essex tables. These provide information on how much lumber will be needed on a job, as well as information for roof framing.

* A try square or tri square is an L-shaped tool used as a guide for pencil markings of cuts and to check the edges and ends of boards to see if they are square. It is also used to determine whether a board is the same depth for its entire length. Try squares have broad 6" to 12" blades set at right angles, with wood, plastic or metal handles.

* A combination square combines the best features of the steel and try squares. It has a grooved blade and head that can be adjusted to many locations on the 12" blade to provide different measurements. The head usually contains one level vial and a scratch awl for marking. One edge of the handle has a 45[degrees] angle for use as a miter square.

Some combination square sets are available with an attached protractor that is movable throughout 180[degrees] for setting the blade at any angle within that range. Combination square heads (handles) are commonly plastic or metal.

* Miter squares measure 450[degrees] angles or bevels on one side of the square and 135[degrees] angles and bevels on the other side. Also available is a try/miter square, which features a 45[degrees] corner edge.

* Sliding bevel squares adjust to any angle and match angles being cut on the job site.

* Centering squares are used to determine the exact center of circles and other measuring angles.

* Pocket square is a small triangle with one thick, wide edge. It has different angle measurements marked on its surface and edges. It also works well at guiding power saws along wood.

Clarity and legibility of graduations is a key factor in choosing any type of square. Modern techniques enable manufacturers to etch graduations into the blade and create high-visibility markings that are durable as well.

* Rafter tables, which appear on steel squares, are used to figure lengths and cuts of rafters. The table consists of six lines of figures, with each line's use indicated on the left end of the square.

* The Essex Board Measure table, which also appears on steel squares, shows board measures of almost all sizes of boards and timbers. The table consists of six lines of figures, with each line's use indicated on the left end of the square.

TAPE RULES

For years tape rules have included two main types: tape reels and retractable steel tapes. In recent years, several types of electronic measuring devices have been introduced.

* Tape reels are typically 100' long and designed to measure long distances. They are contained in durable cases and rewound by a crank on the side of the case, with a small hook on the end for hooking onto objects to be measured.

* Retractable steel tapes or tape measures range in size from 6' to 35', with 12' and 25' the most common sizes. They vary in width from 1/4" to 1-1/4"--wider tapes are easier to use and extend over longer distances.

Because the tape rule is flexible, it provides an easy means for accurately measuring curved surfaces. The concave cross section allows it to be extended unsupported. Contained in the housing of most models are spring mechanisms that release or retract the tape.

Some tape rules include a spring clip for attachment to a belt and many have markings for laying out studs on 16" centers or other specialized markings.

Since blades receive hard wear, replacement blades or complete drop-in cartridge assemblies are offered to fit some tape rules.

For easier reading of complicated measurements, some tapes include fractional markings on the blades.

* Electronic feature tape measures and electronic tape measures are recent additions to this category. Electronic feature tapes are conventional tape measures with electronic features added. One such feature is digital readouts to make measurement readings more precise. Another electronic feature is a voice recorder to make it easier to keep track of multiple measurements. Electronic measuring devices have no blades but instead work on an ultrasonic or laser light principal.

* Ultrasonic measuring devices have a range of up to about 60'. The range on the laser tape is up to about 300'. The accuracy rating on the laser tape is to within 1/8". These electronic tapes often include built-in math functions, calculations and memory to store measurements. One of their advantages is the ability to easily measure linear dimensions to compute a room's square footage, which is helpful for estimating the right amount of wallpaper, paint or flooring needed.

* A chalk line reel is a coiled string of 50' or 100' contained in a metal (usually aluminum) or plastic box along with powdered chalk in various colors. It is used to mark long, straight lines on floors, ceilings and walls. Replacement chalk and string is available separately.

FOLDING RULES

Folding rules usually consist of 6" to 8" hardwood lengths connected by spring joints, but are available in steel and aluminum as well. Some have special plastic or epoxy coverings to protect the blade and printed numbers. Better models are painted with clear protective coatings over sharp multi-color printing and highlight commonly used markings for easy reading. Two basic rule styles are inside-read and two-way.

* Extension rules are used to measure closed-in areas such as doorways and window frames where a regular folding rule will not work. Extension rules feature a 6" sliding rule in the first section that can be pulled out to measure distances of less than 6" without moving and marking.

PRECISION MEASURING TOOLS

This group of tools contains such items as calipers, dividers, micrometers, thread pitch gauges and plumb lines. These items are used primarily by professionals, but are gaining popularity with hobbyists.

* Calipers and dividers are used for transferring measurements from a model to a part being produced. They can also be used to measure the inside or outside of holes or objects that cannot be reached easily with a graduated measuring device.

* Dial calipers and micrometers are used for close tolerance work using drill presses and lathes. These devices can make inside, outside and depth measurements to within .001".

* Thread pitch gauges are used to determine the exact thread pitch needed for replacing screws and nuts.

* An ultrasonic measuring tool is available that instantly measures room dimensions up to 50' away. It can calculate functions for compound measurements, area and volume.

* A plumb bob or plumb line is a small, tapered, pointed weight suspended from cord. It is used to measure true verticality or depth. Chalk line reels can also be used as plumb bobs, but are largely used to mark long lines on floors, wails and ceilings.

* Self-leveling laser plumb lines are available that project a vertical laser line onto any surface. The laser line is always visible because it is not covered up with a pencil mark and it is not affected by wind like a plumb bob.

* A carpenter's pencil is a wide, flat pencil that contains soft lead. It is used for marking measurements in construction projects. Its flat design keeps it from rolling around the job site. Also available now is a mechanical carpenter's pencil that eliminates the need for sharpening, as well as a marking tool that is water resistant, marks on most building materials and is erasable.

* A miter saw protractor makes it easy to do miter cuts. Set the saw to the angle that is read on the tool-the red scale and arrow show the angle for a miter joint while the black arrow and scale provide the angle to fill a single work piece to an angle.

STUD FINDER

Stud finders/stud sensors are of two basic types: magnetic and electronic. Stud finders are devices that help locate wall studs, enabling customers to hang pictures, mirrors and shelves securely. Magnetic stud finders do this by detecting the presence of nails or steel studs. Electronic stud finders do the same job, but they find the stud by measuring the density around the stud. Some advanced electronic stud finders will locate wood and metal studs, pipe, conduit, electrical wires and even reinforcing bar or rebar in concrete.
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