Finger-joints are used to join short pieces of wood together to form units of greater length. The joint is composed of several meshing wedges or “fingers” of wood in two adjacent pieces and is held together with glue. Finger-joined lumber is used for both structural and non-structural products. Structural uses include vertical studs in residential platform-frame construction (as a replacement for traditional dimension lumber) and the manufacture of glue-laminated timber. Non-structural uses include moulding and trim.
The wood pieces to be joined have the finger profiles machined, glue is applied and the joint is pushed together as the glue cures. This approach permits side grain to be glued together, which produces a much stronger bond than would simply gluing the end grain of two pieces together in a butt joint.
The fingers are cut to a greater depth in structural joints than in non-structural joints. The fingers may be cut parallel to either the wide or narrow face of the wood being joined. Appropriate glues are used for interior applications and for products that may experience exterior conditions.
Since the grain pattern along the length of a finger-joined stud is randomized by the inclusion of several shorter pieces of wood, the stud is less likely to warp than dimension lumber would. Finger-joined studs may therefore command a higher price than would single pieces of dimension lumber.
The stability of finger-joined lumber in changing external environments makes it desirable for uses in housing products that face both the interior and exterior of the house, such as windows and doors. With the use of finger-joined lumber in windows and doors having grown considerably in the past 20 years and an increasing number of firms producing it, finger-joined lumber has become more of a commodity product.
Non-structural uses of finger-joined lumber include moulding used in buildings, blanks for solid wood doors, picture frame material, and lumber for blockboard. Structural uses include stock for trusses, wall joists, blanks for glue-laminated beams, and flanges for wood I-beams.
Finger-joined lumber can be used in almost all the same markets and for all the same purposes as solid lumber. The joint can be designed to provide the appropriate strength characteristics for the end use. The market potential for finger-joined lumber is therefore very large.
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