Files

T

davide 0908191ef3 add tolleranze-iso skill: ISO 286-1 tolerance and fit selection consultant

Complete ISO 286-1 skill for mechanical designers covering:
- Fit selection (clearance/transition/interference) with intake protocol
- IT grades 1–16 with required machining processes for bores and shafts
- Full functional elements reference: rolling bearings, gears, keys (DIN 6885),
  Seeger rings, cylindrical pins, plain bushings, lip seals, splined profiles,
  couplings, linear guides (14 sections total)
- Fundamental deviations table (bores A–ZC, shafts a–zc, Ø1–500 mm)
- Surface roughness Ra correlation by IT grade
- Python calculator (scripts/calculate_fit.py) with JSON data files for exact
  clearance/interference computation and formatted fit data sheet output
- Visual input support: analyses attached drawings, sketches, photos
- Description ≤ 1024 chars, written in English for optimal trigger accuracy

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

2026-03-23 12:20:53 +01:00

3.4 KiB

Raw Permalink Blame History

Fit Selection Matrix — Function to Coupling

Clearance Fits

Loose clearance — free movement

Fit	Typical application	Indicative clearance (Ø50)
H11/c11	Articulated joints, cranks, very loose couplings	0.12 – 0.45 mm
H9/d9	Connecting rods, flanges with generous clearance	0.06 – 0.20 mm
H8/e8	Long shafts, joints with misalignment	0.04 – 0.11 mm

Functional clearance — sliding with lubrication

Fit	Typical application	Indicative clearance (Ø50)
H8/f7	Sliding bushings, guides, pins	0.025 – 0.09 mm
H7/f7	Standard sliding fits	0.020 – 0.07 mm
H7/g6	Precision fits, rotating pins	0.010 – 0.05 mm
H6/g5	Spindles, high-precision shafts	0.004 – 0.025 mm

Small clearance — centering

Fit	Typical application	Indicative clearance (Ø50)
H7/h6	Positioning, removable centering	0 – 0.025 mm
H6/h5	High-precision positioning	0 – 0.013 mm

Transition Fits

May result in slight clearance or slight interference — the statistical distribution of manufacturing determines the actual type on each individual part.

Fit	Typical application	Clearance/Interference (Ø50)
H7/js6	Removable pins, loose pulleys	±0.008 mm
H7/k6	Bushings, rings, removable keys	−0.002 … +0.018 mm
H7/m6	Sleeves, hot-removable gears	−0.009 … +0.011 mm
H6/k5	High precision, precision gears	−0.002 … +0.009 mm

Practical rule: k6 is press-fit and removed with a puller. m6 requires a heavier press or heating. Both are "removable" but require tooling.

Interference Fits

⚠️ Before specifying an interference, always calculate:

Contact pressure at the joint
Hoop stress in the hub
Radial stress in the shaft (if hollow)
Transmissible torque by friction (verify sufficiency)
Assembly temperature if thermal

→ Use fundamental-deviations.md for exact values, then apply Lamé equations.

Fit	Typical application	Indicative interference (Ø50)	Assembly
H7/n6	Fixed bushings, sealing rings, bronze bearings	0 … 0.033 mm	Press (up to 10 kN on Ø50)
H7/p6	Gears on shaft, fixed pulleys, hubs	0.009 … 0.042 mm	Press or thermal
H7/r6	Medium-torque transmission hubs	0.020 … 0.055 mm	Thermal (Δt = 80–150°C)
H7/s6	High-torque transmission	0.031 … 0.066 mm	Thermal (Δt = 150–250°C)
H7/u6	Bronze/cast-iron bushings, maximum interference	0.053 … 0.094 mm	Thermal (Δt ≥ 250°C)
H6/p5	Inner rings of P5/P4 precision bearings	—	Thermal

Interference verification formulas

Contact pressure:    p = δ / [d × (C_o/E_o + C_i/E_i)]
  where δ = actual interference (mm)
        d = nominal diameter (mm)
        C_o, C_i = shape coefficients (from Lamé)
        E_o, E_i = elastic moduli of materials

Transmissible torque: Mt = p × π × d² × L × μ / 2
  where L = contact length
        μ = friction coefficient (0.08–0.12 thermal, 0.12–0.15 press)

Assembly temperature: ΔT = δ_max / (α × d)  [°C]
  where α = thermal expansion coefficient (steel: 11.5×10⁻⁶ /°C)
  + add 30–50°C for assembly clearance

For bearings, gears, valves, keys, Seeger rings, pins, bushings, seals, and all other functional elements → see functional-elements.md (includes decision flowchart).

3.4 KiB Raw Permalink Blame History Unescape Escape