JC Wood Technology flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Fibre saturation point

The moisture content at which all cell-wall water is present but no free water remains in the lumens, about 28–30%; above it wood neither shrinks nor swells.

Compression wood

Reaction wood formed on the underside of leaning softwood stems; it has high lignin content, is darker and brittle, and shrinks far more along the grain than normal wood.

Equilibrium moisture content

The moisture content at which wood neither gains nor loses moisture to the surrounding air, set by temperature and relative humidity; about 12% at 20 °C and 65% RH.

Sorption hysteresis

The effect where, at the same relative humidity, wood that has been drying holds a higher equilibrium moisture content than wood that has been wetting up.

Ring-porous hardwood

A hardwood with large earlywood vessels forming a distinct ring and much smaller latewood pores, such as oak, ash and elm; it gives strong visual grain.

Encased knot

A knot surrounded by bark or resin and formed by a dead branch; it is not bonded to the surrounding wood, so it is loose and downgrades the timber.

Use class (EN 335)

The classification of the biological hazard a timber component will face, from UC1 interior dry to UC5 marine, used to set the required durability and preservative treatment.

Quartersawn timber

Timber sawn so that growth rings meet the face at 60–90°; it is more dimensionally stable, less prone to cupping and shows medullary-ray figure on oak.

Micro-bevel

A small secondary bevel, usually 5° steeper than the primary bevel, honed at the cutting edge; it speeds honing and strengthens the edge without regrinding the whole bevel.

Cap iron

The chip breaker fitted over a bench plane iron, set 0.3–1 mm back from the edge and seated flush; it turns the shaving and reduces tear-out on difficult grain.

Saw set

The sideways offset given to saw teeth, alternately left and right, which makes the kerf wider than the blade plate so the saw does not bind.

Fleam

The angle at which the file is held across a saw blade when sharpening crosscut teeth, typically 60–75°; rip teeth are filed square with 0° fleam.

Riving knife

A steel plate mounted behind a circular saw blade that rises and falls with it, keeping the kerf open and preventing stock from closing onto the blade.

Kickback

Sudden ejection of the workpiece back toward the operator when the blade binds or the work lifts off the table, prevented by a riving knife, short fence and push sticks.

Climb cut

Routing or sawing with the cutter rotation rather than against it; it gives a cleaner edge but pulls the work forward, so it is used only for light finishing passes.

ATB saw blade

Alternate top bevel: a tooth pattern in which the top bevel alternates left and right, shearing the fibres and giving clean cuts in crosscut work and sheet material.

Haunched mortise and tenon

A tenon with a short extension above the main tenon that fills a groove in the stile, used in doors so the tenon does not weaken the glazing rebate.

Housing joint

A groove cut across the face of one member to take the full width of another, locating shelves and dividers and resisting racking in carcass construction.

Face side and face edge

Two adjacent jointed surfaces marked with the F/S and F/E symbols; every subsequent setting-out measurement is taken from these reference faces.

Barefaced tenon

A tenon with a shoulder on one side only, used where a rail is set back from the face of the stile so the outer faces finish flush.

D4 adhesive

The highest EN 204 durability class for PVA-type adhesives, for joints exposed to frequent wetting; it passes the most severe boiling-water test in the standard.

Stearated abrasive

Abrasive paper coated with zinc stearate soap to resist clogging when sanding finishes, paint and resinous timber; it is not intended for heavy bare-wood stock removal.

Sanding sealer

A thin, fast-drying first coat that stiffens raised fibres so they can be sanded off, reducing the number of finishing coats needed to fill the grain.

Borate preservative

Water-borne boron salts that diffuse into timber and protect against insect and fungal attack; they leach readily, so use is confined to interior, protected applications.

First-angle projection

A drawing convention in which the object lies between the observer and the projection plane, so the view from above is drawn below the elevation; standard in Europe.

Cutting list

A schedule giving every component's finished size, material, quantity and grain direction, used to plan machining and to calculate the bill of materials.

Datum dimensioning

Taking all dimensions from one common reference face or line instead of chaining them end to end, so small errors do not accumulate across the work.

Local exhaust ventilation

Extraction hoods and ducting fitted at the machine that capture dust and vapour at source, keeping airborne exposure below the workplace exposure limit.

Workplace exposure limit

The maximum permitted concentration of an airborne hazard such as hardwood dust, expressed as a time-weighted average over an 8-hour reference period.

NVR switch

A no-volt release switch that stops the machine when the power supply is interrupted and will not restart until the operator deliberately presses start.

Chain of custody

Documented tracking of certified timber through every stage from forest to finished product, which allows a valid FSC or PEFC claim to be made.

EUTR due diligence

The EU Timber Regulation requires operators placing timber on the market to record species and harvest origin, assess the risk of illegal sourcing and mitigate it.