ISO Fit & Tolerance Selector

H7 Hole-Basis System. Interactive matrix, reverse lookup, and unit conversion.

Demo rapida (1-Click):

Nominal Diameter (d)

ISO Step: over 18 up to 30 mm

Desired Fit

Hole (H7)

+21 / 0 µm

25.000 / 25.021 mm

Shaft (g6)

-7 / -20 µm

24.993 / 24.980 mm

Fit Condition

Clearance: 7 - 41 µm

Clearance fit

Relative Tolerance Zone Positions

Hole (H7) Shaft Zero Line

Instant ISO Fits Comparison Table Click any row to select fit

Fit	Shaft Dev.	Fit Condition	Min / Max	Action

Machining & Surface Finish Guidelines

Recommended Shaft Machining:

Precision Turning / Grinding

Surface roughness: Ra 0.8 µm

Recommended Hole Machining:

Precision Reaming

Surface roughness: Ra 1.6 µm

Pulley definition: Direct Teeth (z₁, z₂) Target Ratio τ (z₂ / z₁)

Belt Pitch / Profile

Driver Pulley (z₁)

dp₁: 38.20 mm

Driven Pulley (z₂)

dp₂: 76.39 mm

Desired Center (C₀)

Ratio: 1 : 2.00

Exact Center Dist. (C)

201.42 mm

Δ: +1.42 mm vs target

Rounded Belt Teeth (zb)

116 teeth

Lp: 580.00 mm (rounded)

Wrap Angle (θ₁)

169.1°

Ratio: 2.000

Teeth in Mesh (z_mesh)

11.3 teeth

Optimal (> 6 teeth)

Load Input Mode:

Power P [kW] & Speed n₁ Direct Torque M₁ [Nm]

Gear Definition:

Target Ratio τ Teeth z₁, z₂ Center Dist. i

Active Modifiers: Auto-Teeth (Tol. % on τ) Lock Module (m) Lock Face Width (L)

Tooth Profile

ISO 54 / Standard

Motor Power (W)

ω₁: 151.8 rad/s

Driver Speed (n₁)

rpm

Motor shaft

Target Ratio (τ = z₁/z₂ < 1)

z₂: 40 (τ_eff: 0.500)

Pinion Teeth (z₁)

z₁ ≥ 17 (spur gears)

Profile Shift (xr₁)

Typical range: 0.0 ÷ 0.5

Elastic Constant (Kε)

GPa

Steel - Steel = 35 GPa

Hertz Limit (σH lim)

MPa

Quenched & Tempered: ~550 MPa

Optimal Teeth Combinations (Starting from z_min)

Click any combination to apply geometry and update the transmission scheme

Ranking [Hertz ϕ & Error]

z₁	z₂	τ_eff	Error on τ (%)	Hertz ϕ & Face L	Lewis σL	Action

Standard Module (m)

m = 2.00 mm

Series 1: Recommended

Face Width Factor (ϕ)

ϕ = 0.82

Optimal (L = 32.8 mm)

Lewis Bending Check

412 MPa

✓ Verified (σL ≤ 800 MPa)

Exact Center Dist. (i)

60.00 mm

dp₁: 40.0 | dp₂: 80.0 mm

Analytical Steps & Design Parameters z₁ ≥ z_min → Pass

1. Min Module (Hertz ϕ=1): 1.78 mm

2. Chosen UNI Module: 2.00 mm

3. Limit ϕ (at σH lim): 0.710

4. Face Width L: 28.4 mm

5. Tangential Force Fc: 1810 N

6. Lewis Factor (y): 0.329

7. Lewis Stress (σL): 387 MPa

8. Material Model: Kε = 35 GPa

Tooth Profile

Nominal Module (m)

mn for helical gears

Face Width (L)

Gear thickness

Driver Speed (n₁)

rpm

Pinion Teeth (z₁)

Driven Teeth (z₂)

Profile Shift (xr₁)

Elastic Constant (Kε)

GPa

Hertz Limit (σH lim)

MPa

Lewis Limit (σL lim)

MPa

Max Rated Power (W_max)

40.60 kW

Limited by Pitting (Hertz)

Max Driver Torque (M₁)

596.5 Nm

Pinion shaft

Wear Capacity (Hertz)

40.60 kW

Pitting limit

Tooth Strength (Lewis)

163.45 kW

Bending limit

Mechanical Parameters Summary Verification Complete

Pinion Pitch (dp₁): 115.0 mm

Wheel Pitch (dp₂): 195.0 mm

Exact Center Dist. (i): 155.00 mm

Max Tangential Force (Fc): 10374 N

Lewis Factor (y): 0.348

Face Width Ratio (ϕ): 0.522

Pitch Line Gear Meshing Scheme Pitch circles & pitch point contact C

Torque transmitted by the shaft

Torque from

Power P

Speed n

rpm

Bearings (supports) and data

Naming

Shaft length L (A → B)

Bearing A at x

Bearing B at x

Axial load on

Pressure angle θ

Bearing life L

10⁶ rev

Bearing type

Rotation seen from B

Used by the gears set "from the mating gear"

Catalog C, bearing 1

0 = not chosen yet

Catalog C, bearing 2

0 = not chosen yet

Elements on the shaft (x from the left end)

Gear forces

Element 1

Position x

Pitch diameter

Helix angle

Torque

Share of Mt

Force directions

Ft direction

Fr direction

Fa direction

Force V

Force H

Axial force

Fa offset (H)

Element 2

Position x

Pitch diameter

Helix angle

Torque

Share of Mt

Force directions

Ft direction

Fr direction

Fa direction

Force V

Force H

Axial force

Fa offset (H)

Element 3

Position x

Pitch diameter

Helix angle

Torque

Share of Mt

Force directions

Ft direction

Fr direction

Fa direction

Force V

Force H

Axial force

Fa offset (H)

Element 4

Position x

Pitch diameter

Helix angle

Torque

Share of Mt

Force directions

Ft direction

Fr direction

Fa direction

Force V

Force H

Axial force

Fa offset (H)

Reaction A

Reaction B

Required bearing C (A / B)

Most stressed section

Loads, bending moments and torque

Section to design

Section at x

Real sections: which one is really critical? (optional)

Hint

D (shoulder)

Keyway

Section 1

Section 2

Section 3

Section 4

Loads on the critical section

Bending moment Mf

N·m

Bending cycle

Torsion cycle

Axial force N (tension +)

The section transmits the shaft torque Mt

Material and life

Steel (table)

Quenched and tempered steels, EN 10083 (+QT): σR = minimum Rm, σs = minimum Re, σLF ≈ 0.5·σR (estimate: use the course value if you have it).

Ultimate strength σR

MPa

Yield strength σs

MPa

Fatigue limit σLF

MPa

Rotating bending, 10⁶ cycles

Required life

Geometry, notch and finish

Critical detail

Shoulder ratio D/d

–

First attempt: 1.1–1.3

Fillet radius r

Bearing chamfer: see catalog

Surface finish (b₂)

Required safety factor X

–

Minimum diameter

Chosen diameter (bearing bore)

Fatigue safety factor

Yield safety factor

Coefficients and stresses at the chosen diameter

Kt bending / torsion --

q bending / torsion --

Ke / Ke' --

b₁ (size) / b₂ (finish) --

Fatigue strength σN --

σ bending / τ torsion (nominal) --

σa,eq (alternating, Von Mises) --

σm,eq (mean, max principal) --

Goodman diagram

Dimensions for CAD

Preliminary sizing of one section.