CON2130 Supplemental Notes
CON2130 Supplemental Notes
CON2130 Supplemental Notes
MODULE NOTES
Furniture that is meant to be moved and cabinets that are fastened in place have
different types of construction. Furniture must be structurally strong on their own, while
cabinets are fastened to the structure where they are located to give them additional
strength.
Wood and composite materials available for use in the woodworking industry are
designated for specific purposes.
Solid stock hardwood products are pieces taken directly from a tree. Generally the
wood is cut and kiln dried, but not sized to width. The pieces are cut to maximize yield
from the tree. The material is rough cut to thickness. The thickness of this material is
based on the quarter system where one quarter is ¼”. Generally, the thinnest solid stock
is available in is 4/4. Common available thicknesses are 4/4, 6/4, 8/4, and 12/4.
Hardwood solid stock is used as edge band for cabinets, doors and drawer fronts, and
also for more expensive furniture. The more solid stock in the furniture, generally the
more expensive the furniture.
Most hardwood material is made in to random width boards. When solid stock is
ordered from the distributor, it is ordered by the board foot. A board foot is a volume
measure. One board foot is 144 cubic inches. To get one board foot, three
measurements are needed. For example, a board foot could be 12”X12”X1”. A board
foot could also be 12”X6”X2”. The boards can be in widths from 4” up to 24”. Boards
narrower than 4” are deemed an inferior product and sold for a cheaper price as narrow
stock.
Cedar is classified as softwood that is usually sold by the board foot. It is very soft but
resistant to rot, so it is used for outdoor furniture, decks and fences.
Plywood is available in various grades and for a wide range of uses. Sold by the sheet
(a common size is 4’X8’), the plywood is made of layers of wood held together by
adhesive. The layers are oriented 900 to each other, creating a very structurally strong
and stable product. The specific use of the plywood is mostly determined by what the
outer skin is made from.
Cabinet grade plywood will have one good face that will be seen, and one face that may
be another species of wood that will be hidden. By only having one high quality skin, the
cost of the plywood can be kept down, keeping the cost of the project down as well.
This is used for cabinets and lower priced furniture where the interior is not seen or
critical to aesthetics.
Furniture grade plywood is the most expensive of the plywood types as the two outer
skins are both made from a premium quality skin (also known as veneer). These sheets
are used in high end furniture and could have veneers such as walnut, maple, cherry,
and other hardwoods. Furniture such as cabinets to display items in a living room would
be constructed from this type of product.
Plywood can also have particle board or MDF cores, but they
are not as structurally as strong. These core types are much
cheaper. Inexpensive furniture and cabinets that are attached
to the building structure are often constructed using these
core types.
The sides of a cabinet can be attached to the bottom using various types of joinery. In
commercial construction, dowels are often used to attach the sides to the bottom. This
is accomplished accurately by using a line boring machine or a CNC Router. There are
several other fastening methods, such as confirmat screws and biscuits. A cabinet box
on its own does not have a great deal of torsional strength. That is achieved with nailers
when they are attached to the structure. The nailers are built into the box at the bottom
and top of the back of the box.
If the cabinet is to have a back, it can be hidden by locating the back in a dado groove
just in front of the nailers. A cabinet back can either sit in this groove in front of the
nailers or be rabetted in at the very back edge of the cabinet. In the case where it is
rabbeted in, the nailers will be visible and should be of a material to match the rest of
the cabinet case.
Generally, fixed shelves are either biscuitted or dowelled into place. Movable shelves
are held in place using shelf pins and sets of predrilled holes.
Additions to a Basic Cabinet Box:
A face frame is a type of edge finish where all of the exposed edges
of a cabinet are covered by a solid wood frame that is machined and
assembled as a separate element from the cabinet and then added
after the cabinet is assembled. This is considered a premium finish
as these are generally made from solid hardwood that is 19mm thick.
