PA66 Cage BK0408 BK0408TN Metric Size Needle Bearings 4x8x8mm

BK0408 and BK0408-TN are miniature metric single-row closed-end drawn cup needle roller bearings without inner ring, unified boundary dimension Fw=4mm needle assembly inner diameter, outer diameter D=8mm, total width C=8mm. BK series features integrated one-piece stamped steel outer cup with solid closed bottom cap, which achieves automatic axial positioning inside blind hole housings, eliminating extra snap rings, shaft shoulders and end caps to simplify miniature equipment assembly.

• BK0408: Standard stamped thin steel cage version, strong impact resistance, suitable for medium-speed light shock working environments;
• BK0408-TN: Equipped with glass fiber reinforced PA66 nylon TN cage, lighter weight, lower friction noise, better high-speed stability for clean, quiet miniature transmission scenes.

Dense needle roller arrangement provides high radial load capacity under ultra-slim radial cross-section. The matching shaft surface must be quenched to HRC60–64 and mirror superfinished to serve as inner raceway. This series only bears pure radial load, widely used for micro reduction gearboxes, miniature handheld power tools, small office equipment, textile micro tension rollers, automation tiny sliding components and lightweight toy transmission assemblies with extremely limited radial installation space.

Fw (Needle assembly inner diameter): 4 mm
Outer Diameter D: 8 mm
Overall Width C: 8 mm
Structure: Single row closed end drawn cup needle bearing, no inner ring
Outer Cup Material: GCr15 high-carbon chrome bearing steel
Standard Radial Clearance: CN normal clearance
Minimum chamfer r: 0.3 mm
Required matching shaft hardness: HRC60–64 mirror superfinishing

Cage Type: Stamped thin carbon steel cage
Dynamic Load Cr: 1760 N
Static Load Cor: 1370 N
Reference grease limiting speed: 22000 r/min
Oil lubrication limiting speed: 26000 r/min
Net Weight: 0.0016 kg

Cage Type: Glass fiber reinforced PA66 TN plastic cage
Dynamic Load Cr: 1540 N
Static Load Cor: 1070 N
Reference grease limiting speed: 28000 r/min
Oil lubrication limiting speed: 40000 r/min
Net Weight: 0.0018 kg
Complete dimensional drawings and full technical load data of two models are available upon customer request.

1. Integrated closed bottom cap self-locating design, directly pressed into blind hole housing without additional axial fixing parts, cut miniature equipment part count and assembly cost
2. Ultra-miniature slim radial cross-section greatly reduce equipment radial occupied space, perfect for micro compact transmission structural design
3. Two cage options (steel / TN nylon) match different working demands: steel cage for impact resistance, TN PA66 cage for ultra-low noise & high-speed operation
4. Compact dense needle layout delivers reliable radial rigidity and load capacity, stable continuous low-medium speed reciprocating operation
5. Lightweight TN nylon cage reduces rolling friction, lowers running noise and improves high-speed rotation smoothness without oil shortage failure easily
6. Customizable options include single RS rubber seal, C3 enlarged radial clearance, stainless steel anti-rust drawn cup, OEM laser marking and low-temperature lubricant filling

Effectively simplify micro blind hole housing machining and extend service life of miniature shaft-end transmission assemblies

This BK0408 / BK0408-TN miniature closed end needle roller bearing set is widely matched for the following micro light-duty industrial & civilian equipment:

• Micro miniature reduction gearboxes, tiny transmission box blind hole shaft end supporting assemblies
• Mini handheld power tools, small garden electric mini machinery rotary parts
• Office precision tiny equipment, textile micro loom tension sliding roller units
• Automation miniature linear sliding mechanisms and micro cam shaft positioning components
• Light model toys, small household electrical lightweight rotary sliding assemblies
• Aftermarket replacement spare parts for 4mm inner diameter miniature closed end drawn cup needle roller bearing equipment

Ideal dual-option compact high-speed micro bearing solution for blind hole shaft-end miniature transmission equipment

• 25 years of professional miniature BK series closed end drawn cup needle roller bearing manufacturing experience
• Two models fully dimensionally interchangeable with international standard BK0408 series bearings, consistent outer cup dimensional tolerance
• Complete OEM & ODM customized service supporting RS sealing, stainless steel shell and special clearance customization
• Full-process strict inspection: raw material hardness testing, deep drawing forming precision, cage assembly tightness and dynamic speed cycle testing before delivery
• Professional bearing engineering team provides micro blind hole housing tolerance and matching shaft hardness installation guidance within 24 hours
• Stable mass production assembly lines with preferential bulk wholesale price for long-term miniature equipment manufacturers

We focus on stable axial positioning, low noise performance and long-term win-win cooperation with global industrial buyers

• Raw material chemical composition and surface hardness inspection of GCr15 chrome bearing steel
• Precision deep drawing, trimming and forming processing for integrated closed end outer drawn cup
• Constant temperature heat treatment process to stabilize outer cup internal stress and enhance wear resistance
• Separate performance testing for two versions: steel cage impact durability, TN nylon cage high-speed noise & temperature resistance, radial clearance uniformity
• Uniform needle roller assembly inspection and separate dimensional & appearance re-inspection for each model before anti-rust packaging and shipment
• Every batch of bearings passes full sampling reciprocating cycle durability test to guarantee stable radial load operation in micro blind hole housings

If you need high-quality BK0408 steel cage and BK0408-TN PA66 nylon cage miniature closed end drawn cup needle roller bearings for micro gearbox and mini power tool equipment, send your inquiry to us directly.
You will receive full professional supporting services after submitting inquiry:

• Fast official factory quotation reply within 24 hours
• One-on-one micro blind hole housing tolerance & matching shaft hardness parameter matching guidance by professional bearing engineers
• Customized bearing solution suggestions including RS sealed variants and stainless steel anti-rust drawn cup options
• Competitive direct factory bulk wholesale price for mixed two-model combined bulk orders

Send your required purchase quantity of each model and equipment operating environment to obtain detailed formal quotation

Q1: What does suffix TN stand for in BK0408-TN?
A1: TN means glass fiber reinforced PA66 plastic cage, lighter, low friction and suitable for high-speed quiet operation.
Q2: What’s the core difference between BK0408 and BK0408-TN?
A2: Same overall dimensions; BK0408 uses steel cage with higher load capacity and impact resistance; BK0408-TN uses nylon cage for higher limit speed and lower running noise.
Q3: Can BK series bearings work without hardened ground shaft?
A3: Not recommended. Matching shaft contact surface must reach HRC60–64 quenching hardness with mirror finish to act as inner raceway and avoid rapid wear.