A common requirement in woodworking is to join two pieces of wood together at right angles as shown on the right.
A common requirement.
The traditional way of doing this is with mortice and tenon joints (right). The mortice and tenon is one of the strongest woodworking joints. It is often called the ‘king of joints’. The strength is the result of the high degree of mechanical interlock and the large face-to-face gluing area. I would use no other joint for chairs and stools.Over the years, a number of alternatives to the mortice and tenon joint have been introduced. The motivation has always been to reduce the time to make the joint and to lower the skill level required. For many applications, these alternatives are more than adequate. Despite claims to the contrary, however, they do not match the strength and longevity of the traditional mortice and tenon joint.
The traditional solution.
If you don’t have a biscuit cutter, then a dowel joint is probably the alternative you would use. When strength is not an issue, I will take out my biscuit cutter. The face frame for the vanity unit (right) was made with biscuit joints. The frame in turn was biscuited to the carcass.
A biscuited face frame.
A few years ago, I was introduced to pocket-hole joinery by Trevor Williams of Woodfinish Management. Joinery does not get much simpler than this: drill it, clamp it and drive it. A few simple adjustments (based on wood thickness and screw length) and the pocket holes can be drilled in quick succession. The special self-tapping screws eliminate the need to drill pilot holes in the mating piece.
A pocket-hole jig.
The assembly stage is shown to the right. Here, the corner joint of a frame is being screwed up. The two pieces are aligned and held in position with a quick-acting toggle clamp and the two self-tapping screws are driven home.
Here, I am assembling an octagonal mirror frame. For a small frame like this, one screw per joint is sufficient. On a wider frame I would use two screws per joint. On a very wide frame I might use three screws per joint, but prefer a screw each side of a glued biscuit. The self-tapping screws act as internal clamps and I can move onto the next joint without having to wait for the glue to dry.
This will be an octagonal mirror frame.
Here is a reminder board for the kitchen (I must get around to making a larger one for my workshop). As can be seen, this board is made with pocket-hole joinery. It does not need the strength of mortice and tenon joints. The wider bottom rail has two screws per joint; the narrower upper rail has one per joint.
There is no such thing as a free lunch. The pocket holes are UGLY! Well, they are potentially ugly if they aren’t hidden. In the case of the octagonal mirror frame and the reminder board, the pocket-screw holes face the wall and are not seen. The next face frame I make for a cabinet such as the vanity unit will be done with pocket-hole joinery, not with biscuits. The pocket holes will be hidden inside the cabinet.The chalk board shown to the right is made with pocket-hole joinery. Basically it consists of two hinged frames each made up of two legs and an upper and middle rail. The rails are attached to the legs with two pocket-hole screws per joint. The rails for the front frame are drilled on their outside face. The green board and the surrounding moulding hide the pocket holes. The rails for the back frame are drilled on their inside face. The pocket holes are not immediately obvious but it does not take long before you notice them. But there is a way to make these holes ‘disappear’. You can buy a variety of hardwood and plastic plugs to fill these holes.
A much bigger writing surface.
The marketing literature states “Simply glue the plug in the hole and trim with a chisel.” I find that it helps to seat the plugs if a little bit of clamping pressure is applied. You could trim the plugs with a chisel, a block plane or a sanding block.
Seating the plugs.
If you own a router, you have a very accurate trimming tool – use it! Grab a piece of scrap plywood, Masonite or MDF (anything from 3mm thick to 16mm thick will work) and cut a window in it and clamp it to the workpiece as shown here. For some reason, this photo reminds me of an operating theatre and a cloth draped around the surgeon’s proposed operating site. Chuck a straight bit in your router (anywhere between 10mm and 16mm in diameter is a good size).
Ready to trim.
Place the router over the window and plunge till the bit just touches the rail. Back off a fraction (0,1mm – the thickness of photocopy paper) and set the depth rod to plunge to this depth. Plug in the router (you weren’t making adjustments with it plugged in were you?), place it over the window, plunge to the preset depth and trim the excess plug material away. The result of the router trimming is shown here.
If you are worried about running the router bit into the window piece, install a guide bush in the router base. This will prevent overshooting. A light sanding and a coat or three of sealer gives the final result proudly displayed to the right.Now that you know how to ‘dress up’ pocket holes, I’m sure you will make more use of your pocket-hole jig. I have seen furniture designs where plugged pocket holes are used as a feature – elliptical inlays.
A lot better.
By Denis Lock