UPMSP Class 12 Wood Craft cheat sheet

Softwoods come from gymnosperms (conifers) and have no vessels; hardwoods come from angiosperms and contain vessels (pores) visible as dots on end grain.

Cross-section terms: pith at the centre, heartwood (dead, darker, more durable) inside, sapwood (living, pale, sap-conducting) outside, then cambium, inner bark (phloem) and outer bark.

Annual ring = one year of growth: earlywood (spring wood) is light and wide-walled-thin; latewood (summer wood) is dark and dense, so latewood percentage predicts strength and density.

Moisture content formula: MC% = (wet mass − oven-dry mass) / oven-dry mass × 100.

Density is measured at a stated moisture content (commonly 12%); basic density uses oven-dry mass over green volume.

Grain and figure descriptors: straight, interlocked, spiral, wavy; figure types include stripe, roe, fiddleback, quilt and burl.

Shrinkage is anisotropic: tangential > radial > longitudinal (longitudinal is negligible), which is why flatsawn boards cup and quartersawn boards stay flatter.

Identification cues: colour, odour (e.g. camphor, sandalwood), hardness, pore arrangement (ring-porous vs diffuse-porous), ray width and resin canals in softwoods.

Air seasoning reaches equilibrium with local climate, typically 12–18% MC in Indian conditions; kiln seasoning can reach 6–10% MC and is faster but capital-intensive.

Kiln schedules control dry-bulb temperature, wet-bulb temperature (hence relative humidity) and air velocity; the wet-bulb depression drives the drying rate.

Drying defects: surface checking, end splitting, case-hardening, honeycombing and collapse - all caused by drying too fast or by shrinkage stress gradients.

Equilibrium moisture content (EMC) falls as relative humidity falls; wood in service should be dried to the EMC of its final environment to limit movement.

Preservation methods: pressure impregnation (full-cell, empty-cell), hot-and-cold open-tank, brushing, spraying, dipping and diffusion.

Common preservatives: coal-tar creosote (railway sleepers, poles), CCA and other water-borne salts (interior/ground contact), boron compounds (interior, non-fixating), and oil-borne pentachlorophenol.

Preservative uptake is expressed in kg/m³ of treated wood; penetration depth and retention are both specified, not just surface coverage.

Seasoning before preservation is essential: green timber resists penetration and traps moisture under the treated shell.

Marking tools: try square (90°), bevel/mitre square (any angle), marking gauge (line parallel to an edge), mortise gauge (two pins), dividers and marking knife.

Saws by tooth form: rip saw (chisel teeth, filed across, cuts along grain), crosscut saw (knife-pointed teeth, cuts across grain), tenon saw (fine, back-supported), dovetail saw and coping saw.

Plane family: jack plane (general stock removal), smoothing plane (finishing), rebate plane, plough plane (grooves), router plane (cleaning groove bottoms), block plane (end grain).

Chisels are sized by blade width in mm; firmer chisels are for heavy paring, bevel-edge for joints, mortise chisels are thick for levering out waste.

Boring tools: brace and bit, hand drill, auger bit (deep holes), Forstner bit (flat-bottomed holes), gimlet (starting screws).

Claw hammer weight is marked in grams or pounds; the claw is for extraction, the face for driving - never strike a chisel with a hammer.

Measuring and testing: steel rule, tape, calipers, straightedge, winding sticks (twist detection) and feeler gauge for checking flatness.

A tool's cutting edge is a wedge; rake angle, clearance angle and bevel angle together define cutting efficiency and edge life.

Sharpening sequence: grind (hollow or flat bevel) → hone on oilstone/waterstone → strop on leather; remove the burr (wire edge) by honing the flat face.

Typical bevel angles: chisel 25° (with a 30° micro-bevel), plane iron 25–30°, mortise chisel 30–35°, scraper burr turned at about 45°.

Grit progression for waterstones: coarse (~220–400) to shape, medium (~1000) to hone, fine (~4000–8000) to polish.

Flatness of the back is established once and maintained; a chisel is not sharp until the back and bevel meet at a polished edge.

Set (bent) saw teeth are corrected with a saw set and a saw vice; jointing (filing the tooth line flat) precedes re-filing and re-setting.

Saw tooth geometry: crosscut teeth filed at about 60–75° bevel with fleam; rip teeth filed square across at about 90°.

Plane maintenance: flatten the sole on abrasive paper on a flat reference, check the cap iron fit, and keep the mouth throat clear.

Storage rules: oiled or waxed metal surfaces, chisels in rolls, saws hung or in cases, and files never stored rubbing against each other.

Circular saw: blade diameter, kerf, tooth count (few teeth = ripping, many = crosscutting) and rpm rating must match the machine; guard and riving knife are mandatory.

Band saw: blade width sets the minimum radius of cut; teeth per inch, blade tension, guide adjustment and thrust bearing clearance determine cut quality.

Planer (surface planer) trues one face and one edge; thicknesser (thickness planer) brings to parallel thickness - sequence is face, edge, then thickness.

Router: collet size (6 mm, 8 mm, 12 mm or 1/4 in, 1/2 in), feed direction against cutter rotation, and depth of cut limited to roughly the bit diameter per pass.

Mortiser (hollow chisel) and tenoner produce square mortises and matching tenons; drill press speed falls as bit diameter rises.

Sanding machines: disc sander (flat faces, edge work), belt sander (surfaces), spindle sander (curves), drum sander (thickness calibration).

Lathe: spindle turning uses a spur centre and tailstock live centre; faceplate turning uses screws; tool rest is set close to the work and the speed is low for large diameters.

