Assam ASSEB HSLC Wood Craft cheat sheet

Cross-section of a dicot stem, outside in: bark (outer cork + inner phloem), cambium, sapwood, heartwood, pith. Cambium is the only layer producing new cells.

Three planes of section: transverse (cross) shows annual rings and pores; radial runs pith to bark; tangential is tangent to the rings and shows the widest grain figure.

Softwoods (conifers, e.g. pine, fir, deodar) have tracheids only and no vessels; hardwoods (e.g. sal, teak, sissoo, mango, gamari) have vessels (pores) and fibres.

Cell wall layers: middle lamella, primary wall, S1, S2 (thickest, main strength), S3. Microfibrils in S2 are wound at a steep angle to the axis, giving longitudinal stiffness.

Shrinkage order greatest to least: tangential > radial > longitudinal. Tangential shrinkage in many species is roughly twice radial, so flat-sawn boards cup and check more than quarter-sawn.

Density and strength rise as cell-wall thickness and latewood proportion increase; strength is roughly proportional to density at a given moisture content.

Moisture content (MC %) = (wet mass − oven-dry mass) ÷ oven-dry mass × 100. Fibre saturation point is about 28–30% MC; above it no further swelling occurs.

Wood is anisotropic: strength and stiffness are highest along the grain and lowest across it; tension parallel to grain exceeds compression parallel to grain.

Defects: knots (branch bases), shake (ring separation), check (drying crack across rings), and reaction wood - compression wood in softwoods, tension wood in hardwoods.

Rip saw: teeth 4–7 per inch, filed for ripping along the grain. Crosscut saw: 7–12 per inch, bevel teeth severing fibres across the grain.

Set of a saw tooth is the lateral offset that makes the kerf wider than the blade, preventing binding; set alternates left–right.

Jack plane (about 350 mm) for rough work, smoothing plane (about 240 mm) for finishing, block plane for end grain.

Frog adjusts the mouth: a fine mouth (cap iron close to the edge) suits hard, curly timber; a wide mouth suits soft, thick shavings.

Chisel bevel is typically 25° with a 30° micro-bevel; grind on a wheel, hone on a stone, keep the back flat.

Sharpening angle rule: softer wood and paring favour a lower bevel; hard wood and chopping favour a steeper bevel.

Brace and bit: the bit is turned clockwise to bore, counter-clockwise to withdraw; a countersink bit widens the hole mouth for a flush screw head.

Marking-out trio: try square (90°), marking gauge (line parallel to an edge), mortise gauge (two pins set to the chisel width).

Safety rules: never carry a chisel with the edge toward the body, never cut toward the hand, keep the blade covered when not in use, and clamp work before sawing.

Butt joint: end grain to face or edge, held only by glue, nails or dowels; weakest of the common joints.

Housing (dado) joint: a groove across the grain receives a shelf or rail; a stopped housing does not run through the edge.

Mortise and tenon: mortise width equals chisel width; tenon thickness about one-third of the rail thickness; haunch fills the end of a groove.

Dovetail: tails on one member, pins on the other; through dovetails for boxes, lapped dovetails for drawer fronts where the tail shows on the face.

Half-lap and cross-lap: timber removed to half thickness on each member so the faces finish flush; used in frames and grid work.

Finger (comb) joint: interlocking rectangular fingers, usually machine-cut, strong in tension; box (corner) joint with pins and tails resists pull-out.

Dowelling: dowel diameter about one-third of the stock thickness, hole depth about half the dowel length, with glue grooves for squeeze-out.

Bridle joint: the tenon is the full width of the rail and is slotted into a fork; used where a rail meets a leg.

Glue-up rule: dry-fit first, apply glue to both surfaces, clamp within the open time, and leave clamps on for the full cure time before machining.

Air seasoning: stack with stickers (spacers) between courses, on a level base, under cover, ends sealed; roughly 1 year per 25 mm of thickness in humid Assam conditions.

Kiln seasoning: controlled temperature, humidity and air speed; faster than air drying but needs a schedule that avoids case-hardening and honeycomb.

Equilibrium moisture content (EMC) depends on relative humidity and temperature; wood in a covered Assam workshop settles near 12–15% MC.

Seasoning checks: split a sample and use a moisture meter; case-hardening is detected by the prong or case-hardening test.

Wood preservatives: coal-tar creosote (oil-borne, for exterior and ground contact), CCA and borax-boric acid (water-borne, boron good for interior), and PCP.

Pressure treatment (full-cell, empty-cell) forces preservative deep into the sapwood; brush application gives only shallow protection.

Preservative efficiency depends on penetration and retention: sapwood takes treatment, heartwood of many species resists it.

