Frequently Asked Questions
PART NUMBERS AND DESIGNATIONS
TAPERED ROLLER BEARINGS
SPHERICAL ROLLER BEARINGS
ANGULAR CONTACT BALL BEARINGS
CLEARANCE AND PRELOAD
- Where is the nearest distributor or field sales person? Contact customer service at 1-800-323-2358 and they can put you in touch with the area sales representative or local distributor. Or, search for an NTN Authorized Distributor here [LINK TO: 3.0 – DISTRIBUTOR SEARCH].
- Does NTN have field engineering support? How do I schedule a visit? NTN does provide engineering field support to our customers. Contact your local NTN sales representative to arrange a visit.
- Load ratings seem to vary from manufacturer to manufacturer, is there a single method that can be used to compare like styles of bearings? Load ratings don't really vary from among manufacturers, the methods used to calculate load ratings is different. Some manufacturers use the ABMA standard, some use the US Industry standard, some use equivalent dynamic load calculations. In general if the internal design is the same the load ratings will be equivalent.
- What factors should be considered when choosing a bearing? All application data (loads, speeds, orientation, etc.), intended use, and environment.
- Where are specific bearing types manufactured, plant-by-plant? NTN has manufacturing plants in Asia, the Americas, and Europe that each produce a wide variety of product types. Contact NTN engineering for specific bearing inquires.
- Does NTN have any OEM programs similar to Timken? Contact the NTN Sales department.
- Are BCA parts/drawings going to be available? NTN is continuing to support the BCA product line. Individual prints can be requested through NTN engineering.
- What does the term "electric motor quality" mean? The term "electric motor quality" is freely used in describing bearings that meet a perceived "higher" level of quality than the standard ABEC-1 bearing. Contact NTN marketing for an Electric Motor Quality brochure.
- 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.
- What is the difference between LLB & LLU seals? 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.
- What is the nomenclature for Precision Bearings (P4, P5, Tolerances)? 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.
- What is the difference between T & D1 or what is the designation for an oil hole? D1 always denotes a relube feature (any bearing). T is old nomenclature for inch dimensioned bearing units housings with a relube feature.
- What is the designation for a bronze cage on cylindrical roller bearings? 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.
- What is the designation for a tapered bore on spherical roller bearings? 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.
- What does CE or C0 fit mean? 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.
- What does V1 mean at the end of the deep groove ball bearing nomenclature? 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.
- What does U3A mean at the end of the deep groove ball bearing nomenclature? 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.
- What does LD1NR mean? 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.
- 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.
- Are tapered bearings case-carburized? 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).
- Does NTN make tapered roller assemblies? 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).
- Does NTN make extra precision tapered roller bearings? 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.
- What is the recommended end-play for tapered roller bearings? 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.
- 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.
- Does NTN make sealed spherical roller bearings? 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.
- Does NTN make angular contact bearings? NTN makes a full line of standard and high-speed angular contact bearings.
- What is the designation for sets (pairs) on your 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).
- Does NTN make angular contact bearings with steel cages? NTN makes a selection of cage options, including steel for our angular contact bearings.
- What is back-to-back and face-to-face in 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.
- What is the difference between angular contact bearings and deep groove ball bearings? Deep groove ball bearings are a non-separable type bearing with the line connecting contact points of the inner ring, steel ball, and outer ring of 0º in the radial direction. They are designed to take mainly radial loads but can handle some axial load in either direction. Angular contact bearings are also a non-separable type. The line connecting contact points of the inner ring, steel ball, and outer ring creates an angle with the line drawn in the radial direction called the contact angle. Angular contact bearings 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.
- 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.
- Explain the difference between C3 and normal clearance? Clearance classes are established by ABMA. C3 is a clearance specification one class larger than "C Normal" (sometimes referred to as "C0" in deep groove radial ball bearings).
- Is there a chart that shows radial clearance ranges in both metric & inches? NTN does not generally publish clearance tables with inch dimensions.
- What is preload? 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.
- Is it safe to use a C3 fit in place of a standard fit? 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.
- What is the difference between ABEC-3 and C3? Does the fit get better going up to C4 or down to C2? 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.
- 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.
- What is good high temperature grease? NTN has close to 700 greases listed. To pick one for a specific application requires more application information.
- Which grease is best suited for most general bearings? 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.
- How much grease is too much? 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.
- What grease can be used when performing maintenance on mounted units? 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).
- What does each grease code identify? The grease code on a bearing number identifies the manufacturer, brand, and fill quantity.