MARKING & SCRIBING

In any woodworking job it goes without saying that accurate marking out and scribing of timber is vital if you want to obtain the best results. As a general rule you can get by with the minimum of equipment, which includes a pencil, straight-edge, steel rule, or tape, and marking knife. More accurate tools are available, such as gauges, compasses and dividers, which are a worthwhile investment if you are doing a lot of joinery work.

If you fail to mark out timber correctly, you will end up with poor joints and probably an unstable construction; and if you have to start again, a lot of time and money will have been wasted. So marking and scribing are jobs you must take time and care over.

Of the two basic items, in principle a marking knife is used where precision is all important, such as in cabinet making; a pencil is used for more general carpentry work where such a high degree of accuracy may not be required. A pencil is also used to mark waste areas of timber which have to be removed and also to identify the face side and edge of timber.

MARKING KNIFE

This tool consists of an angled steel blade, which is ground and sharpened on one side only. When marking, the knife is held with the flat side of the blade against a metal straight-edge, which can be the blade of a try square or a steel rule. The cut the knife makes in the timber being worked will help prevent a saw or chisel splintering the work when cutting through.

The knife is suitable for marking the cutting lines on veneered surfaces. By sawing along scored lines you will be far less likely to tear the veneered surface; but because the scored lines are quite difficult to see, it is a good idea to go over them with a pencil so they show up quite clearly.

MULTI-BLADE KNIFE

Multi-blade knives for marking are also available; these are particularly useful since you can fit the relevant blade for the work involved. You can buy these knives with either fixed or retractable blade fittings. A range of blades is available for different types of work.

NORMAL DUTY

A general purpose blade for marking out wood, trimming leather and suede and cutting paper, card and polystyrene tiles. HEAVY DUTY Used for scraping off’ paint or varnish and cutting plastic, flooring tiles and roofing felt.

HOOKED

Ideal for cutting vinyl and textiles. ANGLED Used for scoring long lines on timber and plastic and for cutting card. It can also be used for routing and cutting carpet, roofing felt and vinyl. Concave Will cut carpet, roofing felt and vinyl. Also used for routing.

CONVEX Especially useful for cutting wallpaper; will also score most materials and cut carpet. LAMINATE Designed especially to score laminate.

WARNING

Inaccurately scored lines cannot be removed. Until you are confident you can get it right first time, it is wise to set out the cutting lines on the timber to be worked with a pencil first.

These can always be removed with a rubber or fine glasspaper. When you have checked for accuracy, you can score over the pencil marks.

PENCIL

When marking timber, don’t be tempted to pick up and use the first pencil stub which comes to hand. The pencil should be of a reasonable length so you can hold it comfortably for precise marking. It should be sharpened to a chisel point so you get clean, fine lines. For most work an HB grade pencil is suitable; this is hard enough to retain its point for some time, while soft enough not to damage the surface of the work. Use an even softer grade pencil, such as a 2B, if the timber is very soft or if you are just lightly marking the work for accuracy prior to using a marking knife. Use a harder grade pencil, such as an H or 2H, for fine marking where a marking knife is not available and where hard-surfaced timber is being worked.

For general marking of waste areas and with heavy work, it is best to use a carpenter’s pencil, which has a wide rectangular lead available in soft, medium and hard grades. The medium grade is suitable for most work. The lead should be sharpened with a sharp knife and the end scraped to a chisel edge. If it wears down while working, you can rub it against medium glasspaper held on a flat work surface to renew the edge.

Gauges

Woodworkers’ gauges are the most accurate tools to use when scribing or cutting lines in timber; their one limitation is that they can only be used to scribe or cut lines parallel to the edge or end of timber. To mark out curves and circles you will need a pair of compasses or – for larger areas – a timber lath, trammel heads or large blackboard-type compasses.

SINGLE POINT The most widely used type is the single point marking gauge, the stem of which has a hardened steel point that protrudes about 3mm from it at one end. A stock slides along the stem and is held in place with a thumbscrew. To set the gauge, position the stock at the approximate dimension required, then partially tighten the thumbscrew and tap the end of the stem gently on the bench until the point is the required distance from the stock, which can be checked with a rule. To mark the timber, grip the gauge with your thumb and first finger round the stock and your other fingers on the stem and run the gauge down the timber: keep the point at an angle to the work and the stock firmly against the edge of the work. Score lightly several times, allowing the point to mark a little deeper each time until the line can be seen clearly. If the gauge is not held firmly to the work, it can wander and follow the grain of the timber and you will not get an accurate parallel line. Always mark out with the stock on the face side of the work.

Keep the point sharp by using a small oilstone whenever necessary; when the gauge is not in use, slide the stock up to the point to protect it. CUTTING

This gauge is similar to the marking gauge, except that it has a blade instead of a point – and this is held in place by a wedge. Use it like the marking gauge when cutting through thin materials such as veneers, light plywood, card and thin plastic. Use the gauge on each side of the material until the cuts meet. A cutting gauge can also be used to mark out timber across the grain, since it cuts into the work and will therefore not tear the grain.

MORTISE

This has two points and a sliding stock. The gauge is used to set out the parallel lines when making mortise and tenon joints. The method of using this gauge has already been covered in the Course.

When a gauge is not available, a pencil and rule used carefully in conjunction with a try square can help you draw reasonably parallel lines. Hold the rule firmly in one hand with your thumb on the required measurement and your fingers steadying the rule underneath and touching the edge of the work. The end of the rule acts as a guide for your pencil. Check with a try square to make sure the line is parallel.

COMPASSES

Ordinary pencil compasses can be used to mark small radius curves and circles on timber. The legs are first set to the required distance apart and the point of the compasses is then placed at the centre of the circle; the leg holding the pencil is swung carefully round several times to mark out the curve or circle.

WING COMPASSES

These are suitable for more accurate marking. One leg has a point and the other is flattened and sharpened so it scores the surface of the timber as it is moved. This helps to ensure a clean edge when cutting with a saw or chisel.

TIMBER LATH

This is useful for marking out larger circles. A nail or pin is driven in near one end of the lath to act as a pivot and a pencil is held in a notch or hole near the opposite end at the required distance from the nail for the radius to be marked on the work.

TRAMMEL HEADS

For really accurate marking of large curves or circles, trammel heads mounted on a timber beam should be used. Both heads are pointed for scribing and one usually has a socket so a pencil can be fitted. This apparatus is used in a similar way to compasses; place one point at the centre of the circle and move the other point to mark the required radius. WING DIVIDERS With points on both legs, these are used for stepping out equal distances along a length of timber. They can also be used to scribe a line along a length of timber when it is necessary to fit this to an irregular surface; the outline is transferred from the irregular surface onto the timber to be fitted.

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