Burr Elm Table
Tuesday 20 December 2011
Kevin Ley reveals how he made one of his show pieces
After selling all my display pieces in a successful season last summer, I now needed to produce some more for next summer’s shows. My unique selling points are my bespoke designs, and the wood I select, so I wanted to create an unusual design in a suitable timber.
Burr elm has always been a favourite of mine, making unusual and eye-catching pieces that have always attracted attention, sold well and brought in potential clients.
Unfortunately, it is very difficult to find these days and I have nearly finished the stock in my timber store.
I rummaged through and found a few pieces from the same log with a high proportion of sapwood, but very good figuring right through the heart and sapwood.
However, there were several pieces of in-growing bark and dead knots as well as other faults.
I had left these pieces for about 15 years in the store thinking that one day I would find a way of using the sound parts and incorporating the sapwood into a design. This was the day!
I laid out the pieces and had a good think. Some pieces could be joined together with sapwood on both outside edges and heartwood in the centre. There was just enough to make a small coffee table. The top could be finished with breadboard ends to complete the line of sapwood round the outside.
There was not even enough leftover to make stretchers for the legs, but I found a small segment of burr that was an ideal shape to be cut into brackets to brace the legs.
I decided to keep the natural edge of the timber (as I have done on some bowls and cheese boards in the past) and lightly flame it with a blow torch to give a nice contrast to the edges.
I was pleased with the design - it came from the wood and maximised its unusual characteristics. There would be some opportunities for interesting challenges during the construction.
I marked and cut out the timber carefully, avoiding faults where possible and selecting the best faces to be on view. All the pieces were cut a little oversize then faced, thicknessed, and sticked and stacked in the workshop.
There were a couple of pieces of dead in-grown bark on the underside of the pieces destined for the top. Fortunately they did not go right through to the upper face so I decided to remove the bark and fill the holes with burr inserts cut from scrap.
To do this the hole was enlarged slightly and the edges softened using a router following a cut-out pattern with a guide bush.
A piece of acetate sheet was laid over the hole and a suitable shape drawn on, allowing an offset for the guidebush.
This was transferred to a piece of hardboard and the hole cut with a jig saw and finished with a round file.
The pattern was used to route out the bark hole and then used to route another hole in a piece of hardboard. This second hole is an exact copy of the new bark hole‚ and was used to mark a suitable piece of burr as an insert.
This was cut out (slightly over-size) on the bandsaw, shaped carefully with chisels and planes, glued up, tapped into the hole, and planed flush. It was not a perfect match but as it was on the underside of the top it was quite acceptable.
The two main pieces for the top were trimmed to exact size and butt jointed together. The wild grain in burr can mean that short grain is glued to short grain, weakening the joint. As a precaution against this weakness, I reinforced the joint with biscuits.
The natural edge made it difficult to clamp up without damaging the edge so I packed the clamp jaws with a hard upholstery foam. I still could not get a lot of pressure on the joint but I had hand planed the edges particularly carefully so not much was required.
Breadboard ends are used to cover end grain and brace across the grain to prevent cupping, in particular on old- fashioned breadboards, hence the name. However, as the seasonal movement of woods is across the grain and not along it, care must be taken in how they are attached. On breadboards they are usually on a tight, but not glued, tongue and groove, fixed in the centre with a glued dowel or a screw, where there is no relative movement.
I adopted the same principles using two glued dominoes at the centre, dry biscuits on the outer edges to locate the ends and prevent cupping of the top, with double countersunk pocket screws, to allow movement, along the whole of the edge to pull the ends up tight.
The joint was clamped at the centre, again packing the clamp jaws with hard foam, to push the glued dominoes home while the rest of the joint was pulled up by the pocket screws. The double countersinking of the pocket screw holes allows for seasonal movement while still keeping the joint tight.
Plugging the pockets
I had used my Trend pocket screw jig to cut the pockets, and now used the Trend pocket plug cutter to cut suitable plugs from scrap, matching the colour of the area to be plugged. These were glued and tapped into place, trimmed with a flush cutting saw and then sanded.
