12. Timber

Types and suitability - What to look for when purchasing - Seasoning, cutting out, storing

I can well remember my first approach to woodturning, and the subsequent visit to the timber yard in search of a few suitable pieces of wood. All I knew was that I wanted some hardwood suitable for turning and that it had to be well seasoned. To me, at that time, it all looked alike, but after buying lots of useless pieces, I soon formed my own opinion about turning requirements; perhaps you learn a lot quicker by your mistakes. I certainly did. One big advantage of woodturning is that we need not have the wood prepared for us, and all sorts of off-cuts can be put to good use.

Practically any hardwood is suitable for turning, in particular maple, sycamore, walnut, beech, oak or any other hardwood with close and beautiful grain.

Walnut is, perhaps, one of the most used timbers in turning as it answers all the necessary requirements in appearance and texture, and it is sweet to turn and easy to polish. A simple wax polish will quickly give a really beautiful finish.

Oak, on the other hand, can be quite tricky to handle and the various species vary a lot in texture. American oak works and finishes well, but the pinkish colouring is sometimes difficult to match up. English oak is very hard and finishes well but sometimes it is rather open grained and requires quite a lot of filling. It lends itself very well to fuming with ammonia, but it is difficult to colour with some stains. In my opinion, water stain is the most effective. If a rich brown tint is required (I call it church brown), then immerse the turning in a bowl of strong caustic soda for twenty-four hours, and it will come out looking 200 years old!

Sycamore, beech and maple all turn very well, with lovely long shavings coming away from your gouge and chisel. Sycamore and beech will probably require staining as they are so light in colour, but maple is best left natural.

You may have timber offered to you which has been kiln dried; that is, the timber is cut to different thicknesses and stacked in a heated room, for a predetermined period, the object being to drive out the moisture and sap by prolonged gradual heat. From time to time the timber in the kiln is checked for moisture content, and when it has dropped to the desired level, the wood is removed and stacked outside in the air. Some kilns are not operated properly and the wood is spoiled, although externally the wood appears to be all right. However, in cutting into a
2          in. square, for example, you will probably find quite large splits right in the centre of the wood.
For this reason, I prefer to use air-dried timber and although the seasoning period is much longer, the resultant planks of wood are much better. For air drying, the tree is cut up into suitable planks and stacked one above the other, with small sticks in between each plank to allow for air circulation. The drying period is reckoned as being approximately twelve months per inch of thickness, thus a
3          in. plank would take three years. This period can be reduced, if the planks of wood are cut to nearly finishing size, that is, in 2 or 3 in. squares, or 7 × 1 in. boards. When the boards are cut into squares, they are usually stacked in short lengths and these are most suitable for turning table legs, etc. Each stack of squares usually carries the date it was cut up, so it is quite easy to tell when it is properly seasoned. In this case, you can reckon on six months per inch for seasoning time.

To prevent splitting and end shakes during seasoning, the ends of the wood should be painted with tar or wax. I hope this will give you some idea of what to do if you have some freshly sawn timbers of your own to store.

Wet or green timber is much cheaper to buy than that which is already seasoned. Whether or not the piece of wood is fit to be used can usually be determined by its weight and touch. Green timber is heavy for its size and very cold to touch. When buying your wood seasoned, be on the look out for splits on the end, and if there are any this portion should be cut away before you start to turn.

Another thing to look out for is woodworm. This beetle attacks only the sap wood and its presence can soon be seen by the tell-tale holes. You can quite easily recognize the sap wood as its colour is much lighter than that of the rest of the wood. If you have any wood in your shed with woodworm, put it on the fire, as, doubtless you know, this small insect will get into everything else. For this reason, I prefer not to carry too large a stock of timber.

Walnut, although one of the most beautiful of woods, is a very wasteful one to buy, and demands very careful inspection, for the following reason. Walnut trees like a great deal of moisture and running up the centre of the tree is a small hollow tube. This goes all the way to the top of the tree and up every branch, so wherever you cut through the tree, you will see this small pipeline, about the size of a pencil. For this reason, alone, walnut can be extremely wasteful, particularly if you buy a plank that is out of the centre of the tree. I prefer to buy those which are cut about three inches from the centre. As the walnut seasons, splits will radiate from the pipeline, thus making a large area in the centre of the tree quite useless. So, before you buy up all the walnut in your neighbourhood, look very closely at it.

