This page is available in English only. The language menu opens the home page in the other languages.

Guide

Why Housing Bore Tolerance Matters More Than You Think

A bearing rarely fails on its own. More often, the housing bore is too tight or too loose, and the bearing pays the price. This guide explains why the bore fit matters and what a good housing should offer.

Too loose: the outer ring creeps

When the bore is oversized, the bearing outer ring is not held firmly. Under load the ring can slowly rotate inside the housing — called creep or fretting. The result is wear on the housing seat, heat, and a bearing that fails long before its rated life.

Too tight: the internal clearance disappears

When the bore is undersized, pressing the bearing in squeezes the outer ring. That squeeze reduces the bearing internal clearance. With too little clearance, the bearing runs hot and can seize, especially at speed.

The H7 standard

For most pillow block and flanged housings, the bearing seat is machined to an H7 tolerance. H7 defines a small, controlled clearance band so the outer ring fits firmly without being crushed. It is an ISO standard, so the same letter means the same band whether the housing was made in China, Europe or anywhere else.

What to ask your supplier

Do not settle for "good fit". Ask for the actual tolerance class of the bearing seat, and how it is measured. A supplier who states the class and shows the measurement record is one you can work with. A supplier who cannot answer either has not controlled the most important dimension in the product.

We machine bearing seats to a stated tolerance class and measure every part before it ships. Send us your sizes and we will show you the numbers.