Shaping the ends
With the ends fixed, I now trimmed and shaped the corners to mimic a natural edge between the ends and the sides of the top. I used a jigsaw, round Surform file and abrasive sheet glued to a dowel to create a natural shape corresponding to that of the sides. The difference in colour would be masked by the flaming.
Legs & feet
The legs were made in a similar way to the top but without the breadboard ends. A cut out - again mimicking the natural edge - on the bottom of the legs, formed the feet.
This was done with a jigsaw and finished with a small drum sander. Biscuit slots and screw pockets were cut in the top of the legs for the joint to the table top.The screw pockets were placed so that they would be covered by the brackets.
The two flat sides of a segment of burr were planed to a true right angle on the surfacer. Cuts were then made on the bandsaw, through the segment, to form triangular pieces with two flat edges at right angles, and the hypotenuse with a natural edge.
Biscuit slots were cut on the square edges to correspond with the slots in the legs. (See step 26).
Preparation for finishing
All the table was now belt and orbital power-sanded down to 150 grit. The natural edges were power-brushed with a flap abrasive brush to remove any loose matter, and bits of bark were picked at and removed with an awl.
All the natural edges were then flamed with a blowtorch. Blowtorches and wood workshops do not mix well, and I took great care to make sure the workshop was clean. (No sawdust or shavings about.) All cans and bottles were sealed and stored, and the fire extinguisher was serviceable and handy. On the bench I had a spray container of water to douse as I went along. The blowtorch was played along the edge until the colour changed, and if sparks started, the water spray was used. Once it was dry, the edge was wire-brushed to remove any loose charcoal.
Next all pin knots and other faults were filled. I use proprietary fillers and adjust the colour with earth pigments if necessary. A cheap plastic artist’s palette is used for mixing and palette knives used to press the filler home. It is relatively easy to get a good result on burr - it already has plenty of variation of colour, grain, and figure, so any filling can be blended in. It is far more difficult to hide a filled fault on a plain wood. It is usually best to make any filled areas slightly darker than their surroundings. The filler was packed in and left a little proud of the surface and, once thoroughly dry, it was sanded flush.
Biscuit slots were cut in the top to correspond with the slots in the brackets and leg tops. The top was placed upside down on padded battens on the bench and glue was applied to the biscuits and slots in the first leg end.
Thiis was then offered up to the top, pushed home, and lightly clamped in position at right angles to the top - this was checked with a large roofer’s square. The screws were driven home in the pockets to pull the joint up. The second leg was fitted in the same way. Once the glue had set the biscuits and slots for the brackets were glued up, the brackets pushed home, lightly clamped in place and left to set.
First, I used a wax filler stick to fill any smaller defects, which were rubbed off as I went along. Now, the burr was very absorbent in places and not so in others. To make sure the porous areas filled up, I applied Liberon finishing oil, diluted 50/50 with white spirit and applied very generously until the wood would take no more. It was left for about 20 minutes, vigorously rubbed off with absorbent cloth and left to dry.
Careful inspection the next day found some dull spots on the surface, mainly on the filled areas and where the grain was so wild that there was some end grain on the top surface. These dull spots in an oiled finish don’t show up until the first coat is applied and can be a real pain to deal with - but I had a plan!
Liberon have introduced a new water-based work top finish and seal that can be applied to previously oiled wood and is ready to sand in 30 minutes. I applied some with a small paintbrush to the dull spots and end grain and, 30 minutes later, lightly sanded it down to the same finish as the surrounding areas. It worked perfectly as a sort of grain filler and sealer. Another useful weapon in the armoury!
Several further coats of undiluted oil were applied at 12-hour intervals until the right finish was achieved. The sapwood lost its white glare and turned a golden colour, blending nicely with the heartwood. It was left for a few days and given a final buffing.
I really enjoyed making this piece out of timber I had been meaning to do something with for so many years. It came together nicely, once I had thought it out, and it did give some interesting little challenges in the making. Its life as a display piece was short though - it sold on its first outing. I must have underpriced it!