Elm is another wood which looks well and turns reason­ably although the grain will require filling to get a good finish. This wood also has a nasty fault. Some boards, upon inspection, will show a whitish-grey streak in places. This is a very hard gritty substance and will take the edge off all your tools in next to no time. How it gets there, I do not know.

Old table and chair legs can usually be picked up quite cheaply from junk shops and can be turned into some very useful items, but be on the look out for old nails, etc.

If you have a window facing the sun in your shed, keep your stock of timber away from it. Sun will ruin any wood that is underseasoned. Always stack your timber in the shade in a good current of air if you want to avoid splits and shakes.

Short-grained wood should be avoided, if possible. It is quite easily recognizable by the grain running diagonally across the sawn board. For some forms of carpentry this would not matter a lot, but when an article is turned, the grain must run lengthwise reasonably straight, or otherwise the finished article will be weak and easily broken. Also, it will not retain its original shape (see Fig. 20).

The wood required for bowls must be carefully chosen. If the plank of wood you are using was cut from the centre of the tree, then cut your disc of wood from the portion between centre of plank and outside. Avoid using the portion which is the centre of the tree. The bowl is then shaped on the lathe so that the contours of the bowl follow the curvature of the annular rings. Similarly, if a really large bowl is required, then pick a plank which was cut from between centre of the tree and the outside (see Fig. 21) and shape your bowl as before, with the grain of the wood following the shape of the bowl.

Quite often you can purchase ready-cut discs of wood for bowl turning, and the beginner can find it quite a prob­lem to decide which side of the block of wood is to be the outside of the bowl. Take the disc of wood in your hands and, upon inspection, you will notice the annular rings in the end grain. From the shape of these rings, it is an easy matter to determine just whereabout in the tree the block of wood came from. Try and visualize which side of the block of wood was nearest to the centre of the tree and that will be the side to be hollowed out and will be turned last, using normal methods of bowl turning.

Figure 20. Short grained timber.

Figure 21. Method of cutting out bowls to prevent warping and splitting,

From time to time you may be called upon to make circular table tops, or bases for floor standard lamps. These may be anything from 12 in. in diameter. In these projects, do not attempt to turn them out of one large piece of wood. It is much better to make the required size out of two or three pieces glued together. The chances of twisting and warping are reduced to a minimum.

I mentioned in the chapter on faceplate work about turning bowls in wet or green wood. This is also possible for other types of work where you wish to dry the wood out quickly. Turn your article to within about J in. of the finished size, allowing for subsequent twisting during the drying period. After rough turning, it should be put in a hammock of wire netting, hung in an airy position but away from direct sunlight.

Timbers from hot climates, such as mahogany and agba, very often have what is called thunder shakes. It is a very common occurrence in trees of large diameter grown in tropical climates. These thunder shakes are recognizable by short, irregular and broken lines running across the grain of the wood. The sections of timber with this fault are quite useless, except for the turning of small articles, as there is no strength in the wood.

The timber yard and the junk shop are not the only sources for finding suitable wood for turning. I have found very useful lengths of hardwood when I have been walking along the seashore after a good winter gale.

Softwoods are not generally accepted as being suitable for turning but some species of pine will produce very attractive articles, particularly Columbian and pitch pine. To turn these woods, you will require very sharp tools.

When we inquire at the timber yard for the price of certain species of wood, we are usually quoted the price as per cubic foot and this can be quite misleading, particularly if it is to be 3 in. square stuff. If, for example, a piece of wood is quoted at $2.40 per cubic foot, that means a piece 12 in. long, 12 in. wide and 12 in. deep. Therefore, a piece 12 in. x 1 in. will cost 2O¢ per foot or 1/12 of the cubic foot, about 1.7 cents per square inch per foot. Now, the 3 in. square material you are interested in will cost about I5¢ per foot run. It is quite easy then to work out the price, if you divide 144 into the price per cubic foot of the timber. This will give you the cost per square inch per foot. It is then simple to work out the price for any size by working out how many square inches there are in the required cross-section.

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