Bearing Selection Guide

How to select a plain bearing

Selecting a plain bearing (bushing) starts from three duty parameters — sliding speed v (m/s), surface pressure P (N/mm²) and operating temperature T (°C) — plus one maintenance decision: whether relubrication during service is possible. The combined PV limit (pressure × velocity, N/mm²·m/s) approximates the allowable frictional heating per unit area and must not be exceeded in continuous duty.

1. Define the duty — measure or calculate v, P and T at the bearing position, including oscillating movement and shock loads.
2. Fix the maintenance class — maintenance-free (PTFE sliding layer, graphite plugs, oil-impregnated sintered bronze), low-maintenance (grease pockets), or oil-fed with external supply.
3. Check the allowable limits — sliding speed, static and dynamic load, temperature range, and the combined PV limit. Pressure and speed limits are never simultaneously usable at their individual maxima.
4. Specify the mating shaft — hardness (HRC) and surface roughness (Ra) per material pair, as listed in the Compare view.

Frequently asked questions

What is a self-lubricating plain bearing?

A bushing whose sliding layer provides lubrication without external oil or grease — for example a PTFE composite layer, graphite plugs embedded in a bronze matrix, or oil stored in the pores of sintered bronze. Used where relubrication is impossible, undesirable, or contamination must be avoided.

What does the PV limit of a bearing mean?

PV = surface pressure (N/mm²) × sliding speed (m/s). It is a proxy for frictional heat generation per unit area. Every bearing material pair has an allowable PV limit for continuous duty; exceeding it accelerates wear even when pressure and speed are individually within their limits.

Which bushing types are maintenance-free?

PTFE composite bushings (steel, stainless-steel, bronze or lead-free backing), graphite-plugged solid bronze, graphite-filled wrapped CuSn8, solid-lubricant bimetal, graphite spherical plain bearings, and oil-impregnated sintered bronze (SAE 841 type) within its allowable PV range.

Which bushing suits high temperature or corrosive environments?

PTFE composite types cover −200…+280 °C, with stainless-steel backing for corrosive media such as chemical, pharmaceutical and food equipment. Graphite-plugged bronze covers −100…+300 °C. Verify the exact alloy and duty combination against the values in this guide.

What shaft specification is required?

Shaft hardness depends on the material pair — typically HRC 30–60 (HRC 30–45 for sintered bronze, 40–50 for PTFE composite, 45–55 for bronze types, 55–60 for spherical plain bearings) — with surface roughness Ra ≤ 0.8 µm (Ra ≤ 0.4 µm for PTFE composite and sintered bronze types). The Compare view lists the mating-shaft specification per bushing type.

Are metric and imperial units supported?

Yes. All limits convert between metric (mm, m/s, N/mm², °C, N/mm²·m/s) and imperial (in, ft/min, psi, °F, psi·ft/min) via the unit switch in the header.

This guide is a general engineering reference compiled from published catalogue data. Values are typical allowable limits for continuous duty, not guaranteed values for a specific application. Final selection must be validated under actual operating conditions.