Monday 25 January 2010
Colin Simpson visits a local timber yard and shows us what to look for and what to avoid
If you are inexperienced in buying wood, a visit to a timber yard can be quite daunting. Let's face it - wood can be very expensive (as with a piece of snakewood I found). I know that, in the past, I have bought wood that I have been very disappointed with, and I am sure many of you have done the same. This article aims to point out a few of the pitfalls I have fallen into so you can avoid them, and gives a few tips on what to look for when buying timber for use while turning.
Firstly, if you know little about what to look for, I recommend going to a well-established reputable timber yard, preferably one that does some timber conversion. This way there is likely to be a knowledgeable person available to ask.
As you might expect, the more the timber has been worked on before you buy it, the more it is going to cost per cubic foot (cuft) or cubic metre. So a tree trunk will cost less per cuft than the same trunk cut into waney-edged boards. Square-edged planks will cost more than waney-edged boards, and turning blanks are arguably the most expensive way of buying wood. However, there is a trade off. The less the wood has been machined before you buy it, the more you will have to do. That sounds obvious, but you will also need the tools to convert it. Chainsaws and the necessary protective equipment are expensive. You will need a bandsaw to cut bowl blanks and you will generate a considerable pile of waste wood. If you are aiming at selling your work, a proportion of the cost of this equipment and your time must be added to the cost of your pieces. You will have to do the sums for your set-up, but if you are only making a few dozen pieces a year, then buying 'ready made' bowl blanks may well work out as the cheaper option. Besides which, you will be able to try all those different species.
Boards and planks
If you decide to buy a board or plank to cut your own blanks, here are a few things to look out for. Throughout this article I am going to point out some faults in the timber, but it is worth keeping in mind that one person's fault is another one's feature. Faults can be enhanced, filled with contrasting wood, metal, or stone dust. Cracks can be stitched together with wire, leather or staples.
Timbers come in many shapes and sizes, including pieces with very obvious splits and fractures, which are easily visible. This is not necessarily a problem as you may be able to use the timber on each side of the split. However, end checks in boards can be much deeper than you might imagine and you could end up wasting 6 or 7 inches (150-175mm) from each end of the board.
As is the case with the oak board I found, there are still some splits showing in the remainder of the timber, so another slice will need to be cut off before usable timber is reached.
The yew plank I saw appeared to have good wood on both sides but an examination of the back of the board showed the enclosed bark went right the way through the board at an angle. There was also another bark inclusion rendering the board useless for bowls, although there was still some good timber for smaller items. You might be able to negotiate with the timber yard to get a good deal on a board similar to this.
I would recommend staying away from planks of wood that have the pith in. The piece I was had considerable radial checks that went very deep, wasting a lot of wood. There was also a large ring-shake in this board to the left of the pith.
Many woods have a great contrast between the sap and heartwood. The padauk board is a great example and bowls or platters that have some sapwood on their rims can look very striking. If I bought this board I would definitely keep the sapwood. However, in many species the sap can be attacked by worm or other boring insects.
The bubinga board I saw had insect infestation in the sap. I would probably cut this away before using the rest of it.
Spalting or fungal attack can produce striking patterns in the finished pieces, but careful selection is required. I came across super piece of spalted sycamore, it even had some ripple down the left side. Ensure that you examine the spalted area well by digging your thumbnail or small screwdriver into it. If it is soft, it could be difficult to work and finish.
I also saw an ash plank that had a knot at the bottom and a few splits just above it. This area of wood should be discarded, but there was some fantastic figure in the wood above this and it would make a superb bowl. It is sometimes worth discarding some wood to get to the best bits.
I am far less concerned with splits and enclosed bark if I am buying burrs. A piece of pippy oak, for example, had cracks and all. Clearly a salad bowl would be out of the question, but the piece would make a lovely decorative bowl and the cracks could be left or filled with dust.
Logs and trunks
I am not going to show you how to convert trunks here. Please refer back to Woodturning issue 178 for details of how to do this. Here are a few things to look for if you are buying logs:
The pippy elm log I saw had a large split right through the centre. Examine the other end of the log and if the splits are in the same direction, then the log could easily be cut in half to make, for example, two natural-edge bowls. However, I would not attempt to make a hollow form from this log as the splits might cause it to explode. If the splits on the other end do not run in the same direction, I would leave the log for someone else.
Similarly, I also saw a log of box, which at first sight appeared to have similar defects to the previous log. However, closer inspection showed that the 'split' was actually enclosed bark. This log had been cut from a fork of the tree. A close look revealed two piths; one for each branch. Similar bark enclosures and two piths can occur in some trees where two branches join together - yew is a good example of this occurring.
The oak butt I saw measures 680mm (26in) in diameter and clearly needed further conversion. It was a fresh log, so the wood is wet. There was a small split at the pith but this will get bigger if the butt was left. I would need to consider how to convert this butt, taking into account the ring shake seen halfway from the pith and the bark. The ring shake will go further than the bit that is visible and may go right the way round the butt. This is not necessarily a problem but must be taken into account when converting the log.
The hollow elm trunk I saw appeared to have been here for years. Clearly the trunk was of no use for slabbing into boards and perhaps the timber yard didn't know what to do with it. The burrs along its trunk may still be sound and it is worth speaking to the timber yard and making them an offer.
Blanks and squares
Some exotic timbers have import restrictions on them. A loophole in these restrictions means that if the wood has been part-worked or machined, more can be imported. I saw an example of this where squares of anjan from India had had a tenon machined on one end of the timber.
Whilst most of the decisions on where to cut the blanks have already been made, there are still some things to look out for. As with planks and boards, I would normally leave any blank that has the pith in it. Don’t automatically discard blanks that are not perfect. I also saw a blank cut from the edge of a board with the remains of the bark on one side. If you made this the bottom of the bowl, this area will be turned away, so this blank will make a nice shallow ogee-shaped bowl. The bowl may be unbalanced until the back is finished, so you may need to slow the lathe down initially.
There was also a blank with a dead knot in the side and a little rot on the top face. The rot might turn away, if you make this face the bottom, but the dead knot is likely to fall out unless some repairs are done with cyanoacrylate and wood dust. Even if the knot stays put, I don't think it will make a nice feature in this sized bowl. Don't be afraid of sifting through the blanks.
Even if the blanks were cut from the same board, there may well be different features in each one. Look for interesting figure - ripple for example, but don't make the mistake I made many years ago when I thought I was buying a rippled sycamore board only to find out that the 'ripples' were in fact saw cuts!