Glossary

A

3 terms

Addendum: The radial distance from the pitch circle to the tip of a gear tooth. Usually equal to one module on a standard gear.
AGMA: American Gear Manufacturers Association. Publisher of US gear-quality standards (e.g. AGMA 2000-A88 and the newer AGMA 2015) and load-rating standards.
Anodizing: Surface treatment that grows an oxide layer on aluminum parts for corrosion resistance, hardness, or color. Common on aluminum timing belt pulleys.

B

3 terms

Backlash: The clearance between mating gear teeth, measured along the pitch circle. Too much causes positioning error; too little causes binding and overheating.
Bevel gear: A gear with conical pitch surfaces, used to transmit motion between intersecting (usually 90°) shafts. Spiral-bevel and straight-bevel are the two main variants.
Black-oxide: A controlled-rust surface treatment producing a thin dark layer for mild corrosion resistance and aesthetic finish. Common on steel transmission parts.

C

6 terms

Carburizing: A heat-treatment process that diffuses carbon into the surface layer of low-carbon steel, then hardens it. Produces a hard wear-resistant case over a tough core.
Case depth: The depth from the surface to which a part has been hardened by a case-hardening process. Specified in millimeters and measured on a hardness traverse.
Center distance: The distance between the rotational axes of two meshing gears. Drives the kinematic design of any gear pair.
CMM: Coordinate Measuring Machine. Uses a touch-probe to measure dimensional features on a part. Wolfer's envelope: Ø 0–800 mm.
Contact ratio: The average number of tooth pairs in contact during one mesh cycle. Higher values produce smoother motion and lower noise.
Couplings: A device that connects two rotating shafts to transmit torque. May be rigid, flexible (jaw, diaphragm, bellows), or torque-limiting.

D

3 terms

Dedendum: The radial distance from the pitch circle to the root of a gear tooth. Slightly larger than the addendum to provide tooth-tip clearance.
Diametral pitch (DP): The number of gear teeth per inch of pitch diameter. Used in imperial gear specifications; the inverse concept of module.
DIN: Deutsches Institut für Normung — the German national standards body. DIN 3962/3963 is the German gear-tolerance standard widely used by European OEMs.

E

1 term

EN 10204 3.1: European standard for material inspection certificates. A "3.1" certificate is issued by the manufacturer's authorized inspection authority. Wolfer ships 3.1 certificates by default.

F

3 terms

Face width: The axial length of the gear tooth, measured along the pitch cylinder.
FEA: Finite-element analysis. Numerical simulation method used to validate bending stress and contact stress on heavily loaded gears before first cut.
Flank: The working surface of a gear tooth between the tip and the root, where contact with the mating tooth occurs.

G

2 terms

Gear ratio: The ratio between the number of teeth on the driven and the driving gear. Determines the speed and torque relationship across the pair.
Grinding: A finishing operation that removes small amounts of material to achieve final dimensional accuracy and surface finish. Wolfer uses YK7236 / YK7250 grinders for ISO 1328 Class 5 accuracy.

H

4 terms

Hardness: Resistance to localized plastic deformation. Specified on the Rockwell (HRC), Vickers (HV) or Brinell (HB) scales depending on the material and depth.
Heat treatment: Controlled heating and cooling cycle that changes the metallurgical structure of a part. Carburizing, nitriding, induction hardening and quench-tempering are the most common methods.
Helical Gears: A cylindrical gear with teeth cut on an angle (helix angle) to the axis. Smoother and quieter than a spur gear at the cost of axial thrust.
Hobbing: A gear-cutting process using a hob (a worm-shaped cutter) that generates teeth by continuous rolling action. Wolfer hobs up to module m12.

I

4 terms

Induction hardening: A localized heat-treatment process that uses electromagnetic induction to heat a part's surface. Suitable for journal bearings and selectively hardened gear teeth.
Internal gear: A gear with teeth cut on the inside of a ring. Meshes with an external gear (pinion) inside it; used in planetary reducers and ring-gear drives.
Involute: The standard tooth-profile geometry used in modern gears. Maintains a constant velocity ratio and tolerates small variations in center distance.
ISO 1328: International gear-accuracy standard. Classes 0 (highest) to 12 (lowest). Wolfer routinely produces Class 5–8.

J

1 term

JIS B 1702-1: Japanese gear-accuracy standard, used by Japanese OEM customers and their Chinese subsidiaries. Maps closely to ISO 1328.

K

2 terms

KISSsoft: A commercial gear-design and calculation software. Wolfer accepts KISSsoft design output as a manufacturing input for non-standard module or pressure-angle gears.
Klingelnberg: German manufacturer of gear-inspection and bevel-gear-cutting equipment. The "Klingelnberg-type" gear inspection center at Wolfer measures pitch, profile, lead, and runout in one setup.

