A butt joint is a joinery technique in which two members are joined by simply
butting them together. The butt joint is the simplest joint to make since it
merely involves cutting the members to the appropriate length and butting them
together. It is also the weakest because unless some form of reinforcement is
used it relies upon glue alone to hold it together. Because the orientation of
the members usually present only end grain to long grain gluing surface, the
resulting joint is inherently weak. Methods
The butt joint is a very simple joint to construct. Members are simply docked at
the right angle and have a required length. One member will be shorter than
the finished size by the thickness of the adjacent member. For enclosed
constructions, such as four-sided frames or boxes, the thickness of the two
adjacent members must be taken into consideration. For example: when
constructing a four sided box made from 19mm thick material that is to be of
finished size 600mm x 600mm, two of the members will be docked at 600mm and two
will be docked at 600mm - 19mm - 19mm = 562mm.
Reinforced butt joints may require additional steps which are detailed
below. In solid timber, docking of members for
a butt joint is usually a crosscut, so a crosscut saw is best for this job. When
working with sheetgoods, there is no distinction between crosscut and rip
cut. The joint members can be docked by any
of the following methods: Carcase butt joints
Crosscut saw Circular saw and straightedge
Table saw Frame butt joints
Crosscut backsaw Miter saw
Table saw using a mitre gauge, crosscut sled, or sliding table attachment.
Reinforced butt joints To overcome their inherent weakness,
butt joints are usually reinforced by one of the following methods:
= Nailed butt joint= This is the most common form of the butt
joint in building construction. Members are brought together and a number of
nails are driven in to hold them in place. The technique of skew-nailing is
applied so that nails are not parallel to each other and so resist the pulling
apart of the joint. This form of butt joint is rarely used in furniture
making. Use for:
framing in building construction, such as platform framing
Basic or temporary boxframe making woodwork toys
= Dowel reinforced butt joint= The dowel reinforced butt joint or
simply dowel joint has been a very common method of reinforcing butt joints
in furniture for years. They are common in both frame and carcase construction.
Dowel joints are popular in chairs, cabinets, panels and tabletops. They are
also used to assist with alignment during glue up.
The technique consists of cutting the members to size and then drilling a
series of holes in the joint surface of each member. Holes are often drilled
with the assistance of a dowelling jig which aids in accurate hole placement —
accuracy is paramount in this technique to ensure members line up perfectly in
the completed joint. The holes are drilled such that there are
corresponding holes in each member into which short dowels are inserted with
some glue. The joint is brought together and clamped until the glue has dried.
This produces a joint which is much stronger than a butt joint without
reinforcement. The dowels offer some holding strength even after the glue has
deteriorated. Over time, dowels may shrink and become loose. They take on an
oval shape in section owing to the different rate at which wood moves with
different orientations of the grain. Loose dowels allow the joint to flex,
although it may not fall apart. This phenomenon is evident in creaking chairs
and wobbling book cases. For this reason, dowel joints are not preferred
for high-quality furniture. Use for: Frame joinery
Cabinet carcase construction Panel assembly
A variation of the dowel method for reinforcement is the use of a Miller
dowel in place of the usual straight cylindrical dowel. The Miller dowel is a
stepped dowel and is drilled with a special stepped drill bit. It is drilled
from the outside face of the frame piece to be joined and therefore generally
leaves an exposed dowel protruding after glue dries, and the excess dowell head
is thus usually flush cut. The advantages of the special dowel are
documented in various media promoting the method, but one advantage that
should not be overlooked is speed of assembly. The butt joint can often be
joined temporarily and sometimes more accurately with simply glue, allowing
faster set up than the usual tedious alignment procedures mentioned above.
After the glue dries one or more Miller dowels are then used to reinforce the
joint. Dowel trimming and sanding of the surface, followed by normal finishing
then proceed in the usual manner. The blind alignment problems of floating
dowels are virtually eliminated by the use of the Miller dowel. Not all
projects are appropriate for the stepped dowel method if an exposed dowel end is
not visually acceptable, however. = Biscuit reinforced butt joint=
The biscuit reinforced butt joint is a fairly recent innovation in butt joint
construction. It is used primarily in carcase and frame construction. The
biscuit is an oval shaped piece of specially dried and compressed wood,
usually beech, which is installed in matching mortises in both members of the
joint in a similar fashion to a loose or floating tenon. Biscuit joints are
common in both frame and carcase construction. They are particularly
convenient for panel glue ups as they facilitate alignment of panel members.
