TECHNICAL RESOURCES

FREQUENTLY ASKED QUESTIONS

At NTN, we get a lot of questions about our company, our engineering and our products. See below for answers to our most frequently asked questions.

General Questions
Part Numbers and Designations
  • What is the “4T-” prefix used for?
    The “4T-” prefix designates a tapered roller bearing that is made of a special grade of case-hardened bearing steel and is interchangeable with other manufacturers taper with the same part number.
  • The "LB" seal is a non-contact seal for reduced torque or higher speed requirements. The "LU" seal is contact seal for better grease contamination control, but the contact friction increases torque and lowers the limiting speed.
  • NTN follows the ISO precision tolerance classes of P0, P6, P5, P4 and P2, which are equivalent to ABMA classes ABEC 1, ABEC 3, ABEC 5, ABEC 7 and ABEC 9, respectively.
  • D1 always denotes a relube feature (any bearing). T is old nomenclature for inch dimensioned bearing units housings with a relube feature.
  • Usually a G1 suffix is used to indicate a bronze or brass cage in a cylindrical roller bearing. In rare applications an L1 type cage has been used as well.
  • A tapered bore on any NTN bearing (except tapered roller bearings) is a “K” (1 to 12 ratio) or “K30” (1 to 30 ratio) suffix.
  • NTN does not use "CE" or "C0". These are competitor terms for electric motor and normal internal clearances. Clearance does not indicate any type of fit.
  • For NTN "V1" stands for the first special variation on this basic part number. This suffix lettering does not indicate any specific features. A print will have to be reviewed to see the exact special features.
  • In a part number like 6313ZZC3/2AU3A the "U3A" can be a packaging code or specific customer identification code. This does not affect the bearing features.
  • LD1NR is the current suffix used on cylindrical outer ring bearing unit inserts. The "L" indicates it meets the new Japanese Industrial Specifications. The "D1" indicates it has a relube feature. The "NR" means it has a snap ring groove and snap ring on the outer diameter. This new suffix (LD1NR) will replace the older suffix D1NR on all future stock orders on this type of bearing.
  • All of these part numbers are from the bearing component of an eccentric locking collar bearing. The locking collar for all three would have EL205-100 marked on the side. Generally speaking, NTN stocks the bearing & collar together. The part number to search for would be UEL205-100, AEL205-100 or JEL205-100. This would provide you with both the bearing & the eccentric locking collar.
  • The TMB material is a special material developed for ball bearings by NTN for high load & long life applications. Part numbers that use this material have the '6' replaced by 'TMB' (i.e. 6206 becomes TMB206). Many end users commonly misread this part number as TM8206 which is a part number you will not find. When given a part number that starts with TM8... replace it with TMB... and continue your search.
  • Both of the callouts indicate that the housing comes with cast covers. C- is for an open cover. An open cover has a hole and seal to allow the shaft to continue past the bearing unit. CM- is a closed cover, which is a solid piece that closes off the bearing unit.
  • Any part that has the FG1 suffix at the end will come with food-grade solid lube. This suffix is used on both Sentinel series & standard NTN products. NTN uses a food-grade solid lube that is NSF H1 certified for use in all food production areas. If my Sentinel part does not have FG1 at the end will it have a food grade grease? Yes, ALL Sentinel series parts come filled with a food-grade grease that is NSF H1 certified. The FG1 just designates that the bearing comes with a food-grade SOLID LUBE.
  • Instead of using the specified arrangement, you can look at using Universal Flush Ground. The Universal Flush Ground is where the bearing is made & to be assembled in any arrangement (DB, DF or DT) & perform with no issues. The part number would begin at 7006CDB/GNP4 and end with 7006CGD2/GNP4 (NTN) or 7006CVDUJ74 (SNR).
Angular Contact Ball Bearings
  • Does NTN make angular contact bearings?
    NTN makes a full line of standard and high-speed angular contact bearings.
  • Paired arrangements for angular contact bearings are designated as “D2” (universal flush ground pair), “DB” (matched back-to-back pair), “DF” (matched face-to-face pair) and “DT” (matched tandem pair).
  • NTN makes a selection of cage options, including steel for our angular contact bearings.
  • Back-to-back (DB) or face-to-face (DF) are duplex arrangements of angular contact bearings (can also refer to taper bearings). Radial loads and axial loads in either direction can be accommodated by these arrangements. DB arrangements have a large spread between the bearing centers and should be selected when a rigid shaft is required for the application. DF arrangements have a very short spread between centers and should be applied when slight shaft misalignment is needed. The DB arrangement requires the inner rings to be clamped whereas the DF arrangement requires the outer rings to be clamped.
  • Deep groove ball bearings are a non-separable type of bearing with a line of action of the load contacts between the balls and the raceways with the bearing axis, commonly known as the contact angle, of 0º in the radial direction. They are designed to accommodate mainly radial loads and are suitable for high-speed operation and require little attention in service. The deep grooves enable light axial loads to be carried in either direction. They are available with shields and seals and can be supplied with the correct quantity and type of grease. Angular contact bearings are also a non-separable type. The line of action of the load contacts between the balls and the raceways form an angle with the bearing axis. This contact angle along with the inner and outer rings being offset to each other, allows the bearing to accommodate combined radial and axial loads. A single high shoulder on both the inner and outer rings enable a large number of of balls to be incorporated. This gives them very high loading capacity; they can accommodate relatively heavy axial loads in one direction in addition to radial loads. The larger the contact angle, the larger the axial loading capacity becomes.
