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Mastering Crank Pins and Piston Pins

Motorcycle Crank Pins & Piston Pins | Precision Engineered Components

Motorcycle Crank Pins & Piston Pins

Precision Manufacturing for High-Performance Engines

Overview

The core of motorcycle engine performance lies on precision-engineered crank pins and piston pins. Our advanced manufacturing techniques and stringent quality standards ensure excellent durability, wear resistance, and performance under high stresses.

Key Specifications

  • Heat Treatment: Carburizing for enhanced durability and wear resistance.
  • Hardness: Surface hardness between HRC 59-65.
  • Outer Diameter Tolerance: -0.001 mm to -0.003 mm for perfect fit.
  • Length Tolerance: Precision-maintained for seamless integration.

Advanced Inspection Instruments

We utilize state-of-the-art equipment to maintain the highest precision standards:

  • Cylinder Measuring Machine (U.K. Taylor Hobson)
  • Surface Roughness Meter (U.K. Taylor Hobson)
  • Micro Hardness Meter
  • Rockwell Hardness Meter
  • Profile Projector
  • Metallurgical Microscope
  • Computer Servo-Control Materials Testing Machine
  • Contour Measuring Instruments

Inspection Parameters and Capabilities

Item Scope Instrument Capability
Outer Diameter -0.002 mm ~ -0.004 mm Outer Diameter Measuring Instrument ± 0.0005 mm
Length +0 mm ~ 0.20 mm Vernier Calipers ± 0.01 mm
Carburized Depth As per specification Micro-Hardness Gauge ± 0.02 mm
Surface Hardness HRA 80-84 / HRC 58-65 Rockwell Hardness Meter ± 0.1
Core Hardness HRC 30~45 Rockwell Hardness Meter ± 0.1
Surface Roughness Under Rz 0.8 / Ra 0.2 Surface Roughness Meter ± 0.0001 µm
Cylinder Less than 0.002 mm Cylinder Meter ± 0.01 µm
Straightness Less than 0.002 mm Cylinder Meter ± 0.01 µm
Carburized Structure Residual austenite < 8% Metallurgical Microscope Visual

Why Choose Our Pins?

Our crank pins and piston pins are crafted to deliver exceptional performance, reliability, and durability. With advanced surface treatments, rigorous quality control, and precision engineering, our components excel in high-performance engine applications.

Contact Us

For more information about our manufacturing capabilities or to discuss your specific requirements, please contact us.

KU/KUZ Needle Bearings for High-Load Engines

KU/KUZ Needle Bearings | High-Performance Engine Components

KU/KUZ Type Needle Roller Bearings

High-Performance Bearings for High-Speed, Heavy-Load Engines

Overview

KU/KUZ type needle roller bearings are designed for the big-end or lower-end bore of connecting rods in heavy-loading, high-speed engines. The cage of KU/KUZ type bearing offers higher rigidity, featuring a large and flat outer diameter surface to effectively reduce contact pressure between the cage and the inner race of the connecting rod's big end bore.

This design accommodates a greater number of needles compared to the KT type bearing, making it suitable for ultra-high-speed or heavy-load engine applications.

ku_kuz.jpg

Key Features

  • Heat Treatment: Carbonitriding treatment for superior hardness and wear resistance.
  • Hardness (Roller): HRC 60-66, providing durability under heavy-load conditions.
  • Dimensional Tolerance: Needle outer diameter tolerance precisely maintained at +0 / -0.002 mm.

Why Choose KU/KUZ Needle Roller Bearings?

KU/KUZ type needle roller bearings are engineered for extreme performance in high-speed and heavy-load engine applications. With a robust cage design, superior heat treatment, and precise tolerances, these bearings offer exceptional durability and reliability under demanding conditions.

Contact Us

For more information about our KU/KUZ type needle roller bearings or to discuss your specific requirements, please contact us.

KT Needle Bearing for Engine Crankshafts

KT-S Needle Bearing | High-Performance Engine Components

KT Type Needle Roller Bearing

High-Performance Bearings for Engine Crankshafts

Overview

The KT type needle roller bearing is specifically designed for the big-end or lower end bore of the connecting rod in engine crankshafts. This type of bearing operates eccentrically around the engine output shaft, with centrifugal forces significantly increasing at higher rotational speeds. Therefore, the structural strength of the cage requires special reinforcement.

The cage of the KT type bearing is made of SCM 415 chrome molybdenum alloy steel, which undergoes heat treatment and shot peening to enhance fatigue strength.

kt.jpg

Key Features

  • Heat Treatment: Carbonitriding treatment for superior hardness and wear resistance.
  • Hardness (roller): HRC 60-66, ensuring reliability under high-load operating conditions.
  • Dimensional Tolerance: Needle outer diameter tolerance precisely maintained at +0 / -0.002mm.

Why Choose KT Type Needle Roller Bearings?

KT type needle roller bearings are engineered for high-performance engine applications, combining advanced material treatments, exceptional hardness, and precise tolerances to meet the demands of high-speed and high-stress operations. Whether for motorcycles or other engines, KT type bearings deliver superior durability and reliability.

Contact Us

For more information about our KT type needle roller bearings or to discuss your specific requirements, please contact us.

KU vs. KT Bearings: Enhanced Rigidity and Performance

KU vs. KT Bearings: Enhanced Rigidity and Performance

KU vs. KT Bearings: Enhanced Rigidity and Performance

Compared with KT type bearing which applied on motorcycles, KU type bearing has higher rigidity than KT bearings. The cage’s flat and larger exterior surface help to reduce the contact stress between cage and race caused by the centrifugal force. The number of needle rollers of KU/KUZ cage can be 1-2 more than KT type at the same dimension. In all, such design is most suitable for engines with extremely high speed or high load.

