# Rexnord MB2108 ZB2000 | MROSupply.com - MROSupply.com ***Rexnord MB2108 1 1/2" Mounted Spherical Roller Bearing, Fixed Cast Iron 3-Bolt Round Flange Block, Single Setscrew Locking Collar, Spring Loaded Heavy Contact Seal*** ## Product details: - Catalog number: 10418438 - SKU: 504468 - Price: ***$515.30*** Each - Shipping: ***FREE SHIPPING*** ON ORDERS OVER $100 - Brand: [Rexnord](https://www.mrosupply.com/brands/rexnord/) - Category: - [3-Bolt Flange](htts://www.mrosupply.com/bearings/mounted-bearings/mounted-roller-bearings/flanged-mounted-bearings/3-bolt-flange/) - [Flanged Mounted Bearings](htts://www.mrosupply.com/bearings/mounted-bearings/mounted-roller-bearings/flanged-mounted-bearings/) - [Mounted Roller Bearings](htts://www.mrosupply.com/bearings/mounted-bearings/mounted-roller-bearings/) - [Mounted Bearings](htts://www.mrosupply.com/bearings/mounted-bearings/) - [Bearings](htts://www.mrosupply.com/bearings/) - Unit of measure: each - Weight: 6.700 lb - UPC: 698210621520 - Technicall support: contact supplier for technical support on 800-626-2120 ## Product images: - https://static.mrosupply.com/images/noimage.webp ## Product attributes; - Ability to Relubricate: Yes - Available end cap: DTC4 - Available End Cap: DTC4 - Available Seal Type: K Light Contact Lip Seal; M Spring Loaded Heavy Contact Lip Seal (Buna and Viton); Z Clearance Seal; G Triple Lip - Bearing Brand: REX ROLLER BEARING - Bolt circle radius (in): 2 1/2 in - Bolt Circle Radius (in): 2 1/2 in - Bolt hole circle diameter (in): 5 in - Bolt Hole Circle Diameter (in): 5 in - Bolt Size (in): 1.5 in - Bore length (in): 2 7/8 in - Bore Length (in): 2 7/8 in - Bore size (in): 1.5 in - Bore Size (in): 1.5 in - Cage Material: Engineered Polymer - Clearance: C3 STANDARD - Distance between bolt holes (in): 4 21/64 in - Distance Between Bolt Holes (in): 4 21/64 in - Fixed vs. Expansion: Fixed - Foot Height (in): 0.63 - Grease Fitting Thread Size: 1/8 NPT - Height: 6.63 - Housing Cast Face to Outermost Bearing Face (in): 0.69 - Housing coating: Powder coated - Housing Coating: POWDER COATED - Housing construction: Solid - Housing Construction: Solid - Housing material: Cast iron - Housing Material: Cast Iron - Housing Outside Diameter (in): 6.25 - Housing style: Flange block - Housing Style: Flange Block - Housing type: Flange, Three Bolt - Housing Type: Flange, Three Bolt - Inner Ring Outside Diameter (in): 1.745 - Insert: 2108U - Length: 6.63 - Length Through Bore (in): 2.88 - Locking collar outside diameter (in): 2.31 - Locking device kit: SC4 - Locking Device Kit: SC4 - Locking Type: Single Set Collar - Lubrication type: EXXON RONEX MP STD - Lubrication Type: EXXON RONEX MP STD - Maximum Speed (RPM): 3300 rpm - Maximum Temperature (C): 107 - Maximum Temperature (F): 225 - Microlock kit: ML2 - Misalignment Capability: ±2.0° Misalignment - Dynamic - Misalignment Type: Dynamic - Mounting bolt size (in): 1/2 in - Mounting Bolt Size (in): 1/2 in - Net Weight: 6.70 - Overall Length (in): 6.25 - Overall width: 6.25 - Primary seal: Buna spring loaded lip seal - Primary Seal: BUNA SPRING LOADED LIP SEAL - Radial Dynamic Load Capacity (lb): 19860 lb - Radial Static Load Capacity (lb): 20900 lb - Retainer material: Engineered Polymer - Retainer Material: Engineered Polymer - Rolling element: Spherical Roller - Seal kit: MS4 - Seal type: Heavy Contact Seal - Setscrew torque (in-lbs): 325 - Size code: 4 - Size Code: 4 - Standoff distance (in): 0.03 - Unit of dimension: in - Unit of Dimension: IN - Vibration frequency fundamental train: 0.0070 cps - Vibration Frequency Fundamental Train: 0.0070 cps - Vibration frequency inner ring defect: 0.1445 cps - Vibration Frequency Inner Ring Defect: 0.1445 cps - Vibration frequency outer ring defect: 0.1055 cps - Vibration Frequency Outer Ring Defect: 0.1055 cps - Vibration frequency roller spin: 0.0499 cps - Vibration Frequency Roller Spin: 0.0499 cps - Volume: 0.713 - Volume unit: GLL - Volume Unit: GLL - Weight unit: LB - Width: 3.75 ## Product documents / software: - [Rex Mounted Roller Bearings Installation Instructions](https://documents.mrosupply.com/product_documents/23/63/2363892/6ddc7fe1403d4227d36d1cb21d07ffff0b45a555_lA7yTlb.pdf) - [Rex Mounted Roller Bearings Installation Instructions](https://documents.mrosupply.com/product_documents/85/76/857687/BR3-001_manual.pdf) - [Rexnord Bearings Catalog](https://documents.mrosupply.com/product_documents/58/93/5893723/5c878e5c94dc5c3d338a775129f99b4f092be791_xnS4NzU.pdf) - [Rexnord Bearings Catalog](https://documents.mrosupply.com/product_documents/85/80/858069/BR101-100EN_catalog.pdf) ## Product's reviews: - Mechanic - Great service and fast shipping and great quality of product. - Good orice - This stump grinder wheel bearing is expensive and I need two each time I change