End grain absorbs moisture far faster than side grain, so seal or paint end grain first on exposed timber.

Decay needs moisture above about 20% MC plus oxygen and warmth; keeping wood dry is the first line of preservation.

Order of work: prepare the surface (plane, scrape, sand with the grain through grits), then fill, stain, seal, and apply the top coat.

Sanding sequence: coarse to fine, e.g. 80, 120, 180, 240 grit; remove dust between coats; never skip grits.

Wood filler matches the colour of the finished wood, not the raw wood; it fills pores and small defects before staining.

Shellac is a spirit (alcohol) finish that dries fast and seals; French polish is shellac applied with a rubber and produces a high gloss.

Oil finishes (linseed, tung) penetrate and leave a natural feel but give little protection against water and heat.

Polyurethane and nitrocellulose lacquer form a film; lacquer dries by solvent evaporation and is easily repaired by re-amalgamation.

Animal glues: hide glue (hot, reversible, strong on wood), casein (water-resistant), and fish glue; synthetic: PVA (interior, white), UF (waterproof-ish), resorcinol and epoxy (exterior).

Adhesive choice rule: PVA for interior joinery, resorcinol or epoxy for exterior and marine, contact adhesive for laminates, and hot-melt for quick temporary bonds.

Glue bond strength depends on a close-fitting joint, clean surfaces, correct clamp pressure, and adequate open and clamp time.

Scale: 1:1 full size, 1:10 for furniture, 1:50 or 1:100 for room layouts; state the scale on every drawing.

Orthographic projection: plan (top view), elevation (front/side), and section; first-angle and third-angle differ in where the views are placed.

Isometric drawing uses three axes at 120° with true lengths along them; oblique uses one face true and the other at 45°.

Line conventions: continuous thick for visible edges, dashed for hidden edges, chain-dotted for centre lines, thin for dimension and extension lines.

Dimensioning: give overall sizes plus centre-to-centre spacing; never repeat a dimension; units are millimetres by default in joinery.

Bill of materials (BOM): list each part with size (length × width × thickness), quantity, species, and wastage allowance (often 10–15%).

Timber volume in cubic feet = length (ft) × width (ft) × thickness (ft) × number of pieces; convert mm to ft by dividing by 304.8.

Cutting list rule: work from the finished size plus machining allowance; add for planing, jointing and saw kerf.

Cost estimate = material cost + labour (hours × rate) + overheads + profit margin; state assumptions explicitly.

Assam's forests supply sal (Shorea robusta), gamari (Gmelina arborea), sissoo, nahor, mango, and bamboo and cane in abundance.

Bamboo and cane craft is central to Assamese material culture: woven mats, baskets, sieves, fish traps, and furniture frames.

The Sarthebari and Hajo belt is known for bell-metal and wood work; the Majuli and Sivasagar areas for mask-making and temple wood carving.

Traditional Assamese houses use timber posts, bamboo walls and thatch or tin roofs; the ikra or reed-and-bamboo wall is a regional technique.

Wood carving appears in Vaishnavite satra doorways, columns and throne (singhasan) work, often with floral and geometric motifs.

Modern Assam wood craft combines hand tools with power tools (circular saw, router, lathe) and uses locally grown plantation timber such as gamari and rubberwood.

Cane and bamboo products of Assam are protected under geographical indication and are a major handicraft export.

Design principle in Assamese craft: motifs drawn from nature (lotus, creepers, peacock) and from the namghar architectural vocabulary.

Sustainability: prefer fast-growing plantation species and certified timber; bamboo matures in 3–4 years and is a renewable substitute for scarce hardwoods.

Workshop layout zones: timber store, marking-out bench, machining area, assembly and glue-up area, finishing area, and waste collection.

Bench height is roughly wrist height when standing; vice jaws should be just below elbow height for comfortable sawing.

Personal protective equipment: safety glasses for machining, dust mask (at least FFP2) for sanding, hearing protection near machines, and no loose sleeves or jewellery.

Machine guards: the saw blade guard, riving knife and push stick are mandatory on a circular saw; never reach over a running blade.

Dust control: local exhaust ventilation at the source, and awareness that fine wood dust is a respiratory sensitiser and a fire risk.

Electrical safety: RCD/ELCB protection, no trailing leads, isolate and lock off before changing blades or bits.

First aid: treat cuts by pressure and clean dressing; for eye injury do not rub, flush with clean water and seek help; know the location of the first-aid box and fire extinguisher.

Project workflow: design → working drawing → cutting list → material selection → machining → jointing → assembly → finishing → inspection.

Quality check points: squareness (diagonals equal), flatness (straightedge), joint tightness (no visible gap), and finish (no sanding scratches across the grain).