An SFU1605 ball screw has a nominal screw diameter of 16 mm and a lead of 5 mm. It is commonly installed with one fixed-side bearing support and one support-side bearing unit, but the correct support model depends on the actual shaft-end machining rather than the SFU1605 model code alone.
BK12/BF12 is a common support-unit combination for an SFU1605 assembly when the screw ends are machined to the corresponding BK12 and BF12 dimensions. EK/EF, FK/FF or customized bearing arrangements may also be used when required by the machine structure.
Fixed-Side and Support-Side Functions
A typical SFU1605 installation uses two different support functions. The fixed side establishes the axial position and rigidity of the screw. The support side helps support the opposite shaft end while avoiding unnecessary axial overconstraint as the screw temperature changes.
| Position | Common Example | Main Function | Installation Concern |
|---|---|---|---|
| Fixed side | BK12, EK or FK series when dimensions match | Provides axial positioning and supports radial load at the machined shaft end | Bearing arrangement, shaft shoulder, locknut and preload must be assembled correctly |
| Support side | BF12, EF or FF series when dimensions match | Supports the opposite end and helps stabilize screw rotation | Must not create an unintended second rigid axial constraint |
A flexible coupling between the motor and screw transmits torque and can accommodate a small amount of permitted assembly error. It should not be used to compensate for a visibly offset or angled ball screw.
A complete ball screw set can include the screw, ball nut, nut housing, coupling, fixed-side support and support-side unit.
SFU1605 Support-Unit Matching Requirements
Confirm the End Machining
The support unit must match the machined shaft ends. Important dimensions include:
- Fixed-side bearing-seat diameter and length
- Shaft shoulder position
- Locknut thread diameter, pitch and thread length
- Spacer or collar dimensions
- Support-side journal diameter and length
- Retaining-ring groove where required
- Coupling-side shaft diameter and engagement length
- Distance between the support-unit mounting faces
The nominal 16 mm screw diameter describes the threaded shaft. The bearing-seat diameter at the machined end is usually smaller and must be checked separately.
Confirm the Support-Unit Size
BK12/BF12 is frequently used for machined SFU1605 assemblies, but it is not universal. If the screw was produced for another support standard or according to a customized drawing, the bearing journals may not fit BK12/BF12.
Before purchasing a replacement support unit, compare the old unit dimensions and the ball screw end drawing rather than relying only on the printed SFU1605 model.
Check Load, Speed and Support Arrangement
The support unit must be suitable for the axial load, screw speed, stroke, duty cycle and required rigidity. A support unit that fits dimensionally may still be unsuitable if its bearing capacity or precision does not meet the machine requirements.
Long SFU1605 screws require additional attention to critical speed, shaft straightness and support rigidity. Increasing motor speed without checking the screw length and support arrangement can cause vibration even when the bearing units are installed correctly.
Pre-Installation Checks
Inspect the Ball Screw and Supports
Check the ball screw shaft, machined journals, threads, nut, seals and support units for impact damage, rust, contamination or deformation. Rotate the bearing units carefully by hand and check for roughness or abnormal looseness.
Do not remove the SFU ball nut from the screw unless the correct transfer sleeve is available. Removing it directly can allow the balls to fall from their circulation paths.
Clean the Mounting Surfaces
Clean the support-unit mounting faces, locating shoulders, nut-housing surface and threaded holes. Remove oil residue, chips, paint buildup and burrs from the machine surfaces without damaging the precision locating areas.
Do not use abrasive paper to resize a bearing seat that does not fit. If the shaft journal or housing dimension is outside tolerance, confirm the drawing and correct the machining rather than manually grinding the surface during assembly.
Check the Machine Mounting Geometry
The fixed-side support, support-side unit and nut housing must share a compatible centerline. The screw axis must also follow the travel direction established by the machine's linear guideways.
Mounting faces should meet the flatness, squareness, height and position requirements of the machine drawing. A support unit should not be pulled into position by tightening bolts across a visible gap.
Prepare the Correct Tools
- Torque wrench suitable for the specified fasteners
- Correct locknut wrench or hook spanner
- Dial indicator and rigid indicator stand
- Clean lint-free cloths
- Manufacturer-approved lubricant if relubrication is required
- Precision shims only where the machine design permits adjustment
- Suitable assembly sleeve or press tools when individual bearings are installed
Avoid applying hammer impact through the ball screw, bearing rolling elements or nut. Installation force should be applied only to the bearing ring being fitted.
SFU1605 Support Bearing Installation Steps
The following sequence describes the general logic of an SFU1605 fixed-and-supported installation. The approved product drawing and support-unit instructions should take priority when they specify a different sequence.