Machine safety rule: never reach across a running cutter, use push sticks within 300 mm of the blade, and isolate power before changing blades or bits.

Width joints: butt (glued or nailed), dowelled, biscuit, tongue-and-groove, rebate, and loose-tongue spline.

Corner joints: mitre, half-lap, bridle, dovetail (through, half-blind, secret mitre), box/finger joint and comb joint.

Frame joints: mortise and tenon (haunched, stub, through), bridle, dowel and loose-tenon; tenon thickness is about one-third of the rail thickness.

Housing and carcase joints: dado/housing, stopped housing, rebate, and sliding dovetail for shelves that must not pull out.

Dovetail proportioning: tails about one-third the board thickness at the narrow end, pins spaced evenly, angle about 1:6 in softwood and 1:8 in hardwood.

Fasteners: wood screws (countersunk, round, raised head), nails (wire, cut, clout), coach screws, bolts, and modern confirmat/dowel systems.

Adhesives: PVA for interior, cross-linking PVA (D3/D4) and polyurethane for damp conditions, epoxy for gap filling, animal glue for veneering and reversibility.

Glue joint strength requires clean, freshly prepared surfaces, close fit, adequate clamp pressure, and full cure time before machining.

Orthographic projection: plan, front elevation and side elevation drawn to a stated scale; first-angle and third-angle layouts must be labelled.

Isometric drawing gives a 3D view on 30° axes; oblique uses one face true shape; perspective uses vanishing points for realism.

Standard furniture dimensions (mm, typical): dining table height 750, seat height 450, desk height 750, kitchen counter 850–900, wardrobe depth 600.

Ergonomic rules: seat depth about 400–450 mm, backrest angle 100–110°, clear knee space at least 600 mm wide and 650 mm high under a table.

Design brief elements: function, user, space envelope, material choice, joint/construction logic, finish and cost target.

Estimation method: prepare a bill of quantities (parts list with length × width × thickness × quantity), add wastage allowance (typically 10–15% for solid timber), then price by volume.

Board-foot and cubic-metre conversions: 1 m³ = 35.315 ft³; 1 ft³ = 1728 in³; a board foot = 144 in³ (1 in thick × 12 in × 12 in).

Cost sheet = material + hardware + adhesive/finish + labour (time × rate) + overheads + margin; show each line separately.

Sanding sequence: start at 80–120 grit, progress 150 → 180 → 240; never skip more than one grit step, and raise the grain between coats where needed.

Scrape or plane before sanding: a sharp cabinet scraper removes tear-out and burnishing that sandpaper cannot fix.

Filling: open-grained woods need paste wood filler before finishing; defects are filled with matching putty after sealing.

Stains: water stain (raises grain, needs pre-dampening), oil stain (slow, even), spirit stain (fast drying, poor light-fastness), and chemical/fumed staining.

Film finishes: shellac (French polish, spirit-based), nitrocellulose lacquer, polyurethane, melamine, and water-borne acrylics; each has different build and drying behaviour.

French polish procedure: rubber (fad) charged with shellac and a drop of oil, applied in overlapping circles then straight strokes, bodying → spiriting → stiffing.

Oiled and waxed finishes: penetrating oil (linseed/tung) plus wax gives a low-build, repairable finish; polyurethane gives higher wear resistance.

Finishing environment: dust-free, 20–30 °C, adequate ventilation, and finish coats thinned per manufacturer's ratio; runs are removed by cutting back with fine abrasive.

PPE baseline: safety glasses, hearing protection above 85 dB(A), dust mask/respirator, and no loose clothing, jewellery or open footwear near machines.

Machine guarding: fixed guards, interlocked guards, riving knife and anti-kickback fingers on circular saws; push sticks and featherboards keep hands clear.

Kickback prevention: support the workpiece fully, keep the blade sharp and correctly set, and never rip a short board without a push block.

Wood dust is a carcinogen (nasal cancer risk); extract at source with a dust collector and never use compressed air to clear dust in the breathing zone.

Electrical safety: earth/ground all machines, use residual-current device (RCD/ELCB) protection, and isolate and lock out before maintenance.

Fire: store solvents in closed metal cabinets, keep oily rags in a self-closing bin (spontaneous combustion risk), and keep extinguishers (CO₂/foam) accessible.

Environmental care: choose certified/renewable timber, use low-VOC finishes, segregate and recycle offcuts and sawdust, and dispose of solvent waste as hazardous waste.

First aid: cuts - clean and pressure-dress; eye foreign body - do not rub, flush and seek medical help; report every near-miss.

Work sequence: read drawing → select and check material → set out and mark (face side and face edge marks) → cut → joint → dry assemble → glue and clamp → clean up → finish.

Face-side and face-edge marks establish the reference datum; all marking and machining is taken from these two surfaces.

Cutting order rule: cut to length after squaring one end; never cut all parts before checking the first joint for fit.

Clamping: distribute clamps evenly, use cauls to spread pressure, check diagonals for square before the glue sets, and wipe squeeze-out immediately.

Trial assembly without glue exposes tight joints, twist and misalignment before the irreversible step.

Project costing and time plan: list operations with estimated minutes, sequence them so glue-ups happen last in a session, and record actual versus planned time.

Quality check points: squareness (diagonals equal), flatness (winding sticks), joint tightness (no visible gap), and surface free of tear-out and glue stains.

Final inspection against the drawing: dimensions within tolerance (commonly ±1 mm for furniture parts), hardware aligned, finish uniform and edges eased.