A reinforced butt joint is used to join these pieces. A butt joint is weak
structurally, so some type of strengthening technique must be used. A common practice
is to use dowels. To make a reinforced butt joint with dowels, all of the frame pieces are
machined to final size. Next, the dowel locations are marked and a dowel jig is used
with a drill to locate the dowels in exact location n. the frame is then dry fitted with
dowels and checked against the cabinet it is for. If no adjustment is needed, the frame
can be glued and clamped, scraped and sanded, before attaching to the cabinet box. A
common attachment technique is to use biscuits between the frame and the cabinet
box.
Plinth blocks can also be added to give a more traditional look to the
cabinet. Plinths are used primarily as a finish product at the top or bottom
corners of door frames to eliminate the need for mitre cuts. Even though
a plinth is a premium product, the use of them will speed the installation
process as all cuts will be straight and not mitred.
A cabinet case can also have doors and drawers added to it.
The addition of these is determined by the end use for the
cabinet. If you are building the cabinet for a client, they will get
the final say on which of these are to be installed as well as the style and the quality
they want these elements built to.
Mitre joints are used on cabinet doors and though they look
good, it is a very weak type of joint. Mitre joints can be
strengthened in a number of ways. The joint can be biscuitted,
it can be dowelled, and corrugated fasteners can be used as
well. A premium reinforcing technique that is used in high end
cabinet doors is to apply a spline to the mitre. The spline is
usually a contrasting material to the rest of the cabinet door
frame. These are visually highlighted while adding a great
deal of strength to the joint. Reinforcing a mitre joint has a
similar procedure to making a reinforced butt joint. The pieces
are machined to size, the reinforcing machining is completed, the pieces dry fit, glued
and clamped, then scraped and sanded.
Brad nails are a member of the nail family used primarily for finishing
purposes. Brads are generally 50mm or less in length and have small
heads so that they are easily hidden. The most common use for brad
nails are attaching backs on cabinets. For instances where pieces cannot be clamped,
such as attaching trim pieces on cabinet tops or face frames, brads can be used to
secure these pieces until the adhesive sets (glue dries).
Staples are used where a quick fastening technique is required. Staples can be applied
using pneumatic staplers. When a staple is used, it has very good holding strength.
Staples can only be used in areas where their presence will not affect the aesthetics of
the project. Staples can be used to attach cabinet backs, or for securing upholstery.
There are two main types of screws used in cabinet work. These are pan head and flat
socket screws.
A pan head screw is meant to be used where the head of the screw
sits on top of a surface and applies a squeeze pressure between two
pieces. With this type of screw, a clearance hole is drilled in the first
piece to be joined. The clearance hole is sized to allow the screw to
pass through without the screw threads grabbing. A pilot hole is drilled
in the second piece of wood. A pilot hole is sized so that the threads of
the screw will grab on to the wood. This pulls the pieces of wood together, acting like a
clamp.
Flat socket screws are used when the head of the screw must be flush
with or below the surface of the material. In situations where the screw
head is to be covered with a plug or button to hide it, these are generally
the screws used. The angle on the underside of the screw head allow it to sink in to the
wood. If the screw is to be sunk in to a hard wood, then a countersink must be used to
make a conical recess for the head of the screw to fi in to.
The clamping process serves three purposes when performing a glue-up. The clamp
pressure forces the glue into and around the wood pores, creating a lock after the glue
cures. The clamps also will press the joint closer together if the surfaces were not
perfectly machined. Third, the clamps immobilize the joint until the glue dries. Wood
glue reaches 50% of its bonding strength after 1 hour, but takes 24 hours to reach its full
bonding strength. If the glue-up is completed correctly, the glue joint will be stronger
than the wood around it.
Overlay doors are used extensively in cabinetry that is attached to the building
structure such as kitchen or bathroom
cabinets. An overlay door will either
completely cover the face of the
cabinet, or cover a portion of the face.
These doors most commonly are
attached to the cabinet with European
hinges. These hinges are hidden and
allow the doors to swing open, clearing
the frame as they open.