Selection guides
Original engineering guides written from maintenance and procurement work — decode designations, choose clearance and seal options, and mount roller and angular-contact arrangements correctly, with data tables and explicit selection judgments.
Fundamentals & designation
-
Angular contact bearing pairs: DB, DF, DT arrangements and preload explained
Single angular-contact ball bearings are never used alone for radial loads. Learn back-to-back (DB/O), face-to-face (DF/X) and tandem (DT) mounting, contact-angle suffixes, and how built-in preload creates spindle stiffness.
Read guide →
-
Bearing clearance C2, CN, C3, C4: when looser is better
Radial internal clearance classes explained with the fit-and-temperature clearance budget: why interference fits and running heat consume play, when to specify C3 or C4, and when C2 is the correct choice.
Read guide →
-
How to read bearing numbers: designation system, bore codes and suffixes
Decode a bearing designation step by step: type digit, dimension series, the bore-code rule (code x 5 mm with the 00-03 exception table), and seal, clearance and cage suffixes across SKF and NSK.
Read guide →
Seals & internal clearance
-
6205 vs 6205-2RS: same 25×52×15 mm envelope, different duty
The open 6205 and sealed 6205-2RS share the ISO 15 envelope but differ in friction, limiting speed, lubrication and contamination protection. Here is how maintenance actually chooses.
Read guide →
-
Bearing clearance C2, CN, C3, C4: when looser is better
Radial internal clearance classes explained with the fit-and-temperature clearance budget: why interference fits and running heat consume play, when to specify C3 or C4, and when C2 is the correct choice.
Read guide →
Bearing types & mounting
-
Bearing fits: shaft and housing tolerance selection (k6, m6, H7, and when to use them)
How to choose shaft and housing fits for rolling bearings — the rotating-ring rule, common tolerance classes (j6/k6/m6/n6 for shafts, H7/J7/K7 for housings), how fits consume internal clearance, and the mistakes that cause fretting or cracked rings.
Read guide →
-
Angular contact bearing pairs: DB, DF, DT arrangements and preload explained
Single angular-contact ball bearings are never used alone for radial loads. Learn back-to-back (DB/O), face-to-face (DF/X) and tandem (DT) mounting, contact-angle suffixes, and how built-in preload creates spindle stiffness.
Read guide →
-
NU vs NJ vs NUP cylindrical roller bearings: which flange locates the shaft
Cylindrical roller designation letters encode which ring carries the integral flanges and therefore axial location. Compare NU, NJ, NUP, N and N designs with dimension examples and arrangement patterns.
Read guide →
Selection & procurement
-
Reference speed vs limiting speed: what bearing speed ratings actually mean
Why bearing catalogues list two different speed ratings — thermal reference speed and mechanical limiting speed — which one applies to your application, and the four factors (load, lubrication, clearance, cooling) that move the real limit.
Read guide →
-
Bearing cross reference: what full, partial and verify matches really mean
Same envelope is not the same as interchangeable. How the full / partial / verify cross-reference levels are assigned, when a full match still cannot be swapped, and a practical verification checklist before fitting an equivalent.
Read guide →
-
6205 vs 6205-2RS: same 25×52×15 mm envelope, different duty
The open 6205 and sealed 6205-2RS share the ISO 15 envelope but differ in friction, limiting speed, lubrication and contamination protection. Here is how maintenance actually chooses.
Read guide →
-
NU vs NJ vs NUP cylindrical roller bearings: which flange locates the shaft
Cylindrical roller designation letters encode which ring carries the integral flanges and therefore axial location. Compare NU, NJ, NUP, N and N designs with dimension examples and arrangement patterns.
Read guide →
-
Bearing clearance C2, CN, C3, C4: when looser is better
Radial internal clearance classes explained with the fit-and-temperature clearance budget: why interference fits and running heat consume play, when to specify C3 or C4, and when C2 is the correct choice.
Read guide →
-
How to read bearing numbers: designation system, bore codes and suffixes
Decode a bearing designation step by step: type digit, dimension series, the bore-code rule (code x 5 mm with the 00-03 exception table), and seal, clearance and cage suffixes across SKF and NSK.
Read guide →
More guides
-
Bearing grease selection and relubrication intervals: a practical guide
How to choose bearing grease — NLGI grade, base-oil viscosity, thickener type, temperature and water resistance — plus how to calculate relubrication intervals and grease quantity for open and shielded bearings.
-
Bearing failure modes: identify spalling, brinelling, false brinelling and the rest
A practical visual guide to bearing damage patterns — rolling-contact fatigue, brinelling, false brinelling, fretting corrosion, electrical pitting, smearing, contamination and edge loading — what each pattern looks like, its cause, and the correction that stops it coming back.