Two gears in mesh
1500pinion rpm
→
500gear rpm
→
×3.00torque
Interactive Gear Guide
How a gear pair works
Change the numbers, watch the gears respond. Every value below updates live — the same maths our engineers use on the shop floor.
Playground
Design a gear pair
Adjust the module, teeth, pressure angle and helix angle of two meshing gears (a small pinion driving a larger gear) and see the geometry, ratio and motion change in real time.
Pinion tooth Z₁
Gear tooth Z₂
Gear ratio i3.00 : 1Z₂ / Z₁
Pitch dia. d₁ / d₂108 / 324 mmm · Z
Outside dia. OD120 / 336 mmm (Z + 2)
Root dia. RD93 / 309 mmm (Z − 2.5)
Center distance a216 mm(d₁ + d₂) / 2
Diametral pitch DP4.23 /in25.4 / m
Circular pitch p18.85 mmπ · m
Add. / Ded.6.0 / 7.5 mm1m / 1.25m
Contact ratio ε1.65teeth in mesh
Estimates for an external, standard involute gear pair, normal module m. Real designs add profile shift, tip relief and tolerances — talk to our engineers for a manufacturing spec.
Reference
20 gear parameters, explained
The vocabulary of gear design — what each parameter means and why it matters in heavy industry.
Number of teeth Z
The total teeth on the gear. Drives gear ratio, speed reduction, torque multiplication and tooth strength.
Module m metric
The single most important parameter — it sets tooth size.
m = d / Z
Common in heavy industry: m 4, 5, 6, 8, 10, 12, 16, 20, 25, 30.
Diametral pitch DP imperial
The American equivalent of module. Higher DP means smaller teeth.
DP = Z / d
Pressure angle α
The angle of the tooth profile. A higher angle gives a stronger tooth but a little more noise.
- 20° — most common worldwide
- 14.5° — older systems
- 25° — high-load applications
Pitch diameter d
The theoretical diameter where two gears mesh — the gear's working diameter.
d = m · Z
Outside diameter OD
The actual physical outer diameter of the gear.
OD = m (Z + 2)
Root diameter RD
Diameter at the bottom of the teeth. Critical for strength, interference and cutting depth.
RD = m (Z − 2.5)
Face width b
The width of the tooth across the gear face. Wider = higher load capacity. Heavy gears often run 50–300 mm.
Helix angle β
For helical gears. 15–30° in industrial gearboxes. A higher angle runs smoother and quieter but adds axial thrust.
Gear material
Choice drives heat treatment, hardness and wear resistance.
- 42CrMo4, C45
- 20MnCr5 (case hardened)
- Cast iron
- Bronze (worm gears)
Heat treatment
Sets tooth hardness, e.g. 50–60 HRC.
- Induction hardening
- Carburizing
- Nitriding
- Normalizing
Backlash
A small clearance between mating teeth — needed for lubrication, thermal expansion and smooth running.
Tooth profile
The shape of the tooth flank.
- Involute (standard)
- Cycloidal (rare)
- Stub tooth (special)
Quality / accuracy grade
How precise the gear is cut. Heavy industry typically uses DIN grade 8–10.
- DIN 3962 / 3967
- AGMA
- ISO 1328
Center distance a
The distance between two meshing gear centers — critical for assembly and alignment.
a = (d₁ + d₂) / 2
Gear ratio i
Determines the speed and torque output of the pair.
i = Z₂ / Z₁
Addendum & dedendum
Tooth height above and below the pitch circle.
Addendum = 1 × m · Dedendum = 1.25 × m
Contact ratio
How many teeth are in contact at once. Higher means smoother, quieter running.
Lubrication
Critical for heavy-load gears in cement, mining and quarries.
- Grease
- Oil bath
- Forced lubrication
Mounting & hub
How the gear fixes to its shaft.
- Bore diameter & keyway
- Set screws
- Hub length
- Taper bush or shrink fit
Need a gear built to spec?
From a worn sample or a full drawing — we manufacture and refurbish gears for cement, mining, sugar and steel plants across Egypt.