Woodworker's Journal 1982-6-5, страница 22




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Beginning Woodworker (cont'd)

that most parts that are tenoned on one end have a corresponding tenon on the opposite end and the distance between tenon shoulders is usually quite critical, so don't forget to take this into consideration when laying out the length of the tenons.

The usual procedure is to shoulder the tenon on all four sides, but this makes for a lot of extra work and more chance for error, so if possible, try to omit one pair of shoulders, preferably across the smallest dimensions of the workpiece.

A backsaw is used to cut two slots in the tenon as shown. These slots are located about 3/16 inch from the tenon ends and stopped about V* inch short of the shoulders. These dimensions are approximate depending on the type and flexibility of the wood and the size of the tenon. To forestall splitting it's helpful to drill a small hole at the bottom of each kerf as shown in Fig. 3.

The mortise needs to be tapered at the top and bottom to provide clearance for the wedged tenon. Fig. 3 shows how the mortise flares to the outside. The degree of taper really depends on the width of the mortised part but generally the mortise should be tapered to a slope of Vt to 6. In other words, for every inch of mortise depth it should slope 1/16 inch. A lot of woodworking books recommend a slope of 1 in 6 for wedges in general and this is fine for large removable wedges which we will discuss later, but most glued mortise and tenon joints in furniture look better with wedges that show as fairly thin stripes across the tenon.

Wedges are laid out and cut from scrap hardwood so that the grain runs lengthwise of the wedge (Fig. 4). The thickness of the stock from which the wedges are cut should equal the mortise width. Wedge length equals the

weeges -ace. cut voith ^kaim

f?onmimg lem^tmvoise.

after assembly. Note that the wedges are tapered along one side only; the opposite side is perpendicular to the ends. The degree of taper can be laid out by setting the thickness at the tip of the wedge to equal the width of the sawblade kerf. This is usually about 1/16 inch if a backsaw is used. The wedge taper is then made to a slope to conform with the mortise taper which, as previously mentioned, is 1/16 inch of slope for every inch of mortise depth.

When assembling the joint, glue is spread on all sides of the mortise and the joint is clamped up so that the tenon end is centered in the mortise and the wedge kerfs are accessible. At this point, from the outside, the tenon will seem far too small for the mortise. Glue is spread on both faces of the wedges and they are hammered in alternately, until you can feel and hear them seat solidly. Fig. 5 shows a cross-section of the assembled joint before the tenon and wedge stubs are trimmed flush and sanded.

Fig. v

TKiMMBT

Secne>MAL\/iew of assembled IWBLE wjed&ed m^rtise ftef^n

The blind or foxed wedge joint (Fig. 6) is a fine exercise in layout and cutting but in the "real world" of woodworking it is seldom used as it is difficult to taper the blind mortise just

FiCj-fc

depth of the tenon kerfs (including drilled holes), plus about Vi inch to al-

r__, •

_____i___n___l-

5ernismal View of bunp<?r f^xep

Cfc>ue>l_E WEDQEC MORTISE j TEM^in/

enough to allow the wedges to fully seat. If the mortise taper is too great

. !__' " Ml____• f____,1_____I______



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