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.

  • 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.
  • 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.
  • 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 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.
  • 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).
  • 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.
  • 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.
  • 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.