Working with templates in intarsia

What a template does

A template turns a drawing into a repeatable shape. Instead of marking out each piece afresh, the shape is fixed precisely once and then transferred, guided or cut. In intarsia there are four kinds of template for this, which do not exclude each other but often work together in the same piece:

• Paper pattern: a printout of the cutting lines that is stuck onto the veneer and cut with it. It is used once and quick to make. How patterns are prepared, printed and transferred with registration marks is covered in designing and transferring an intarsia.
• Cutting template: a rigid plate whose edge the knife runs along. It turns one shape into a series of identical pieces.
• Assembly jig: a board with stops that fixes where each piece lies. It does not set the shape but the position, and stops a pattern from shifting as it is put together.
• File: a vector drawing for a laser or cutting plotter. Here the drawing itself is the tool, and its accuracy goes straight into the wood.

When a template pays off

A rigid template costs time before the first piece is cut. It pays off when the same shape comes up often enough:

• Repeated elements in a pattern: a geometric pattern of triangles, diamonds or cells often consists of a few basic shapes that appear dozens of times. Every difference between two pieces that should be the same shows at the joint.
• Small series: an object made several times should look the same every time. Without a template, that depends on how the day is going (making small objects).
• One motif in several pairings of wood: when the shape stays the same and only the woods change, the template is what makes the variants comparable.

Photo: Reihax

A one-off piece whose parts follow the wood, on the other hand, needs no rigid template: a wall piece in which every area is cut to the grain and colour of the sheet, or a piece meant to be laid around a knot. Here the paper pattern is the better choice, because it follows the sheet and not the other way round (intarsia wall art).

Making a cutting template

A cutting template is only as accurate as its edge. The material has to be hard enough for the blade to slide along it instead of cutting into it, and thin enough for the knife to lie flat against it.

• Material: acrylic of 2 to 4 millimetres, laminate, hardboard with a sealed edge or thin aluminium. Acrylic has the advantage that you can see the veneer and its grain through the template. MDF and card are fine for trial pieces, not for series.
• Making it: the most accurate template is one that is itself lasered or milled, from the same file as the pattern. By hand it is filed and sanded against the drawing until it agrees with the calipers.
• Do not take it from the first piece: a template copied from a cut piece takes over that piece's errors and adds its own. The template comes from the drawing.
• Label it: every template needs a name or number, an arrow for the grain direction, a mark for the show face and the date or version. An asymmetric shape turned over by mistake gives a mirrored piece.

Cutting against the template

The template lies on the piece, not on the waste. That protects the side of the veneer you want to keep, and if the knife slips, it runs into the waste. So that the template does not wander, it is held with double-sided tape, a non-slip film or light pressure. The tape must leave no residue on the veneer that would later interfere with the glue.

The blade lies flat against the edge and stands upright. If it tilts, the piece comes out wider or narrower at the bottom than at the top, and the joint opens after pressing. Cut in several light strokes rather than one hard one; the first stroke only scores, the following ones separate. With brittle woods such as wenge, cut across the grain first and then along it, so that the corners do not tear out. More on blades, the order of cuts and edges is in cutting and fitting veneer.

Why template errors add up

An error made in cutting freehand is random: one piece is a little too big, the next a little too small, and much of it evens out. An error in the template is systematic. If it is 0.1 millimetres too wide, so are all the pieces, and in a row of ten pieces that becomes a millimetre. How such deviations travel across a pattern and how to recognise them is described in the section on cumulative offset in assembling an intarsia.

That is why a new template is tested with a trial piece before the series begins: cut a few pieces, lay them together dry and measure them against the drawing. Only when the trial agrees across its whole width is the template approved.

The file as a template

With a laser or cutting plotter, the file is the template. It does not wear, but it has its own sources of error. The laser burns away a narrow gap, the kerf. If it is not allowed for, every piece loses half its width at every edge, and a gap is left between two pieces. How wide the kerf is depends on the machine, the power and the species, so it is found with a test cut in the actual veneer and compensated in the file. Then there is the browned edge, which stays visible on light woods (laser and knife cuts compared).

Reihax uses laser technology where it supports precision; assembling the pieces stays handwork (about Reihax). Then especially the file gets the same care as a rigid template. It carries a version, is checked with a test cut after every change, and the version that was good is not overwritten.

Photo: Reihax

Wear, checking and storage

Every rigid template wears. The blade presses small nicks into the edge, corners round off, and soft material gets thinner where it is used most. The treacherous part is that the wear happens slowly, and every piece looks fine on its own. It only shows when pieces from different months lie side by side.

• Check: before every new series and whenever a piece does not fit; against the drawing or the file, with calipers, a straightedge and raking light along the edge.
• Replace rather than rework: a template with nicks is made again. If you file it, it gets smaller, and so do all the pieces.
• Store: flat, clean and apart from tools that can scratch it; acrylic in paper or a sleeve. The templates of one pattern belong together in a folder, with a sheet showing which pieces come from them and how many.

Checklist for working with templates

• Template made from the drawing or file, not taken from a piece
• A hard, straight, smooth edge; dimensions checked with calipers
• Name or number, grain arrow, show face and version on the template
• Trial piece cut and measured dry against the drawing
• Template lies on the piece, not the waste, and is secured against slipping
• Blade flat against the edge, upright, in several light strokes
• For files: kerf found in the actual veneer and compensated
• Checked for nicks, rounded corners and deviation in size before every series