The following photos show the difference between KT and KU type bearings:

KU Type Bearing KT Type Bearing

Connecting Rods Technology Overview

What Makes a High-Quality Connecting Rod?

A connecting rod is an engine part that connects a piston to a crankshaft in an internal combustion engine. For motorcycle engines, a high strength connecting rod is required to bear the combustion forces from the piston and transfer them to rotational torques to the crankshaft. Forged connecting rods, made of chromoly steel, are manufactured through a series of processes including hot forging, rough machining of planes and bores, heat treatment, and precise grinding of planes and bores.

Forged connecting rods process

A motorcycle connecting rod is especially important in motorcycle engines because the bore race has to be hard (HRC60) to resist abrasion from the crank pin and piston pin during high RPM operation. However, a hard material is brittle, which may cause connecting rod failure in the rod area. To avoid connecting rod breaking, the hardness in the rod area must be lowered to HRC35. This makes the material at the rod area more ductile, allowing the motorcycle engine to operate safely with a good connecting rod.

Motorcycle connecting rod bore roundness

Another important specification of a connecting rod is the roundness of the connecting rod bore. Roundness measures how closely the bore approaches a perfect circle. The bore diameter is measured at different angles, and roundness is the difference between the maximum and minimum of all the diameter measures. Generally, a qualified motorcycle connecting rod requires a roundness of 0.003mm for both the big-end bore and small-end bore. Therefore, achieving perfect bore roundness ensures the engine operates smoothly and greatly enhances the durability of the connecting rod.

Motorcycle Connecting Rod Heat Treatment

Motorcycle Connecting Rods: Characteristics and Heat Treatment

The characteristic of motorcycle connecting rod is that the bore race has to be hard (HRC60) to resist abrasion from crank pin and piston pin during high RPM operation. However, a hard material is brittle and it is easily to break. The hardness of rod area is necessary to lower down to HRC35 to avoid from connecting rod breaking by the brittle steel. The steel at rod area becomes ductile and then the motorcycle engine can operate safely.

Characteristic of a motorcycle connecting rod

To produce the perfect connecting rod which is hard at bore area and is soft at rod area, the heat treatment of connecting rod is the key process. The common material of motorcycle connecting rod is chromoly steel, SCM415 or SAE4118. SCM415 is a low-carbon steel. The carburizing heat treatment is applied to increase the connecting rod hardness. However, the carburizing heat treatment causes the whole connecting rod hardened to HRC60 including the rod area. The connecting rod is too brittle if we just apply carburizing heat treatment. There are two methods to produce soft rod area after carburizing heat treatment.

1. To apply partial annealing heat treatment on a carburized connecting rod:
Annealing is a heat treatment to increase ductility and reduce hardness of material. Usually, the material is heated above its recrystallization temperature, maintaining a suitable temperature with a proper time, and then cooling with proper temperature gradient. The black carbon is precipitated on the steel surface. Therefore, the rod area becomes black since it is annealed to lower the hardness.

Annealing type connecting rod

2. To apply copper plating layer to avoid from carburization:
A high density copper is plated on the rod surface before carburizing heat treatment. The copper layer can isolate the steel from carbon gas, therefore, the steel with copper layer will not be hardened. The copper on bore races are removed before heat treatment. At last, the bore race is hardened with hardness HRC60, and the rod area is protected by copper layer with hardness HRC35.

Copper type connecting rod

Question: Which heat treatment method is better for a connecting rod?

The biggest difference between annealing type connecting rod and copper type connecting rod is the core hardness at rod area. The carburizing heat treatment will harden the steel surface around 1.0mm, which is called the carburizing depth. The hardness below carburizing depth becomes uniform with hardness HRC35 which is called core hardness.

For copper type connecting rod, the core hardness at rod area is HRC35 which is the same as the core hardness of carburizing heat treatment. However, for annealing type connecting rod, the core hardness at rod area decreases down to HRC25 because of the annealing heat treatment. As a result, the copper type connecting rod has better stiffness or strength than annealing type connecting rod. The power loss of copper type connecting rod is less than annealing type connecting rod.

Enhancing Motorcycle Connecting Rods: Material Composition and Strength Analysis

Motorcycle Connecting Rod Materials and Heat Treatment

A motorcycle connecting rod is required to be hard (HRC60) at bore area, and it is required to be ductile at rod area. Therefore, the chromoly alloy steel is applied for the motorcycle connecting rod. For the traditional application, SCM415/SCM420 or 15CrMo4 is the most commonly used low-carbon alloy steel. After carburizing heat treatment, the surface hardness is increased to HRC60. The abrasion resistance is increased. Meanwhile, the strength is still good at core area.

Forged connecting rods process

SCM415 Material Composition:

(C)% (Si)% (Mn)% (P)% (S)% (Ni)% (Cr)% (Mo)% (Cu)%
0.13-0.18 0.15-0.35 0.6-0.85 ≦0.03 ≦0.03 ≦0.25 0.9-1.2 0.15-0.30 ≦0.3

For higher power engine or modified engine, the strength of SCM415 may be not enough. A higher strength nickel-contained chromoly alloy steel is used to replace traditional SCM415. Generally speaking, the more nickel dissolved in the steel, the higher ductility or the higher yielding strength it becomes. A popular nickel-contained chromoly alloy steel is SNCM220. The yield strength of SNCM220 is 10% higher than SCM415, then providing more strength and safety of connecting rods.

Material Yielding Strength (MPa)
SNCM220 762
SCM415 693

Ref: https://www.steel-grades.com/

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