Meisterprüfung Metalltechnik cheat sheet

Tensile test per DIN EN ISO 6892-1: Rp0.2 is the 0.2 % offset yield strength, Rm the tensile strength, A the elongation after fracture; the engineering stress-strain curve is not the true curve.

Carbon equivalent CEV = C + Mn/6 + (Cr+Mo+V)/5 + (Cu+Ni)/15; steels with CEV above about 0.45 tend to cold cracking and need preheating.

Iron-carbon diagram: eutectoid at 0.8 % C and 723 °C (pearlite); eutectic at 4.3 % C and 1147 °C (ledeburite). Ferrite is soft, cementite hard and brittle.

Hardenability is tested by the Jominy end-quench test; hardness penetration depends on alloy content and austenitising temperature, not on the cooling rate alone.

Machinability groups per DIN EN 10027 / ISO: P steels, M stainless, K cast iron, N non-ferrous, S superalloys, H hard materials; cutting speed decreases from N to S to H.

Welding: heat input Q = k · U · I / v (kJ/mm, k ≈ 0.8–0.9 for MAG); t8/5 cooling time governs hardness and toughness in the heat-affected zone.

Fits per ISO 286: hole basis H gives clearance for shafts a–h, transition for j–n, interference for p–zc; IT grades 5–7 for precision fits, 8–11 for coarse work.

Surface roughness: Ra is the arithmetic mean roughness, Rz the mean peak-to-valley height of five single measurements; Ra ≈ Rz/4 to Rz/6 as a rough rule.

Cutting speed vc = π · d · n / 1000 (m/min with d in mm); rearranged n = 1000 · vc / (π · d). Feed per tooth fz = vf / (z · n).

Right triangle: c² = a² + b², sin α = a/c, cos α = b/c, tan α = a/b; sine rule a/sin α = b/sin β = 2R.

Torque M = F · r; power P = 2π · n · M (n in s⁻¹) = F · v; efficiency η = P_out / P_in.

Thermal expansion Δl = l0 · α · ΔT; steel α ≈ 11–13 · 10⁻⁶ K⁻¹, aluminium ≈ 23 · 10⁻⁶ K⁻¹, grey cast iron ≈ 10–11 · 10⁻⁶ K⁻¹.

Stress σ = F/A, strain ε = Δl/l0, Hooke's law σ = E · ε in the elastic range; E steel ≈ 210 GPa, aluminium ≈ 70 GPa.

Technical drawing per ISO 128/ISO 7200: first-angle projection (European) places the view from the left on the right; third-angle projection is mirror-inverted.

ISO tolerance designation example 40 H7: nominal 40 mm, hole, IT7; limits = nominal + deviations in µm, e.g. H7 for 30–50 mm gives +25/0 µm.

CAD: parametric models are driven by constraints and dimensions; a fully constrained sketch shows no degrees of freedom, and drawing derivation keeps associativity with the 3D model.

Costing: manufacturing cost = direct material + direct labour + manufacturing overhead; cost of goods sold = manufacturing cost + admin + sales overhead; add profit margin for the offer price.

Machine-hour rate = (depreciation + space + energy + maintenance + imputed interest and wages) / planned machine hours per year.

Break-even quantity x = fixed costs / (price per unit − variable cost per unit); contribution margin per unit = p − kv.

Depreciation: linear = (acquisition cost − residual value) / useful life; declining balance applies a constant percentage to the book value; imputed depreciation uses replacement value.

Key figures: liquidity ratio = liquid funds / short-term liabilities; return on sales = profit / revenue; equity ratio = equity / total assets.

Offer calculation per VOB/B or BGB: unit prices include overheads and profit; quantities in the bill of quantities are at the client's risk, prices at the contractor's risk.

Payment terms: discount D = (discount rate / (100 − discount rate)) · (360 / (payment period − discount period)) gives the annualised cost of skipping the discount.

Contract formation under BGB: two matching declarations of intent (offer and acceptance); a contract for work and services (Werkvertrag) requires success, a service contract (Dienstvertrag) only effort.

Warranty for work contracts: 2 years for buildings and works, 5 years for buildings; defects must be notified within the limitation period, and the client may choose remedy, reduction, cancellation or damages.

Product liability per ProdHaftG: strict liability for defective products, 10-year maximum liability period, no liability for development risks; fault-based liability under § 823 BGB is separate.

Handwerk: the Handwerksordnung requires entry in the Handwerksrolle for a craft trade; Annex A trades need a master craftsperson or an equivalent qualification, Annex B trades do not.