Step 1: Install the Fixed-Side Components
Fit the fixed-side bearing components, spacers and locknut in the specified order. Make sure each component seats against the correct shaft shoulder.
Tighten the bearing locknut according to the specified procedure. Insufficient tightening may leave axial play, while excessive tightening can increase bearing preload, torque and temperature.
Step 2: Position the Fixed-Side Support Unit
Mount the fixed-side housing against its prepared reference surface. Keep the mounting bolts lightly snug if the machine design requires alignment adjustment before final tightening.
Confirm that the locating surface is fully seated and that no chip, burr or paint layer is trapped between the support unit and machine frame.
Step 3: Install the Support-Side Unit
Fit the opposite screw journal into the support-side bearing unit. The support side should stabilize the screw radially without creating an unintended second rigid axial location.
Leave the housing bolts slightly loose if controlled alignment is still required. Do not force the shaft into a support unit that is visibly offset from the fixed-side centerline.
Step 4: Connect the Ball Nut Housing
Attach the SFU1605 nut flange to the matching nut housing and position the housing on the moving table. Initially tighten the table connection only lightly so that the housing can settle into a position compatible with the screw axis.
Support the weight of the screw during installation. The ball nut should not be used to bend or lift the screw shaft into position.
Step 5: Move the Axis Through the Stroke
Rotate the screw slowly by hand or move the axis at the lowest safe speed. Check the fixed-end area, middle of the stroke and support-end area for changing resistance.
The nut should move smoothly without binding. If resistance changes along the stroke, inspect the support-unit centerline, nut-housing height, screw straightness and parallel relationship to the linear guideways.
Step 6: Tighten in a Controlled Sequence
Once the assembly moves smoothly, tighten the fixed-side support, nut housing and support-side unit according to the machine's approved sequence and torque requirements.
Recheck full-stroke movement after each critical component is tightened. A system that moves smoothly while loose but binds after tightening has an alignment or mounting-surface problem.
Step 7: Install the Coupling and Motor
Align the motor shaft and ball screw shaft before tightening the coupling. Confirm that both shaft diameters and insertion depths match the selected coupling.
Do not use a flexible coupling to pull the motor and screw shafts into alignment. Large offset or angular error can overload the coupling, fixed-side bearings and ball nut.
Step 8: Confirm Lubrication
Some complete support units are supplied with sealed or prelubricated bearings. Do not automatically disassemble them or pack the housing completely with additional grease.
If lubrication is required, use the specified grease type and quantity. Excess grease can increase running resistance and temperature, while insufficient lubrication can cause wear and corrosion.
Post-Installation Inspection
After installation, verify the complete assembly before normal-speed operation.
| Inspection Item | Acceptable Condition | Possible Problem if Abnormal |
|---|---|---|
| Full-stroke movement | Smooth and consistent resistance | Misalignment, bent screw or incorrect nut-housing height |
| Axial movement at fixed end | Within the required assembly specification | Loose locknut, bearing play or incorrect fixed-side assembly |
| Noise and vibration | No repeated impact, grinding or cyclic vibration | Bearing damage, coupling error, contamination or runout |
| Motor current or drive torque | Stable through the stroke | Binding, excessive bearing preload or misalignment |
| Bearing temperature | Gradual and stable under controlled running | Over-preload, excess grease, damage or alignment error |
Begin testing at low speed and increase speed gradually. Stop the machine if the assembly develops rapidly increasing temperature, abnormal noise, severe vibration or a sudden torque increase.
For a detailed alignment procedure, read How to Align Ball Screw Support Bearings Correctly .
Common Installation Errors
- Selecting BK12/BF12 from the SFU1605 model name without checking end machining
- Using sandpaper to resize a precision bearing journal
- Hammering the screw shaft or transmitting installation force through the bearing balls
- Installing the support units on dirty or burred mounting surfaces
- Fully tightening the nut housing before checking the complete stroke
- Using the ball screw to pull misaligned linear guideways into position
- Rigidly constraining both ends without considering the intended support arrangement
- Using the coupling to compensate for major motor-to-screw misalignment
- Adding excessive grease to a sealed or prelubricated support unit
- Running at full speed before completing low-speed inspection
Zhejiang DLY Automation Manufacturing Co., Ltd. supplies SFU1605 ball screws, customized shaft-end machining, BK/BF and other support units, couplings and nut housings. Complete sets can be matched according to the end-machining drawing and machine structure.
View the DLY 1605 ball screw page for specifications and available assembly options.
Need an SFU1605 Complete Set?
Send DLY the SFU1605 total length, stroke, end-machining drawing, support-unit type, coupling bore, nut housing and required quantity. We will check component compatibility before quotation.
Email: dlyexport2@dlybearing.com | WhatsApp: +86 166 0578 8856