L

2 terms

Lead error: Deviation of the actual tooth-trace from the theoretical line across the face width. One of the four core parameters on a gear inspection report.
Locking Assemblies: A shaft-hub connection that uses a wedging or shrink action (taper bushing, shrink disc) to grip a shaft without keys. Eliminates backlash.

M

2 terms

Material certificate: A document from the steel mill stating the chemical composition and mechanical properties of a batch of steel. Wolfer ships EN 10204 3.1 certificates by default.
Module (m): The pitch diameter divided by the number of teeth. The fundamental sizing parameter of a metric gear. Wolfer hobs up to m12.

N

1 term

Nitriding: A surface-hardening heat-treatment process that diffuses nitrogen into the part. Produces a very hard case with low distortion — suitable for precision gears that cannot be ground after heat treatment.

P

7 terms

Pinion: The smaller of two meshing gears. In a rack-and-pinion drive, the pinion is the rotating gear that engages the linear rack.
Pitch circle: The theoretical circle on which the kinematics of a gear are defined. The point of contact between two meshing gears is on the pitch circle.
Pitch diameter: The diameter of the pitch circle. The product of module × number of teeth (metric) or number of teeth ÷ diametral pitch (imperial).
Pitch error: Deviation of the actual tooth spacing from the theoretical spacing. One of the four core parameters on a gear inspection report.
Pressure angle: The angle between the line of force on the tooth and the tangent to the pitch circle. Standard values are 20° (most common) and 14.5°.
Profile error: Deviation of the actual tooth flank from the theoretical involute curve. One of the four core parameters on a gear inspection report.
Profile shift: A deliberate radial offset of the gear cutter from the standard position, used to avoid undercut on low-tooth-count pinions or to fine-tune center distance.

Q

1 term

Quench-temper: A two-step heat-treatment process: rapid quenching to harden, then tempering at a lower temperature to relieve brittleness. Used for through-hardened transmission components.

R

3 terms

Gear Racks: A linear gear — effectively a gear of infinite radius. Meshes with a pinion to convert rotary motion to linear motion. Wolfer's racks reach module 12 and lengths over 2 m.
Runout: The total indicator reading of a rotating part. For gears, the radial runout of the pitch circle is one of the four core inspection-report parameters.

S

8 terms

Sintered gear: A gear made by compressing metal powder and sintering it. Lower precision than cut-and-ground gears; common in low-cost consumer applications. Not a Wolfer product line.
Spiral Bevel Gears: A bevel gear with curved teeth. Smoother and quieter than a straight-bevel gear at the cost of more complex cutting machinery.
Spline: A shaft with longitudinal ridges that mate with corresponding grooves in a hub. Transmits torque without slip and allows axial sliding.
Spur gear: A cylindrical gear with teeth parallel to the axis. The simplest and most common gear type.
Sprockets: A toothed wheel that engages a chain. Used in chain drives where positive engagement (no slip) is required.
Stainless steel: A corrosion-resistant steel alloy containing chromium. Common grades for Wolfer parts: SUS304 (general), SUS440C (high hardness), 17-4 PH (high strength).
Surface roughness: A measure of surface texture, specified by parameters such as Ra (arithmetic average) and Rz (peak-to-valley). Measured with a contact profilometer; Wolfer uses Mitutoyo SJ-410.
Timing Belt Pulleys: A toothed pulley designed to engage a toothed (timing) belt. Provides positive engagement at high speed without slip.

T

6 terms

Taper Bushings: A locking-assembly variant where a tapered split bushing is wedged into a tapered hub bore by axial screws. Compact and reusable.
Timing belt: A toothed belt that engages a synchronous pulley. Provides positive engagement without slip; common in linear motion stages and printing machinery.
Tolerance class: A designation indicating the precision grade of a manufactured feature. For gears: ISO 1328 Class 0–12, DIN 3962 Class 1–12, AGMA Q1–Q15.
Torque Limiters: A coupling that disengages or slips when a preset torque is exceeded, protecting the driveline from overload. Available in friction or ball-detent designs.
Tooth thickness: The width of a gear tooth measured along the pitch circle. Controlled tightly to achieve specified backlash.
Through-hardened: A part that has been heat-treated to a uniform hardness throughout, rather than a hardened case over a softer core. Used where moderate hardness and high toughness are both required.

W

1 term

Worm Gears: A gear set consisting of a worm (screw-like driver) and a worm wheel. Produces high reduction ratios in a compact envelope but with lower efficiency than helical sets.

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ISO 1328 Class 5 vs. AGMA Q12

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