  • Instead of using the specified arrangement, you can look at using Universal Flush Ground. The Universal Flush Ground is where the bearing is made & to be assembled in any arrangement (DB, DF or DT) & perform with no issues. The part number would begin at 7006CDB/GNP4 and end with 7006CGD2/GNP4 (NTN) or 7006CVDUJ74 (SNR).
Cylindrical Roller Bears
Mounted Unit Bearings
Spherical Roller Bearings
  • What is the difference between B-type spherical roller bearings and E-type?
    The B-type spherical roller bearing has asymmetric rollers guided by an inner ring center rib for better skewing control. E-type spherical roller bearing employs larger symmetric rollers for increased load capacity, fast becoming the industry standard. With the recent acquisition of SNR, NTN can provide more E-type spherical roller bearings than ever.
  • NTN makes a limited series of sealed spherical roller bearings, the WA22200 series, the MX-W22200, and various special part numbers. Please contact NTN engineering for more details.
Tapered Roller Bearings
  • Are your tapers the same as Timken?
    Are they interchangeable with Timken? All NTN-Bower tapered roller bearings, as well as NTN tapered roller bearings with the prefix “4T-” or “ET-,” are Timken interchangeable.
  • All NTN-Bower tapered roller bearings and NTN tapered roller bearings with the prefixes “4T-,” “ET-,” or “E-” are case-carburized. ISO-class tapered roller bearings with a "U" suffix and NTN tapered roller bearings not having a previously mentioned prefix will be through-hardened, although these tend to be larger sizes (8” outer diameter and larger).
  • Both NTN and NTN-Bower make 2- and 4-row assemblies, some of which can be found in the NTN-Bower catalog and the NTN Large Bearing catalog (2250/E).
  • NTN does make some select sizes of tapered roller bearings in high precision classes (i.e. ABMA classes -3, -0, -00 etc.). Please contact NTN engineering for more details.
  • End-play is application specific, or preset in the case of NA-type assemblies. The machine manufacturers recommendations should be followed. For new designs please contact NTN engineering.
Clearance and Preload
  • Does internal clearance affect the bearing precision (C3 vs. P3)?
    C3 is an internal clearance, or the amount of internal free space between the rolling elements and the raceways of a bearing. P3 does not exist. P6 is an ISO tolerance class equivalent to ABEC-3, or the accuracy the bearing is manufactured to. Clearance does not affect tolerance and tolerance does not affect clearance.
  • Clearance classes are established by ABMA.C3 is a clearance range one step larger than "C Normal" (sometimes referred to as "C0" in deep groove radial ball bearings).
  • NTN does not generally publish clearance tables with inch dimensions.
  • Preload is an initial load or "negative clearance" given to a bearing before or during operation. This results in the rolling element and raceway surfaces being under constant elastic compressive forces at their contact points. This has the effect of making the bearing extremely rigid so that even when load is applied to the bearing, radial or axial shaft displacement is minimized.
  • C3 is not a fit, it is an internal clearance. Fit is how tight or loose the shaft and housing hold the bearing in place. In most electric motor rebuild applications a C3 clearance can be used in place of a normal clearance. Contact NTN engineering for other applications.
  • ABEC-3 is an ABMA tolerance class. C3 is an internal clearance specification. Fit is the relationship between the bearing bore and outside diameters to the housing bore and shaft outside diameter. Tolerance, clearance, and fit are independent dimensions, although in some cases choosing a larger internal clearance can allow you to use a tighter interference fit. Please contact NTN engineering for details.
Grease
  • What are NTN’s standard greases?
    2AS (Shell Alvania 2S), 5K (Kyodo Yushi Multemp SRL) and 3AS (Shell Alvania 3S) are considered NTN standard greases. L627 (Mobil Polyrex EM) is the current standard grease for most aftermarket inventory. 5K is the standard for micro-size bearings. 3AS is the standard in bearing units.
  • NTN has close to 700 greases listed. To pick one for a specific application requires more application information.
  • The current NTN standard grease for unknown aftermarket applications is L627 (Mobil Polyrex EM). In most cases a quality general-purpose lithium- or polyurea-thickened grease will work.
  • For general applications a grease fill of 30% of the free space in the bearing is accepted as standard by most manufacturers. Slow speed applications in harsh environments (such as agricultural machinery) can sometimes require a larger fill. High speed applications (i.e. hand tools) can require a lesser fill. Check with NTN engineering for any special requirements.
  • Standard bearing unit inserts are pre-lubed with a lithium soap grease (Shell Alvania 3S). Relubrication should be a grease with the same soap/thickener (lithium).
  • The grease code on a bearing number identifies the manufacturer, brand, and fill quantity.
  • Unfortunately, just changing the grease will not allow a bearing to handle higher temperatures. A standard steel bearing can withstand temperatures up to 250F. If higher temperatures are needed, the bearing steel needs to also be changed to a temperature-stabilized grade (TS2, TS3, TS4).
  • Any part that has the FG1 suffix at the end will come with food-grade solid lube. This suffix is used on both Sentinel series & standard NTN products. NTN uses a food-grade solid lube that is NSF H1 certified for use in all food production areas. If my Sentinel part does not have FG1 at the end will it have a food grade grease? Yes, ALL Sentinel series parts come filled with a food-grade grease that is NSF H1 certified. The FG1 just designates that the bearing comes with a food-grade SOLID LUBE.
Seals