Needle Roller Bearings.

What are Needle Roller Bearings?

Needle roller bearings are compact rolling-element bearings that use long, thin cylindrical rollers, called needles, to carry high radial loads in a very small radial cross-section. Because the needles are at least four times longer than their diameter, they present a large contact area against the raceway, so a needle bearing supports far more radial load than a ball bearing of the same bore. That load density in a slim section makes them the default choice wherever a shaft needs support, but there is little room around it.

Accu supplies needle roller bearings in drawn cup construction, with open and sealed options to suit the operating environment. Typical uses include automotive and motorcycle transmissions, gearboxes, universal joints, camshaft and rocker assemblies, planetary gear sets, pumps and compressors.

How Drawn Cup Needle Roller Bearings Work

A drawn cup needle roller bearing has a thin-walled outer shell, deep-drawn and hardened from steel, that acts directly as the outer raceway. Inside it sits a single row of needle rollers. The bearing is pressed into a housing bore and runs on the shaft itself, so the shaft surface becomes the inner raceway. That is why the design is so compact: it removes the separate, thick inner ring a ball bearing needs.

For the bearing to reach its rated life, the shaft must be hardened and ground to a suitable finish. Where the shaft is soft or uneven, a separate inner ring is fitted to give the needles a hardened surface to run on. In an automotive universal joint, for example, four needle roller bearings sit in the yoke and let the cross rotate under high, fluctuating load while taking up almost no space, a job a ball bearing could not do in the same envelope.

Materials Needle Roller Bearings Are Made From

Every Accu needle roller bearing pairs a deep-drawn steel shell with hardened bearing-steel rollers:

• Steel - (ST14): the drawn cup outer shell, formed from ST14 (Nr. 1.0338) steel and hardened to serve as the outer raceway.
• Steel - (AISI 52100): the needle rollers, made from high-carbon chromium alloy bearing steel for hardness and rolling-contact fatigue resistance.

All sizes are supplied in a natural (uncoated) steel finish, ready to run with the appropriate lubricant.

Sizes and Types of Needle Roller Bearings Available

The range spans metric bore (inside diameter) sizes from 3 mm to 60 mm, with outside diameters from 6.5 mm to 68 mm, so most compact shaft positions are covered. Widths vary by series.

Type selection comes down to how the bearing sits on the shaft. HK bearings are open at both ends for a through-shaft location, while BK bearings are closed at one end to retain grease or seal against a shaft end. Double row (ZW) versions carry more radial load within a similar diameter.

Sealing is the second choice. Open, single seal (RS) and double seal (2RS) options let you balance lubricant retention against contamination exclusion. Where the shaft cannot be hardened, pair the bearing with a separate inner ring to provide a suitable raceway.

FAQs

Q: What are needle roller bearings used for?

A: Needle roller bearings suit compact, high-radial-load positions such as automotive and motorcycle transmissions, gearboxes, universal joints, camshaft and rocker assemblies, planetary gear sets, pumps and compressors.

Q: What is the difference between a needle roller bearing and a ball bearing?

A: A needle roller bearing carries far more radial load than a ball bearing of the same section because its long rollers make line contact, but it handles little thrust and needs more precise mounting.

Q: What are the different types of needle roller bearings?

A: Accu stocks drawn cup types with an open outer shell (HK series), a closed one end (BK series) and double row (ZW) versions, in open, single seal (RS) and double seal (2RS) options.

Q: What sizes do needle roller bearings come in?

A: Our needle roller bearing range covers metric bore (ID) sizes from 3 mm to 60 mm, with outside diameters up to 68 mm.

Q: What are the advantages of needle roller bearings?

A: They deliver high radial load capacity in the thinnest possible cross-section, saving space and weight while keeping rotational torque low.

Q: What are the disadvantages of needle roller bearings?

A: They carry only limited thrust (axial) load. They are sensitive to shaft hardness, finish and alignment. They also cope poorly with heavy shock loads.

Q: Do needle roller bearings need an inner ring?

A: They can run directly on a hardened, ground shaft; where the shaft is soft or uneven, fit a separate inner ring to provide a suitable raceway.

Q: How do you fit a drawn cup needle roller bearing?

A: Press the drawn cup squarely into a hardened housing using a fitting tool on the marked (stamped) end, keeping it square to avoid distorting the thin shell.

Bespoke Needle Roller Bearings Manufacture.

High precision, bespoke manufacture of Needle Roller Bearings to customer specification. State of the art facilities specialising in both small batch prototyping and large scale manufacture.