them. Best price I found anywhere and free shipping here at MRO Supply - Great service-fast shipping - Awesome service. I would highly recommend doing business with MRO! Price was cheapest anywhere - Rexnord idler pulley - Great pricing and fast shipping A +++++++++ ## FAQ: - How do I read a Rexnord (Rex) spherical roller bearing part number like ZA2115?: Read a Rex number as seal, housing, series, bore. In ZA2115, Z is the clearance seal, A a fixed 2-bolt pillow block, 2 the 2000 series and 115 the bore, 1 15/16 in (first digit inches, last two sixteenths). Other seal letters are K light contact, M spring loaded heavy contact and G triple lip. Housing codes include B 4-bolt flange, BR round flange cartridge, MC cartridge, EP Type E pillow block, EF Type E flange, F flange and T take-up. A trailing F means a 4-bolt pillow block base (ZA2307F), MM a metric bore (ZEP2045MM) and Y a redesigned shaft size that does not interchange with the older unit. - What is the difference between the Rex 2000, 3000, 5000, 6000 and 9000 series?: The series digit sets how the bearing locks to the shaft, and with it the duty level. 2000 uses a single setscrew collar (normal duty, simplest and cheapest), 3000 an eccentric Twist Lock collar (medium duty, extra holding power), 5000 a double setscrew collar (heavy duty), 6000 the Shurlok tapered adapter (heavy duty, full bore contact, easily removed) and 9000 a tapered adapter sleeve (extra heavy duty). Bores: ZA2000 covers 3/4 to 4 in, ZA5000 1 7/16 to 4 in and ZA6000 1 7/16 to 3 15/16 in. On take-up blocks a frame size code comes before the series digit, so ZT62115 is a 2000 series take-up, not 6000. - Which Rexnord roller bearings are fixed and which are expansion?: An S after the housing letters marks an expansion unit (Rexnord calls it floating), where the insert can move axially in the housing to absorb shaft growth: ZAS2115 is the expansion version of the fixed ZA2115, and the same applies to MPS, ZPS, ZBS, ZFS and ZAFS codes. Rex 2000 series units give a total of 3/8 in of expansion travel. Usual practice is one fixed bearing per shaft to locate it and expansion units at the other positions. Auxiliary cap kits are specific to fixed or expansion units: AS10307 is an open cap kit for 3 7/16 in expansion units, size code 10, in the 2000, 3000, 5000 and 9000 series. - What seal options do Rex mounted roller bearings come with?: Rex spherical roller bearings come with four seal types, and the first letter of the part number (after any A or B end cap prefix) tells you which: Z is the all metal clearance seal (ZA2115), K a single lip light contact seal (KA2307), M a spring loaded heavy contact seal (MA2107) and G a triple lip seal (GBR2315G). A V suffix on an M seal unit means Viton seal material for higher temperatures (AMA2207V). Rexnord states the seals are field interchangeable, so a unit can be changed from clearance to contact seals without replacing it. All Rex units allow a total of 4 degrees of misalignment, and auxiliary end caps can be added for extra protection. - How do I order a Rexnord roller bearing with end caps, or a replacement insert?: Factory end caps are coded into the part number. A prefix A means two open auxiliary caps (AMA2107) and B one open cap on the housing side and one closed cap on the cover side (BMA2108, BZEP2115), used where the shaft ends at the bearing. A single cap is a suffix instead: A one open cap (MB2115A), C a closed cap on the housing side (MEP2200C). Caps also come as kits, for example B10 is a closed cap kit for fixed units in size code 10 of the 2000, 3000, 5000 and 9000 series; 6000 series units take their own adapter cap kits. Unmounted replacement inserts carry a U suffix: 2215U is a 2 15/16 in 2000 series insert. - What bore sizes are available for 3-bolt flange bearings?: 3-bolt flange bearings are available in bore sizes ranging from 1/2 inch to 2 inches, with common sizes including 5/8" (UCFB-202), 3/4" (UCFB-204), 1" (UCFB-205), 1-1/4" (UCFB-207-20), 1-3/8" (UCFB-207-22), 1-7/16" (UCFB-207-23), and 1-3/4" (UCFB-209). Custom sizes larger than 2 inches are available through manufacturers. - What is the difference between set screw and eccentric collar locking?: Set screw locking uses two set screws spaced 120 degrees apart to secure the bearing onto the shaft, suitable for low-to-moderate speed applications. Eccentric collar locking uses an offset design to create a clamping force that strengthens during rotation and must be locked in the direction of shaft rotation to prevent loosening. - What is a 3-bolt flange bearing?: A 3-bolt flange bearing (UCFB series) is a mounted ball bearing unit with a triangular cast iron housing featuring three bolts for mounting. The housing contains a self-aligning ball bearing that compensates for minor