SY 40 FM SKF 40 mm - Pillow Block Bearing Unit with Cast Iron Housing

SY 40 FM SKF 40 mm - Pillow Block Bearing Unit with Cast Iron Housing

SY 40 FM SKF is a complete pillow block bearing unit for a 40 mm shaft, consisting of an SKF YET 208 insert bearing mounted in an SY 508 M cast iron housing. The bearing is secured to the shaft by an eccentric locking collar. Its spherical outside surface and corresponding housing seat allow the unit to accommodate initial misalignment between the shaft and housing, making it suitable for conveyors, material handling equipment, industrial machinery and other supported shaft applications.

Technical Specifications - SY 40 FM SKF

Product Type: Pillow block bearing unit
Brand: SKF
Designation: SY 40 FM
Shaft Diameter d: 40 mm
Insert Bearing: YET 208
Housing: SY 508 M
Housing Type: Pillow block / plummer block style
Housing Material: Cast iron
Shaft Locking Method: Eccentric locking collar
Lubrication: Grease lubricated
Relubrication: Yes
Dynamic Load Rating C: 30.7 kN
Static Load Rating C0: 19 kN
Fatigue Load Limit Pu: 0.8 kN
Limiting Speed: 4,800 r/min
Weight: approximately 1.85 kg

Dimensions of the SKF SY 40 FM

The principal mounting dimensions are:

d: 40 mm
A: 48 mm
A1: 30 mm
A5: 26 mm
H: 99 mm
H1: 49.2 mm
H2: 19 mm
J: 135.5 mm
J min.: 125 mm
J max.: 146 mm
L: 175 mm
N: 24.5 mm
N1: 14 mm
B1: 43.2 mm
s1: 32.7 mm

Unlike a conventional rolling bearing, a complete pillow block unit should not be identified only by three dimensions. The 40 mm shaft diameter, mounting hole spacing, shaft center height and housing dimensions are important when selecting a replacement.

YET 208 Insert Bearing

The SY 40 FM bearing unit incorporates an SKF YET 208 insert bearing.

This bearing has a 40 mm bore and an extended inner ring. It is designed to be secured to the shaft using an eccentric locking collar.

The spherical outside surface of the bearing fits into the corresponding spherical seat of the housing.

This arrangement enables the assembled unit to accommodate a degree of initial alignment error between the shaft and supporting structure.

SY 508 M Cast Iron Housing

The bearing is installed in an SY 508 M housing.

The cast iron housing provides a rigid support structure and a base that can be bolted directly to the machine frame.

Its principal dimensions include:

Overall Length L: 175 mm
Overall Height H: 99 mm
Shaft Center Height H1: 49.2 mm
Housing Width A: 48 mm

The elongated mounting holes provide adjustment capability during installation.

Eccentric Locking Collar

An important feature of the SKF SY 40 FM is its eccentric shaft locking system.

The eccentric collar engages with the corresponding eccentric extension of the bearing inner ring. Rotating the collar in the appropriate direction creates the locking action, after which the collar is secured using its locking screw.

This system provides a practical method of locating the bearing on a straight 40 mm shaft.

Eccentric locking collar arrangements are particularly suitable for applications where the shaft normally rotates predominantly in one direction.

Initial Misalignment Compensation

The insert bearing has a spherical outside surface that works together with the spherical seating surface inside the housing.

This geometry allows the unit to compensate for initial static misalignment between the shaft and housing.

This feature can simplify installation where minor alignment differences occur between bearing supports.

However, the self-aligning capability should not be interpreted as allowing continuous shaft deflection or dynamic misalignment during operation. Correct shaft alignment and structural rigidity remain important.

Load Ratings

The principal load ratings for the unit are:

Basic Dynamic Load Rating C: 30.7 kN
Basic Static Load Rating C0: 19 kN
Fatigue Load Limit Pu: 0.8 kN

These values are important when evaluating the bearing unit for a particular machine.

Actual bearing service life depends on the applied load, speed, lubrication, contamination, operating temperature, alignment and duty cycle.

Relubrication and Maintenance

The SY 40 FM SKF is grease lubricated and designed to permit relubrication.

Relubrication can be particularly useful in equipment operating for extended periods or under conditions involving contamination, moisture or elevated operating temperatures.

