Angular Contact Ball Bearings: Angular contact bearings can accept both radial as well as axial loads simultaneously and offer the best compromise between speed and rigidity in relation to loads acting upon the shaft/spindle. Due to their design they achieve extremely high speed factors (in excess of 2X106Ndm). Since duplex bearings are normally supplied in matched pairs (ground so the inner and outer stickouts under specific nominal axial loads, are identical). Therefore, they should not be, separated or used w/single bearings of other pairs. They can also accept pure axial loads that are best taken up by duplex, triplex, quadruplex and quintuple matched arrangements.
Preloading, (the amount will depend upon the original bearing stickout and load deflection characteristics) will provide a stiffer bearing system and prevent ball-skid (during high accelerations). To avoid off-loading, the applied preload in matched sets of “DB” or “DF”, is generally achieved via the use of spacers or by using another bearing in opposition to the first. “DT” arrangements can support considerable unidirectional loading; axially and radially. The preload is generally achieved through the use of springs.
The basic series’ are shown by the ISO numbering system; ISO18 71800 (hyper-light), ISO19 71900 (ultra-light), ISO10 7000 (extra-light) and ISO02 7200 (light). Contact angles are generally supplied in 15º and 25º. To accept greater axial stiffness, the higher (25º) contact angle needs to be considered, but at the expense of reduced speed and radial rigidity. In certain applications, where one needs to meet possible combined requirements of speed, radial and axial rigidity, mixed contact angles (as well as mixed sizes) can be utilized. Only in tandem arrangements must the bearings be identical.
Cylindrical Roller Bearings:
Compared to point contact angular contact bearings, line contact cylindrical roller bearings have higher load carrying ability and greater stiffness. Conversely, even when comparing against multiplex arrangements in angular contact ball bearings, cylindrical roller bearings have much lower limiting speeds. Generally, they are used for medium and large size machine tools and spindles in combination with angular contact ball bearings and where higher loads and stiffness are required.
•Single row (N1000K) ** are used as the floating bearing in conjunction with a fixed angular contact ball bearing.
•Double row (NN3000K) bear high radial loads rather than axial loads which is due to the design of removable or separable inner/outer rings. Both N1000K & NN3000K series, the inner rings have two ribs with a separable outer ring. When mounting the bearing, moving the inner ring axially will cause bore expansion thus changing the radial play, resulting in a preloaded bearing. The outer ring construction of one groove with three holes, allows for very efficient use of oil lubrication. For grease lubrication requirements, a running-in period is required to avoid possible heat buildup and possible other related failures.
**Double Direction Angular Contact Ball Bearings:
This series (2344 & 2347) is separable and comprised of two rings; one seating, one spacer, rolling elements and a cage. Generally, this 60º contact angle bearing is used in areas of high axial loading and used in high precision machine tool spindles where the angular contact thrust bearing abuts the tapered shaft seat of a double row cylindrical roller bearing. By changing width (via grinding) of the spacer ring, one can change the clearance and preload. Nominal outside diameters are the same as the corresponding of double row cylindrical bearing and are used together. However, there is a difference between the outer ring of the bearing and housing. Since double direction angular contact thrust ball bearings cannot withstand radial loads, these loads are borne by the double row cylindrical roller bearing (within the same application).
•Double direction angular contact thrust bearings are classified as belonging to 2344 series or 2347 series. The 2344 series is fitted with the small side of the tapered bore of NN3000K bearings. The 2347 series is fitted with the large side of the tapered bore of NN3000K bearings. An oil groove and three oil holes are located in the middle of the seating ring. By this way, both rows of balls and the cage can be easily lubricated by the unhampered flow of oil during rotation. The double direction angular contact thrust bearings offer high precision, high stiffness, lower operating temperatures, high speed and ease of assembly and dis-assembly.
**High Speed Angular Contact Thrust Ball Bearings:
As with the 2344 and 2347 series, the 70X2A/DB (30º) & 70X2B/DB (40º) bearings are predominantly used together with NN3000K series in applications such as machining centers and NC lathes, requiring high speed and high rigidity. In substituting 2344 and 2347 bearings, the 70X2A/DB (30o) & 70X2B/DB (40º) bearings are designed for back-to-back mode and have outer diameter tolerances same as the 2344 and 2347 series, as well as having same width dimensions. Therefore, by simply using the appropriate spacer, there is no need to remove (the more difficult-to-remove) shafts/housings when substituting these bearings for double direction thrust bearings.
Tapered Roller Bearings:
The single row 3200 series tapered roller bearings are used to sustain radial loads and unidirectional axial loads. Under radial loading, as the axial force component is transferred to the internal portion of the bearing, another tapered roller bearing is used in conjunction with the first. This allows for acceptance of large amounts of axial loads, but limiting speeds become lowered. Installing and or removing these bearings are made easier due to the inner and outer being separable.
Ball Screw Support Bearings (Single Direction Thrust Bearings)
The precision ball screw support bearing 7602 & 7603 contains a (heavy) 60o contact angle (same as the 2344 and 2347 series). Due to its characteristics of high precision, high speed ability, high stiffness in the axial direction, lower friction, long life and the ability to rapidly change speeds; (high to low), it is specifically used in the support of precision ball screws in NC machines, etc. Though specially aimed to sustain heavy, unidirectional loads, these bearings can also accept small amounts of radial loads as well. Generally, the bearings are used in pairs or multiplex arrangements, with matching practices same as the standard angular contact ball bearing.
Ball Screw Bearing Cartridge Units:
The ease of installing the support bearings becomes apparent, when as one single unit; housing (cartridge unit) and the accompanying support bearings; pairs, triplex or quadruplex arrangements becomes a relatively simple “task”. These cartridge units are manufactured to incorporate or match the corresponding bearing sets; BSDU…DF (pairs), BSTU…TFT (triplex) and BSQU…QFC (quadruplex)
Precision Locking Nuts:
To match the tolerances of the bearings and related mating parts, (cartridge units), two series of precision locking nuts are produced; KMA and KMB series.
Roller Bearings For Rotary Table Application
This bearing (YRT) is composed of two needle roller thrust bearings and a radial cylindrical roller bearing. The preloads are imposed in both axial and radial directions. The bearing is fixed in the assembly via the equally spaced holes in both inner and outer rings.