shaft misalignment while supporting radial loads in industrial applications. - Are 3-bolt flange bearings sealed and regreasable?: Most 3-bolt flange bearings feature dual rubber lip seals with flinger rings on the inner race to deflect contaminants away from the bearing. Standard models come pre-lubricated and include a grease fitting, allowing for periodic relubrication without disassembly during maintenance intervals. - What are typical applications for 3-bolt flange bearings?: 3-bolt flange bearings are used in conveyors, fan and blower assemblies, food processing equipment, construction machinery, and HVAC systems. Their self-aligning design and sealed housings make them ideal for dusty or moist industrial environments where maintenance access is limited. - How do dynamic and static load ratings differ for flanged mounted bearings?: Dynamic load rating applies to continuous rotation with varying loads, while static load rating represents the maximum load the bearing can handle without permanent deformation when stationary. Select a bearing whose ratings exceed your application's actual loads with an appropriate safety margin. - What critical dimensions must I verify when selecting a flanged mounted bearing unit?: You must specify the bore diameter (inner diameter), outer diameter, and bearing width, plus the flange outer diameter and flange width for proper housing fit. These dimensions determine whether the bearing will seat correctly and handle the intended loads without interference. - What mounting and locking mechanisms are available for flanged mounted bearings?: Common locking methods include set screws, eccentric collars, and adapter sleeves, each suited to different shaft sizes and mounting requirements. Your choice depends on the shaft diameter tolerance and whether you need quick-change capability. - How does maximum permissible speed affect flanged bearing selection?: Maximum permissible speed depends on bearing size, load, and sealing type; exceeding it causes excessive heat generation and lubricant breakdown. Verify the bearing's speed rating against your actual RPM before selection, accounting for any speed fluctuations in your drive system. - What sealing options protect flanged mounted bearing units from contamination?: Flanged bearing housings offer various sealing configurations—open designs, contact seals, and non-contact shields—to match your environment's contamination risk. Higher-protection seals increase friction and heat generation, so choose the minimum seal level your application requires. - What's the difference between 2-bolt and 4-bolt flange mounts?: 2-bolt (diamond) flanges fit tight spaces and light-to-moderate loads. Switch to 4-bolt (square) flanges for cantilevered (overhung) loads, torque reversal, or shafts over 50mm—the extra bolts distribute load more evenly and resist side thrust better. - What lubrication schedule should I follow?: Use the bearing manufacturer's recommended grease grade and relubricate at intervals matched to your speed and load—heavy-duty applications may need monthly service, while light-duty runs can extend to 6–12 months. Over-greasing creates drag and heat; under-greasing causes metal-to-metal contact. Wipe off excess grease to prevent contamination. - What's the difference between pillow block and flange mounted bearings?: Pillow blocks mount parallel to the shaft (shaft runs horizontally along the base), while flange blocks mount perpendicular to the shaft (shaft extends out from the face). Choose pillow blocks for shafts that are level with your mounting surface; choose flange blocks when the shaft is perpendicular to your mount point. - How do I select the right bearing size and load rating for my application?: Match the bore diameter to your shaft size, then verify the dynamic load rating (C) exceeds your expected radial load. For radial loads, use C ≥ 3× your maximum load as a conservative starting point. Check speed rating against your RPM—pillow blocks typically handle 3,000–4,000 rpm while flange units can push 5,000+ rpm depending on bolt strength and bearing series. - How should I install and align a mounted roller bearing?: Align the bearing housing parallel to the shaft using a straightedge or dial indicator—misalignment is a leading cause of premature wear. Tighten mounting bolts in a cross pattern to seat the housing evenly. Use a soft mallet to tap the bearing unit into place; never force it. Check alignment after installation. - How often should I grease a mounted bearing?: Use the formula (OD in mm) × (Width in mm) × 0.005 = grams for periodic relubrication of the bearing element only; initial housing cavity fill is separate and should be 30–50% of free volume. Over-greasing damages seals and generates excess heat—stick to the