Preparation of timber

Dressing timber

Timber bought from a retail outlet is normally DAR (dressed all round); this means that it has been through a machine that accurately planes all four sides. This makes the faces and sides relatively accurate but the timber should still be checked before marking out for a project in case there is any warping of the timber. If the width or thickness has to be reduced, first establish an accurate side or edge then mark it so that you have a datum side/edge to measure from.

Thicknessing

The thicknesser

This machine is used to reduce the thickness of a board by feeding it under a set of rapidly rotating planer blades. The thicknesser is an excessive sound polluter; therefore, anyone in close proximity will need ear protection. There are board length and edge use restrictions and teacher permission is required for its use .

Why face side and face edge?

Modern timber is machined to a high degree of accuracy but this was not always the case. Even now, a length of timber might have one edge which has been cut straight and another which still retains the outside shape of the tree - known as a Waney Edge.

Good practice when marking out timber therefore is to choose the straightest edge and mark this as the Face Edge. Similarly, select the best or flattest surface and mark this as the Face Side as shown. Throughout any subsequent marking and measuring, the Face Side and Face Edge are used as the Datum Surfaces from which all measurements are taken and against which the stock of a tool such as a Try Square or Marking Gauge is pressed.

Note: Even when Squaring Round (i.e. marking a line all around a piece of timber) a Try Square stock should always be pressed against either the Face Side or Face Edge.

Marking out and checking angles

Accuracy is vital when marking out and checking angles. If you do not measure and mark with precision, and then cut carefully to your marks, the parts will not fit together neatly, your work will be out of square and the joints will not hold securely.

The pencil versus the marking knife

A sharp 2B grade pencil can be a very useful implement - as long as it is kept sharp. If blunt, the pencil line can be 2 mm thick and, therefore, inaccurate . A carpenter's pencil has a wide, and therefore stronger, writing edge, which makes it ideal for use on rough timber.

A sharp marking knife is used to mark across grain. This cuts the fibres and allows a chisel to sit in the groove to accurately finish cutting a joint. It also prevents a saw tearing the fibres.

Correct use of the marking knife

Measuring rules and the straight edge

Quality steel rules are available in 300, 600 and 1000 mm sizes and, although flexible, may be used on their edge to test for a flat surface. Wooden or plastic folding rules are ideal to avoid carrying a long rule around but a retractable tape measure is far more useful and comes in lengths of two metres or longer. The straight edge is less flexible and is ideal for test ing flat surfaces- especially if using its thinner splayed edge.

Try squares

A try square consists of a stock attached to a rectangular high carbon steel blade , generally by rivets. The stock is normally made of a fine, straight-grained and stable timber like beech with a brass rubbing (wear) strip attached to the inner edge. A stock can also be plastic or cast iron. The try square is available with blade lengths from 100 to 300 mm, and both the inner and outer edges of the blade may be used.

It is an accurate tool and should be treated with care. When using the try square for marking perpendicular lines (squaring), hold the timber against the stock with the thumb,

use the index finger to press the blade flat on the timber and the other fingers to push the stock against the timber. Use a sharp 2B pencil or a marking knife to mark the surface depending on what you are marking. When checking with the try square always hold the stock of the square firmly against the timber with the blade just clear of the 90° angle to be checked. While keeping the stock against the timber, slide it towards the angle to be checked by resting it in position rather than pressing it.

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