The precision grades of honed tubes are mainly classified based on dimensional accuracy (tolerance grade), form accuracy (roundness, cylindricity), and surface roughness (Ra value). Their impacts on performance and applications are as follows:

Dimensional Accuracy

• High precision (e.g., IT7 grade): Features a small inner diameter tolerance, ensuring uniform fitting clearance with the piston and strong sealing performance. It is suitable for high-pressure hydraulic systems (such as aerospace servo cylinders), which can reduce leakage and improve power output.

• Low precision (e.g., IT9 grade): Has a relatively large tolerance, which may lead to poor fitting, easy oil leakage or vibration. It is only applicable to low-pressure scenarios (such as agricultural machinery cylinders).

Form Accuracy

• High roundness/cylindricity (error ≤ 5μm): The inner hole is smooth and straight, ensuring stable piston movement, reducing jamming and wear. It is suitable for precision motion equipment (e.g., feed cylinders of precision grinding machines).

• Low precision (error ＞ 20μm): Piston jamming may occur due to ovality or bending. It is only applicable to rough working conditions with low requirements for motion precision (e.g., cylinders of mining machinery).

Surface Roughness

• Low Ra value (≤ 0.8μm): The surface is smooth, featuring a small friction coefficient and strong corrosion resistance. It is suitable for high-cleanliness or high-frequency motion scenarios (e.g., medical equipment, food machinery).

• High Ra value (≥ 1.6μm): The rough surface is prone to wear, making it suitable for general industrial environments (e.g., cylinders of construction machinery).

Selection Recommendations

• High-pressure & high-frequency scenarios: Prioritize high-precision honed tubes (IT7 grade, Ra ≤ 0.4μm) to ensure sealing performance and service life.

• Cost-effective needs: Medium-low precision (IT8-IT9 grade, Ra 1.6μm) can meet regular load requirements.

• Special environments: For corrosive or high-cleanliness scenarios, honed tubes should be paired with corrosion-resistant materials (e.g., stainless steel) and low-roughness surfaces.