Insert Bearing

An insert bearing is the bearing part of a mounted unit: a sealed deep groove ball bearing with a spherical outside diameter and an extended inner race that locks to the shaft. FULI supplies UC, SB and SA inserts from Linqing, Shandong, on their own as replacements or as complete bearing units. The size table above lists every insert on this site with its bore, outside diameter and width. Below: how the three types differ, how to read the size, and which units each insert fits.

Insert bearing types: UC, SB and SA

The letters at the start of the number tell you how the insert locks to the shaft and how wide it is. The bore and outside diameter of a given size code stay the same across the three types; the widths do not.

Type	Locking	Example	Bore d (mm)	OD D (mm)	Inner ring width B (mm)
UC	Two set screws in a wide inner ring	UC205	25	52	34.1
SB	Set screw in a narrower inner ring	SB205	25	52	27
SA	Eccentric locking collar	SA205	25	52	21.5 (31 across the collar)

UC inserts are the standard choice for UCP, UCF and UCFL units. SB inserts are shorter along the shaft than UC inserts of the same size. SA inserts lock by turning the collar in the direction of rotation and then tightening the collar screw, so they are normally used on shafts that turn one way.

Insert bearing range and series at FULI

On this site the UC 200 series covers 12 to 70 mm shafts (UC201 to UC214), and the UC 300 series has model pages for UC315, UC321, UC326 and UC328. The SB range covers SB201 to SB208 and the SA range SA201 to SA210. The catalog size tables above also list the UC 300 sizes without a model page and the UK series, which mount on tapered adapter sleeves with locknuts.

UC204, UC207, UC209 to UC214 and UC315 dimensions on the model pages are from FULI’s catalog. UC205, UC206 and UC208 are cross-checked against FULI’s catalog and published manufacturer datasheets. The SB, SA, UC201 to UC203 and UC321 to UC328 dimensions are cross-checked against several published manufacturer catalogs; send the size you need and we confirm it with the quote.

Insert bearing dimensions and size

Four numbers describe an insert. The bore d is the shaft diameter. The outside diameter D is the diameter of the spherical seat and has to match the housing. The width B is the length of shaft the bearing inner ring covers, including the extension that carries the locking device. The width C is that of the outer race. For SA inserts the catalog also gives B1, the width across the inner ring and collar together.

To read a size from the number, take the last two digits: from 04 upward multiply by 5, so UC205 fits a 25 mm shaft and UC212 a 60 mm shaft. The digit before them is the series: 200 is the light series and 300 the heavier one with a larger outside diameter for the same bore.

Matching the insert to a housing

The insert number is the start of the unit number. A UCP205 pillow block, a UCF205 square flange and a UCFL205 oval flange all use the same UC205 insert; only the prefix changes. To replace a worn insert, order the insert with the same number. To replace the whole unit, compare the housing dimensions as well, because bolt spacing can differ between JIS and ISO versions of the same designation.

See the pillow block bearing and flange bearing pages for housing dimensions, and the pillow block bearing cross reference for brand numbers of the same sizes.

How an insert ball bearing works

An insert is a radial bearing: the balls carry high radial loads and a moderate axial load in both directions. The spherical seat makes the unit self-aligning, so it takes small misalignment from frame welding or shaft deflection. Like other deep groove ball bearings, it runs well at high speeds, with low noise and vibration.

Inserts on this site are sealed bearings. Contact seals with a steel flinger keep contaminants such as dust and water out and the lubricant in. Inserts come with seals or shields: a shield leaves a small gap and suits clean, fast-running machines. Standard UC inserts also have a lubrication hole in the outer race, lined up with the grease fitting on cast iron units, so relubrication is possible without removal. Topping up with the same lubricant extends service life in dirty or wet environmental conditions.

Locking mechanisms

• Set screw lock: UC and SB inserts. Easy to install; suits shafts that run in both directions.
• Eccentric collar: SA inserts. It tightens in the direction of rotation.
• Adapter sleeve: UK inserts, for a firm grip on a plain shaft.
• Concentric collar: used by some other makers, not listed on this site.

Other insert designs

Some ball bearing inserts have a cylindrical outer ring, often with a snap ring, for pressed sheet steel units or rubber mounts. Stainless steel or zinc plated inserts resist corrosion in washdown areas. This site lists the standard chrome steel versions.

Where insert bearings are used

Conveyor systems and conveyor belts, packaging lines, agricultural machinery, textile machines, industrial fans and HVAC systems, and food processing equipment, see grain and food machinery.

Inch bore insert bearings

Our factory also makes inch bore UC inserts. The number after the dash is the bore in sixteenths of an inch: UC205-16 fits a 1 inch shaft and UC208-24 a 1-1/2 inch shaft. The outside diameter and ring widths are the same as the metric insert, so an inch bore insert fits the same housing. The full list with bores in millimetres is on the inch bore pillow block bearing page.

Specifications FULI supplies

Item	FULI specification
Types	UC (set screw), SB (narrow), SA (eccentric collar)
Outside diameter	Spherical, to fit pillow block and flange units
Material	GCr15 chrome bearing steel, rings and rolling elements
Seals	Sealed
Precision	P0 standard
Radial clearance	C0 standard; C3 on request
Supply	Insert only, or fitted as a complete unit

To get a quotation, send the insert number (for example UC205 or UC205-16), the quantity per size and the destination port to sales@fuli-bearings.com or use the request a quote form.