The appropriate relubrication interval depends on:

• rotational speed
• operating temperature
• contamination level
• moisture
• load
• operating hours
• environmental conditions

Excessive lubrication should also be avoided, as overfilling can increase friction and operating temperature.

Industrial Applications

The SKF SY 40 FM 40 mm pillow block bearing unit can be used in appropriately designed:

• conveyor systems
• material handling equipment
• industrial machinery
• production lines
• packaging machinery
• agricultural machinery
• fans
• auxiliary drives
• processing equipment
• supported shaft systems

The complete bearing arrangement should always be evaluated according to load, speed, shaft design and environmental conditions.

SY 40 FM for Conveyor Systems

Pillow block bearing units are widely used for supporting rotating shafts in conveyor and material handling systems.

The 40 mm bore allows the SY 40 FM to be mounted on an appropriately dimensioned shaft, while the cast iron housing provides a stable connection to the supporting machine structure.

The eccentric locking collar simplifies shaft fixation, and the relubrication capability supports maintenance in continuously operating industrial equipment.

Complete Bearing Unit vs Housing

An important distinction should be made between the complete SY 40 FM unit and its individual components.

SY 40 FM: complete bearing unit
SY 508 M: cast iron housing
YET 208: insert bearing

Therefore, SY 40 FM is not simply a bearing housing.

When ordering a replacement, this distinction is important because purchasing only the housing does not provide the complete bearing unit.

How to Select an SY 40 FM Replacement

Before selecting a replacement bearing unit, verify:

Designation: SY 40 FM
Brand: SKF
Shaft Diameter: 40 mm
Insert Bearing: YET 208
Housing: SY 508 M
Housing Material: Cast iron
Locking System: Eccentric locking collar
Mounting Dimensions: Compatible with the machine
Shaft Center Height: Compatible with the existing arrangement
Load Capacity: Suitable for the application
Speed: Suitable for operating conditions

A 40 mm bore alone is not sufficient to identify a fully interchangeable bearing unit.

Operational Advantages

Complete bearing unit: combines the YET 208 insert bearing with the SY 508 M housing.

40 mm bore: designed for installation on a nominal 40 mm shaft.

Cast iron housing: provides rigid support for industrial shaft arrangements.

Eccentric locking collar: provides practical fixation of the inner ring to the shaft.

Relubrication capability: supports maintenance in long-term industrial operation.

Initial misalignment accommodation: spherical bearing seating helps compensate for initial alignment errors.

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FAQ - SY 40 FM SKF

What is the SKF SY 40 FM?
The SY 40 FM is a complete pillow block bearing unit for a 40 mm shaft, consisting of an insert bearing mounted in a cast iron housing.

Which bearing is used in the SY 40 FM?
The complete unit uses an SKF YET 208 insert bearing.

Which housing is used in the SY 40 FM?
The bearing is installed in an SY 508 M cast iron housing.

What shaft diameter is the SY 40 FM designed for?
It is designed for a nominal 40 mm shaft diameter.

How is the bearing secured to the shaft?
The YET 208 insert bearing uses an eccentric locking collar to secure the inner ring to the shaft.

What is the weight of the SKF SY 40 FM?
The complete bearing unit weighs approximately 1.85 kg.

What is the dynamic load rating of SY 40 FM?
The basic dynamic load rating C is approximately 30.7 kN.

Can the SY 40 FM be relubricated?
Yes. The bearing unit is designed to permit relubrication during service.

Frequently Asked Questions by Engineers

Is SY 40 FM a complete bearing unit or only a housing?
It is a complete bearing unit. The SY 508 M is the housing, while YET 208 is the insert bearing.

Can SY 40 FM compensate for shaft misalignment?
Its spherical bearing-to-housing interface can accommodate a degree of initial static misalignment. It is not intended to compensate for continuous dynamic shaft deflection.

Is a 40 mm bore enough to select an equivalent unit?
No. Housing dimensions, mounting hole spacing, shaft center height, locking method, bearing design and load ratings should also be checked.

What is the shaft center height of the SY 40 FM?
The H1 dimension, representing the shaft center height, is approximately 49.2 mm.

When is eccentric locking useful?
Eccentric collar locking provides a straightforward method of securing an insert bearing to a straight shaft and is commonly used where the direction of rotation is predominantly constant.