Putting Joints into Practice archive

Monday 5 September 2011

John Bullar's simple table shows how he applies his knowledge of joints

Error loading Partial View script (file: ~/Views/MacroPartials/cwsGalleryImages.cshtml)

This article describes an exercise in the practical application of joints. I will look at how two straightforward joints, both cut with power tools, can be used to make a down-to-earth piece of furniture - a small table for the garden or conservatory.

We all have different workshops and different tools we like to use, so I will try to cover a number of options at each stage. The construction is more straightforward than it looks. The corner joints for the legs are half-blind dovetails cut with a router jig. Butt end joints hold the top together and for these you can use biscuits, dominos or dowels.

The wood is just three ready-prepared boards, so there is no planing to be done and practically zero waste - I used treated decking planks to match a platform in the garden. Although the legs are thin they are in pairs at right angles, so the finished table is sturdy.

Cutting to length

Step 1

Start by laying out your boards on a flat benchtop to mark off the lengths. Also, check they are straight and not bowed, cupped or twisted. Ideally this will have been done before leaving the suppliers, but it is worth checking again in case they have moved with drying. The overall length of each board I used was 2.4 metres

Step 2

Having marked the length, draw a pencil line with a square

across one face and one edge of each board, then cut along

it with a sharp panel saw. Alternatively, use a slide mitre saw

or a saw bench. A handheld circular saw could be used with

a crosscut guide, but not a jigsaw because it will not produce

cuts that are straight and level enough

Checking the layout

Step 3

I don’t like to rely on measurements alone because I find it too easy to misread numbers on the measure, or mix them up in my head. For that reason I always apply a ‘sanity check’ and lay pieces of wood together as each one is cut. Any discrepancies between them should then be obvious, and I can stop and sort things out before too much damage is done

Step 4

Once you are satisfied with the lengths, lay out all the boards in neat piles to make sure they match and you have the right numbers of each. There should be four legs, four outer and four inner tabletop boards, and four lower shelf boards

Step 5

The tabletop is made from two matching rotating patterns, one outside the other. There is a small gap between the patterns and a hole in the table centre, which could take a brolly, but the exact dimensions are not important, so long as all the parts fit tightly together

Step 6

As well as providing a surface, the lower shelf braces the legs and stops the table from buckling. You could make the lower shelf match the top but on the table I made, it consists of only the outer rotating pattern of horizontal boards. The length of the lower boards is slightly shorter than the top ones by one leg’s thickness. This is because the lower ones butt up against the inside face of the legs, whereas the top boards form a joint that passes through the thickness of the leg

Prepare router joints

Step 7

When you are choosing the ends to make the router joints, avoid the knots, especially large ones or loose ones. Softwood, like the cheap fir sold for garden work, tends to have a lot of knots, and these won’t cut cleanly with a router and won’t glue well

Step 8

The joints that connect the legs to the tabletop corners are cut with a router. The router itself needs precision guidance for this job so it is fitted with a guide collar on its base, through which the cutter protrudes. Collars come in various shapes and fittings but the size must match the jig it is used with. The router cutter itself is tapered so it makes a slot that is deeper at the bottom and this will form the socket between dovetail joints. Adjusting the cutter depth needs a lot of care so it cannot foul on the collar

Step 9

The router jig has a set of metal fingers like a large comb. This is designed to guide the router cutter as it passes in and out of the wood, forming a series of sockets between dovetails

Step 10

On some dovetail jigs, such as the one I am using here, the fingers are adjustable in position, allowing you to vary the spacing between dovetails. This feature is nice to have - I used it to line up the spacing of the joint with the pattern on top of the wooden boards. However, this is by no means essential and a fixed comb router jig can make good, sturdy dovetail joints

Cutting router joints

Step 11

Different router jigs work in slightly different ways. Some will cut both halves of the joint at once while others, like the one shown, do one half at a time. Here, the wood which will form the edge of the tabletop is clamped horizontally with its face side down, while the half-blind (closed ended) sockets are routed in its underside

Step 12

The wood that will form the legs is clamped with its outer face turned inwards for the second stage while cutting the dovetails themselves. This time the wood is clamped vertically and the template turned over as described in the router jig manual. There is no change to the depth setting of the router cutter, so both sides of the joint will match in depth

Step 13

I have got myself into the habit of test fitting each joint as I make it. That way if there was a mistake in the set-up, I would hopefully spot it early and minimise the wasted time and materials

Step 14

Each of the boards forming the outer pattern of the tabletop will be butt-jointed against the edge of the next board. The butt joint is positioned so that with the dovetail fitted, the outer edge of the butt joint will just align with the inner face of the leg

Step 15

The corresponding sides of each butt joint are numbered to record which will fit which. Pairs of alignment marks are drawn across both sides of each joint, ready to use with a power jointing tool

Step 16

Perhaps the most familiar power jointing tool is the biscuit jointer. With careful use, its joints are sturdy and reliable. The best biscuit jointers are expensive but there are a lot of moderately priced ones too. An alternative is the Domino jointer, which makes mortises for use with its own longer, thicker type of biscuit. Admittedly, they are stronger than biscuits but these machines are always on the expensive side. The third option here is to use a line of dowels. You can bore the holes with a dowelling jointer, or a dowelling jig. Alternatively, you can just use cheap, simple centre markers known as ‘dowel points’, followed by careful drilling

Step 17

When you use a power jointing tool, the wood needs to be firmly clamped to a secure bench. This allows you to press the tool tightly against it so it cannot slip or vibrate while the socket is being cut

Assembling the table

Step 18

The butt joints are assembled and glued-up, starting from the inside of the tabletop and working outwards. Use the best quality waterproof PVA, and don’t forget to line each joint socket fully with glue. Also, apply glue evenly across the end grain before closing the joint. Old woodworking books often tell you that gluing end grain forms weak joints but with the best modern glues this is not true, as I demonstrated earlier in this series

Step 19

It is important that all the joints are clamped firmly together while the glue sets. Exactly how you arrange this depends on how many clamps you can lay your hands on and what type they are. If necessary, you can glue the tabletop up in small stages with just one or two clamps

Step 20

The constructed table is complete and ready to use. Although the wood is pre-treated, it will benefit from a couple of coats of wood-preservative stain


Tegan Foley

Tagged In:

Joints , John Bullar , woodworking , simple table

Diagrams Click an image to enlarge