To create the mortise for the biscuit, a biscuit joiner is usually required.
There are other methods of cutting the slot, such as a slot cutter bit in a
router, but the biscuit joiner is the most common. Accuracy is not as
important in the creation of these mortises as the biscuit joint is
designed to allow a bit of flexibility during glue up. The mortise must be
located the correct distance from the face of the joint in both members but
the width of the mortise is not as critical.
When the mortises have been cut, the biscuit is inserted with some glue and
the joint is brought together, aligned and clamped. The biscuit absorbs some
moisture from the glue and swells up in the mortise, creating a tightly fitting
joint. Biscuits are available in a range of
sizes for different purposes. It is also common to use more than one biscuit side
by side in a joint when members are thick.
Use for: Frame joinery
Cabinet carcase construction Panel assembly
Attaching face frames to cabinets = Screwed butt joint=
The screwed butt joint uses one or more screws inserted after the joint has been
brought together. The screws are usually inserted into an edge on the long grain
side of one member and extend through the joint into the end grain of the
adjacent member. For this reason, long screws are required to ensure good
traction. These joints may also be glued although it is not necessary.
In solid timber work it is common to counterbore a hole in the frame or
carcase member to conceal the head of the screw. This also allows more of the
body of the screw to penetrate the adjacent member for greater traction.
After the screw has been driven into the joint, the counterbore can be filled
with an appropriately sized piece of dowel or a wooden plug cut from an
offcut of the same timber using a plug cutter.
There are also commercial systems available for screwed butt joints in
which a plastic cap is provided with the screw to be fixed to the head of the
screw after it has been driven home. Counterbores are not required for these
fasteners. This system is more common with manufactured board products.
The screwed butt joint is common in both frame and carcase joinery. Modular
kitchens make regular use of this fixing method.
Use for: Frame joinery
Cabinet carcase construction = Butt joint with pocket hole screws=
This is a variation of the screwed butt joint in which the screws are inserted
into pocket holes drilled in the rear face of one of the joint members. The
screws extend into cross grain in the adjacent member, so much shorter screws
can be used. This method is preferred when the edges of the frame will be
visible. The pocket holes require two drilling
operations to be completed. The first is to counterbore the pocket hole itself,
which houses the screw head within the member. This hole is stopped 1/4" or so
from the edge of the frame member. The second step is to drill a pilot hole
concentric with the pocket hole which extends through the edge of the member.
The pilot hole allows the screw to pass through the member and into the
adjoining member. This two stage drilling operation may be performed with
two different sized drill bits, however there are special stepped bits available
to perform the operation in a single pass. The drilling operation is often
facilitated by a pocket hole jig which allows the user to drill the pocket hole
at the correct angle and to the correct depth.
Use for: Frame joinery
Attaching face frames to cabinets = Knock-down fasteners=
Knock-down fasteners are a hardware device made for the purpose of
constructing butt joints that can be assembled and re-assembled repeatedly.
This type of fastener is very popular in flat-pack furniture, which is typified
by items such as book cases and wall units that come in a package of pre-cut
and pre-drilled components ready to assemble by a novice. They are also very
common in modern modular kitchens. Knock-down fasteners usually consist of
cam dowels locked by cam locks, also known as conformat fasteners, installed
in adjacent members. The members are brought together and the joint is
secured by turning the cam-lock. Specialist tools and jigs are often
required for the repeatable installation of knock-down fasteners, so they tend to
be limited to those who are making mass-produced items. However, there are
applications in which the hobbyist can benefit from the range of fasteners that
are available. They are easier and require less skill to install than some
of the other more traditional techniques.
Knock-down fasteners are typically used for carcase joinery; furniture designs
using them are usually of frameless construction.
Used for: Wide application in cabinet making
depending on type of fastener: particularly in carcase construction
External links Creating Butt Joints - DIY advice on
choosing and creating Butt Joints.