calculated quantity and recommended relubrication schedule. - How do I install a mounted bearing correctly?: Verify your shaft diameter is within the bearing bore tolerance (consult the NSK or SKF datasheet), then secure the bearing to the mounting surface using the specified bolt torque and engage the locking collar or set-screw on the shaft to prevent axial slip. Hand-rotate the shaft through several complete turns with a dial indicator, laser alignment tool, or feeler gauge to confirm smooth operation and proper shaft runout within spec. - What are the main types of mounted bearings?: Mounted bearings come in four main forms: pillow blocks (flat-base, shaft parallel to mounting surface), flange mounts (perpendicular shaft, available in 2-bolt and 4-bolt variants with different radial ratings), hanger bearings (overhead support for long horizontal shafts), and take-up frames (adjustable center-distance units for belt or chain drive tensioning). Select based on your shaft orientation, load direction, and space constraints. - When should I replace a mounted bearing?: Replace based on condition: vibration signature analysis or ultrasonic emission (detected with a hand-held meter) indicates wear hours or days before audible noise appears, and is the actionable MRO signal. Other replacement triggers include continuous operation above 80°C housing temperature, visible grease leakage, or reaching the manufacturer's service interval for your duty cycle. Scheduled relubrication and temperature monitoring extend service life significantly — replacement is a last resort, not preventive maintenance. - What temperature should a mounted bearing run at?: Monitor housing surface temperature (the standard MRO measurement point): 40–65°C is normal, 70–75°C warrants investigation of misalignment or over-greasing, and 80°C requires immediate shutdown. The inner race runs 15–30°C hotter than the housing surface, so an 80°C housing reading means lubricant degradation is accelerating and the bearing requires emergency diagnosis. - How do I choose the right bearing for my application?: Bearing selection depends on five key factors: 1. Load Type and Direction — Determine whether your application has radial loads (perpendicular to shaft), axial loads (along the shaft), or combined loads. Deep groove ball bearings suit primarily radial loads; tapered roller bearings excel at combined loads; thrust bearings handle pure axial forces. 2. Rotational Speed — Ball bearings support higher speeds with lower friction. Roller bearings are better for medium-speed, heavy-load applications. Verify bearing speed ratings against your operating RPM. 3. Load Capacity — Select a bearing with adequate load capacity for your application. Basic dynamic load rating (C) and basic static load rating (C₀) determine how much load the bearing can safely carry. 4. Lubrication Requirements — Choose between grease and oil lubrication based on speed, temperature, and load. High-speed or high-temperature applications typically require oil circulation; lower-speed applications can use grease. 5. Precision and Rigidity — Evaluate your application's tolerance for runout deviation. High-precision applications require tighter tolerances and higher-grade bearings. - What is a bearing and what does it do?: A bearing is a mechanical component that enables smooth rotational or linear motion by reducing friction between moving parts. Bearings support loads and facilitate the transfer of forces between moving elements, preventing direct metal-to-metal contact that would cause wear and heat buildup. Rolling element bearings contain balls or rollers that rotate within races (raceways) to minimize friction. Common types include ball bearings (used for moderate loads and high speeds), roller bearings (used for heavy loads at medium speeds), and angular contact bearings (designed for combined radial and axial loads). Bearings are essential in industrial equipment including motors, pumps, compressors, gearboxes, turbines, and conveyor systems. - How do I choose the right type of bearing for my application?: Start with the load and how it’s applied. You need to know if you’re dealing with radial loads, axial loads, or a mix of both. Then look at speed, operating environment, and space constraints. For example, ball bearings are great for high speed and lighter loads, while roller bearings handle heavier loads but usually at lower speeds. If there’s contamination, moisture, or heat involved, you may need sealed bearings or specific materials. In most cases, the right choice comes down to matching load type, speed, and environment to the bearing design. - How should I maintain and lubricate bearings?: Lubrication Importance — Improper lubrication causes over 40% of bearing failures. Proper bearing lubrication prevents friction damage, dissipates heat, protects against corrosion, and acts as a barrier against contaminants (dust, moisture, debris). Lubrication Selection — Choose between grease and oil based on: - Grease: Suitable for low-to-medium speed, sealed bearings, and applications without continuous circulation. Easier to apply and retain. Common for motors, household appliances, and sealed units. - Oil Mist or Circulating Systems: Better for high-speed applications, high-temperature environments, and heavy-load machinery where heat dissipation is critical. Best Practices: 1. Map all lubrication points and create a maintenance schedule. 