ISO Fit & Tolerance Selector

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

Nominal Diameter (d)

ISO Step: over 18 up to 30 mm

Desired 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

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

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

–

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.