Manual of Purpose-Made Woodworking Joinery

Edge joints 47

about 75mm) a few times until a resistance to move-
ment is felt. At this stage, push slowly and stop when
the two mid- area marks are lined up. Whilst rubbing,
your fingertips should protrude, if possible, below the
thumb- held holding of the top board, to act as fences
guiding the two faces to a flush alignment.
After carefully wiping off the exuded glue with a
damp linen cloth, the jointed boards should be left for
about five minutes to achieve an initial set. Then they
should be released from the vice and very carefully laid
and cramped up in two, three or more sets of cramps,
according to the boards’ length. Prior to this, as men-
tioned above, the top, mid- area edges of the cramps
should be covered with masking tape or paper in the
area of the wet joint.
After being left overnight, or for at least 12 hours
to set (although bear in mind that the manufacturers
of PVA adhesives usually recommend 24 hours setting
to achieve full strength), the jointed boards should be
ready for minimal resurfacing prior to being gauged and
planed to width, then thicknessed to the finished size.

Gluelam joints

Figure 3.47: Gluelam (glued and laminated) con-
struction (also referred to nowadays as ‘engineered
wood’) uses any number of narrow strips of timber
(laminae) – of softwood or hardwood – with their
side edges glued and laminated together to build up
whatever width is required. Providing the appearance
of the multiple edge- joints is acceptable on a particu-
lar job, and the growth rings of each piece have been
placed to oppose each other, as illustrated below (to
combat unequal shrinkage and surface distortion), this
is an excellent way of building up and stabilizing wide
surfaces.

Figure 3.47 Gluelam board or ‘engineered wood’.

Origins of gluelam

This method of edge jointing developed in the con-
struction industry (predominantly in countries other
than the UK) about five decades ago and was used by
specialist manufacturers of gluelam beams and roof
trusses in the form of arched ribs. The laminated arch
shapes were formed in large jig arrangements, using

synthetic resin adhesives. By virtue of being bonded

together, the relatively thin laminae held their curved

shape after the adhesive had set.

This principle was also used by manufacturers for

producing bentwood components in furniture making.

For joiners and cabinetmakers interested in forming

bentwood (curved) shapes, the thickness of the

laminae is determined by dividing the radius by 150.

For example, a bentwood segment of 600mm radius =

600 ÷ 150 = 4mm thick laminae. When making the jig

or formers, it must be remembered that the radius for

the inner, (convex) former is different to the radius for

the outer, (concave) former. The difference equals the

overall laminated size of the component. This has to

be added to the inner radius – or subtracted from the

outer radius.

Finger- jointed/engineered wood

Nowadays, gluelam construction is used widely by

furniture makers and manufacturers of hardwood

kitchen- worktops, etc. In straight (uncurved) work,

the separate laminae are of relatively short lengths

which are either ‘finger jointed ’ or butt jointed on

their ends, before being butt jointed together on their

sides. For obvious structural reasons, the end- joints

are randomly staggered. The lamina are usually 18mm

to 25mm thick across the face of the built- up board,

but there are no hard and fast rules about this – except

to say that the board is less prone to distortion with

thinner laminae.

Gluelam work, whether for forming wide boards

or making shaped work, is easily achievable by the

individual craftsperson. The joints on the ends of the

end- jointed lamina – if required on lengthy work –

can be neat end- grain butt joints or neatly- cut 45°

splay joints.

Dowelled- edge joints

Figures 3.48(a)(b): The preparation of the boards’

edges for these joints follows the same initial pro-

cedure described above for butt joints. However,

although dowelled- edge joints were traditionally used

to reinforce the joined edges and create flushness

on the face side, they are – as mentioned above for

dowelled- frame joints – difficult to achieve by hand, but

relatively easy with the aid of an inexpensive dowelling

jig and/or with the availability of a pillar drill.

Before moving on to current methods of edge-

jointing, it must be mentioned that un- dowelled,

rubbed butt joints are still popular in small workshops,

but they are awkward to achieve and handle beyond

a certain length – of about a metre. This is where the

dowelled edge can help: on jointing longer boards.