Working time Act (ArbZG): 8 hours per working day, extendable to 10 hours if averaged over 6 months; minimum 11 hours rest after the shift; breaks of 30 min after 6 h and 45 min after 9 h.

Dismissal: ordinary dismissal requires the notice period of § 622 BGB (4 weeks to the 15th or end of month, rising with tenure) and, in establishments over 10 employees, protection against unfair dismissal under KSchG.

Social insurance: employer and employee each pay half of health, pension, unemployment and care insurance; accident insurance is paid by the employer alone.

Four-step method: prepare (explain the goal and motivate), demonstrate and explain (the trainer performs, the trainee observes), imitate and practise (the trainee performs while the trainer corrects), consolidate (independent practice and transfer).

Learning objectives are formulated with observable behaviour, conditions and standard, e.g. 'the trainee drills a through-hole to ±0.1 mm within 10 minutes using the pillar drill'.

Training plan per Ausbildungsrahmenplan and betrieblicher Ausbildungsplan; the trainee must keep a written or electronic training record (Ausbildungsnachweis).

Legal frame: BBiG regulates the training contract, probation (1–4 months), the final examination and the trainer's personal and professional suitability.

Learning domains: psychomotor (skills), cognitive (knowledge), affective (attitudes); Bloom's taxonomy orders cognitive levels from remember to create.

Feedback rules: describe behaviour, not the person; give feedback promptly, concretely and in a two-way dialogue; separate observation from interpretation.

Motivation: intrinsic motivation arises from autonomy, competence and relatedness; extrinsic incentives such as bonuses act short-term and can displace intrinsic drive.

Legal hierarchy: EU framework directive and national law (ArbSchG, BetrSichV) are binding; DGUV regulations and rules concretise them; the TOP principle orders measures as technical, organisational, personal.

Risk assessment per § 5 ArbSchG: identify hazards, assess risk, define measures, implement, check effectiveness, document and review regularly.

Hazardous substances: observe the workplace limit value (AGW) as an 8-hour shift average; substitute first (STOP: substitution, technical, organisational, personal protection), and use PPE only as the last barrier.

Noise: action level 80 dB(A), upper action level 85 dB(A) requiring hearing protection; an exposure above 85 dB(A) requires a hearing protection programme and audiometry.

Machine safety per Machinery Directive / BetrSichV: guards must be fixed where possible, interlocked where access is frequent; safety distances per DIN EN ISO 13857.

Electrical work: five safety rules - disconnect, secure against reconnection, verify absence of voltage, earth and short-circuit, cover adjacent live parts.

Fire classes A (solids), B (liquids), C (gases), D (metals), F (fats); metal fires such as magnesium require dry powder class D, never water or CO2.

Waste hierarchy per KrWG: avoidance before reuse before recycling before recovery before disposal; waste code assignment per AVV (European Waste Catalogue).

Metalworking fluids: water-mixed coolants must be monitored for concentration, pH (typically 8.5–9.5), nitrite and microbial load; disposal requires separation of oil and water.

Energy efficiency: compressed air is the most expensive energy carrier - leakage of a 3 mm hole at 6 bar costs several thousand kWh per year; leak detection and pressure reduction are primary measures.

Energy per part = (machine power · machining time) / parts per cycle; dry machining or minimum quantity lubrication reduces both energy and coolant disposal cost.

Emissions: VOC from solvents, dust from grinding and welding fumes require capture at source; welding fume is classified as carcinogenic (Group 1) and demands extraction.

Sustainability: CO2 footprint = activity data × emission factor; recycled steel requires far less energy than primary steel, and scrap sorting raises recycling value.

Legal duties: Federal Immission Control Act (BImSchG), Water Resources Act (WHG) with the requirement to handle substances hazardous to water carefully, and the Energy Services Act for large companies.

Project structure: milestone plan and work breakdown structure; each work package has a defined result, duration, resources and responsible person.

Time planning: critical path is the longest chain of dependent activities; total float = latest finish − earliest finish; a delay on the critical path delays the project end.

Cost planning: budget = sum of work package costs plus a risk reserve; earned value: CPI = EV/AC, SPI = EV/PV; CPI below 1 means cost overrun.

Risk management: identify, assess probability and impact, define measures, assign owner, monitor; a risk matrix ranks risks by probability × impact.

Documentation: drawings with revision index, parts lists, test records, calculation evidence, operating instructions and a complete bill of materials form the acceptance file.

Presentation: structure as introduction, problem, solution, evidence, benefit, outlook; a rule of thumb is about one slide per minute of talk, with a clear core message per slide.

Acceptance: define acceptance criteria before execution, test them measurably, and record deviations with their correction in an acceptance protocol.