2. Use the correct lubricant type and viscosity grade specified by the bearing manufacturer. 3. Store lubricants in sealed, labeled containers away from moisture and contaminants. 4. Monitor bearing temperature and vibration; unusual heat or noise may indicate inadequate lubrication or bearing wear. 5. Replace bearings before reaching L10 life if contamination or lubrication failure is detected. - What is bearing life (L10) and how does it affect my equipment maintenance?: L10 Life Definition (ISO 281) — L10 is the basic rating life at which 90% of a large group of identical bearings are statistically expected to survive under constant load and speed. It is calculated in millions of revolutions using the formula: L10 = (C/P)^p, where C is the basic dynamic load rating, P is the equivalent dynamic bearing load, and p is the life exponent (3 for ball bearings). Converting L10 to Operating Hours — To express L10 life in hours: L10h = (L10 × 10^6) / (60 × n), where n is rotational speed in RPM. For example, a bearing with L10 = 1,000 million revolutions operating at 3,600 RPM has approximately L10h ≈ 4,630 hours. Modified Life (L10a) — Actual bearing life also depends on lubrication quality, contamination, speed, temperature, and bearing accuracy. ISO 281 defines a modified life factor (a₁ × aISO) that adjusts the theoretical L10 for these real-world conditions. High-quality lubrication and proper maintenance can extend bearing life significantly; poor lubrication or high contamination reduces it. Why It Matters for Maintenance — L10 life helps you schedule preventive maintenance, budget for bearing replacement, and select bearings adequate for your duty cycle. - What are dynamic and static load ratings, and why do they matter?: Static Load Rating (C₀) — The maximum load a stationary or slowly rotating bearing can support without permanent deformation of its rolling elements or raceways. Defined by ISO 76 as the load producing 0.01% permanent deformation of the rolling element diameter. Static load capacity is the limiting factor when a bearing operates at very low speeds or remains stationary under heavy loads. Dynamic Load Rating (C) — The constant load a bearing can endure for a specified number of revolutions (the L10 life, at which 90% of identical bearings are expected to survive). Dynamic load rating determines how long a bearing will last under rotating or oscillating motion. ISO 281 defines the L10 calculation using the formula: L10 = (C/P)^p, where C is dynamic load rating, P is equivalent dynamic load, and p is the life exponent (3 for ball bearings, 10/3 for roller bearings). Why They Matter — Static load rating determines if a bearing can handle peak loads without permanent damage (even if not rotating). Dynamic load rating determines operational life. For high-speed applications, dynamic rating is critical. For low-speed or stationary loads, static rating may be the limiting factor. Always verify both ratings against your application's load profile. - What bearing materials are available and which should I use?: Standard bearing materials include: - Chrome Steel — Premium bearing steel used by SKF, NSK, Timken, and most manufacturers. Offers excellent hardness, fatigue resistance, and durability in standard industrial applications. Most common for ball and roller bearings. - Stainless Steel — Provides corrosion resistance for applications in wet, humid, or chemically corrosive environments. Used in food processing, marine, and pharmaceutical equipment. - Ceramic Hybrid Bearings — Combine steel races with ceramic rolling elements. Offer reduced friction, lower heat generation, and higher temperature capability. Used in high-speed, high-precision applications and aerospace. - Polymeric Bearings — Utilize fluoropolymer composites with embedded graphite or PTFE. Provide low friction in high-speed applications where lubrication film breakdown would be problematic. Material selection depends on operating environment (temperature, moisture, chemical exposure), speed, load, and precision requirements. Standard chrome steel bearings suit most industrial MRO applications.