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The Woodwright's Guide: Working Wood with Wedge & Edge By Roy Underhill
Lapped Half-Blind Dovetail
These are the dovetails for drawers and casework, hidden on one side of the joint and exposed on the other. On the carcase of a desk, the top and bottom may be the same thickness as the sides, but their dovetails stop short, leaving unbroken the display of grain on the sides. Drawers also have an unbroken display on the front, but usually join pieces of unequal thickness — the sides and back being thinner than the front.
Drawers often have their bottoms set in grooves plowed into the front and sides. The bottom fits in this groove like a door panel, fastened only at the front and left free to expand to the back. The back of the drawer is cut short, thus allowing the bottom to move freely beneath it. At least that’s one way (some use little battens), but if you do plan to set your bottom in a groove, plow it into the sides and front before laying out the dovetails.
Only the front of a drawer has half-blind dovetails. The back connects with common dovetails, and since we just covered that, I’ll mention the back only as it arises in the sequence of drawer layout and work.
Lapped half-blind dovetails for drawers join the thinner sides to the thicker front. Because the sides are usually thinner, and because they take the tails, you can clamp several drawer sides together and saw them at the same time. That makes this tails-first dovetailing, as before, but with a different method of transferring the tails to the pins.
Set your marking gauge to the thickness of the drawer sides and back. With the fence of the gauge always riding on the end grain, run it around the ends of the drawer back, around the ends of the drawer sides that will join to the back, and then just on the interior side of the drawer front.
Reset the gauge for about four-fifths of the thickness of the front and, fencing from the interior face, mark it along the end grain of the drawer front. Finally, run this setting around the ends of the sides that will join to the front.
Old drawers may have just one or two big dovetails and two or three small pins. The regional variations are worth your study as well, so whenever you visit a fine home with locally made furnishings, always ask your hosts if you may examine their drawers. There is great individual variation within the larger historical trends.
Free from historical precedents, your own drawers may have any number of dovetails, and you lay them out in the same way as we did earlier. Include the groove within the body of the lower dovetail and it will not show in the finished drawer. Make the widest point of the pin sockets equal to half the thickness of the drawer front. A one-in-six angle is always appropriate.
Before you square the lines across the end grain, lay out the dovetails for the back of the drawer. Mark all the waste wood with Xs. Then, clamp the two drawer sides together and carry the lines square across both pieces. Drawer sides are rather thin, and if the other drawers are the same size, let them join the pack. You can gang saw dovetails — but not pins.
Make all the sloping saw cuts on the drawer sides with a fine saw, but don’t take out the waste wood just yet. You need the saw kerfs intact to transfer the dimensions to the drawer front.
Mount the drawer front upright in the vise with the groove away from you and superimpose the appropriate drawer side upon its end grain. Align the end of the drawer side with the line scribed along the end grain of the drawer front. Hold the side firmly in place as you place the saw back in each kerf in turn and draw it lightly back, leaving lines, transferring the dimensions to the end grain of the front.
Turn the drawer front around or lay it on the bench top and use a try square to drop perpendicular guidelines down from the edge. Mark the waste with Xs.
Place the drawer front in the vise with the inside toward you for sawing. You can’t saw the entire cheeks of the pins, but you can saw the diagonal. Your diagonal saw cuts may even extend into the visible parts of the interior of the drawer, but never through to the front.
As always, you want to saw just on the waste side of the lines, but here it’s perhaps a little harder. Drawing back the saw in the kerfs left accurate marks, but they are shallow grooves — very attractive to your saw. You must start and continue the saw on the waste side of these grooves, not in them.
The rest comes out with a chisel. Lay the drawer front flat on the bench and either pare back or chop out the waste with your chisel.
Drive in cross-grain cuts near the line and then split back to these cuts from the end grain and repeat until you reach the full depth. A skew chisel is handy to reach into the angle of the corners. For the final trimming, you may again find it more convenient to clamp the work upright in the vise and make bevel-up slicing cuts across the grain.
Finish off the drawer sides and back as we did earlier on the through dovetails. As your final cut before assembly, slightly bevel the inner corners of the tails to help them ease into their sockets.
Slip the bottom into place to hold the drawer square as the glue dries. You can glue the bottom into the groove in the drawer front, but never along the sides or back. Of course the long grain of the bottom board runs from side to side, directing any expansion from front to back.
"The Woodwright's Guide: Working Wood with Wedge & Edge" By Roy Underhill
© 2012 The University of North Carolina Press