A replacement Screw Conveyor End Bearing may line up with the conveyor end plate and match every bolt hole, yet its splined shaft may still refuse to enter the mating connection.
On a splined end-bearing assembly, this means the visible mounting dimensions and the internal shaft connection are not confirming the same fit. Tightening the flange bolts will not answer which interface is wrong—and may damage the evidence needed to find out.
Whether the spline will not start, stops at a repeatable depth, or enters only when the screw shaft is lifted usually provides a better clue than the flange pattern alone.
This article concerns end-bearing assemblies with an external splined shaft engaging a matching bush or sleeve inside the screw shaft. Other end-bearing arrangements may require a different inspection method.
Why a Matching Flange Does Not Confirm the Spline
The flange and spline belong to the same assembly, but they confirm different parts of the installation.
The flange determines whether the bearing housing can be positioned on the conveyor end. Its fit depends on features such as:
- Bolt-hole pattern
- Flange outside diameter
- Locating diameter
- Mounting-face position
The spline determines whether the end-bearing shaft can engage the existing screw shaft connection. Compatibility may depend on:
- Tooth count
- Tooth form
- Major diameter
- Effective engagement length
- Shaft shoulder position
- Distance between the spline and flange face
A replacement can therefore match the visible mounting flange while differing at the internal connection.
The nominal Screw Conveyor diameter can help narrow the possible model range, but it does not confirm the complete end-bearing assembly. The spline and axial dimensions still need to agree with the existing configuration.
Read the Problem from Where the Spline Stops
Before measuring every visible dimension, observe exactly how the fitting attempt fails.
| Observed fitting behaviour | Main areas to check |
|---|---|
| The spline will not start in the mating bush | Tooth form, tooth count, diameter, buildup, burrs or entrance damage |
| It enters smoothly and stops at the same depth | Internal obstruction, local tooth damage, insufficient internal depth or incorrect spline length |
| It appears engaged but the flange remains away from the mounting face | Shaft shoulder position, flange-to-spline dimensions or another axial interference |
| It enters only after the screw shaft is lifted or moved sideways | Installed shaft position, unsupported shaft weight or disagreement between the shaft and flange centres |
These observations do not prove the cause on their own. They indicate where the inspection should begin.
Before repeating the test, isolate and empty the conveyor, prevent unexpected movement and support the screw shaft securely. Present the spline without hammering it or applying force through the mounting bolts.
Do Not Use the Flange Bolts to Pull the Connection Together
When the spline stops, tightening the flange bolts may draw the housing toward the mounting face. That does not mean the internal connection is correct.
The bolts can apply enough axial force to:
- Press incompatible tooth edges together
- Push the spline against the bottom of the mating bush
- Compress a seal or spacer incorrectly
- Pull the screw shaft away from its natural position
- Damage the entrance of the internal teeth
The flange may eventually appear flush while the spline remains only partly engaged or contacts heavily on one side.
Forced installation also removes useful evidence. Once tooth tips have been scraped, rolled or crushed, it becomes harder to determine whether the original cause was an incorrect spline, a damaged mating bush or an axial-dimension mismatch.
If the parts do not come together under controlled alignment and light manual fitting force, stop and identify the interference before tightening the bolts.
When the Spline Will Not Start
A spline that will not enter at all usually points to interference near the entrance or a basic mismatch between the tooth forms.
Clean the connection before comparing specifications. Cement residue, hardened powder, corrosion, paint or compacted grease can fill the internal tooth spaces and make a compatible replacement appear oversized.
Inspect the entrance of the mating bush and the first section of the replacement spline for:
- Raised burrs
- Flattened tooth tips
- Impact marks
- Corrosion around the opening
- Weld spatter
- Paint on the spline
- Hardened material between the internal teeth
- Damage to the lead-in edge
Gently rotating the shaft without applying axial force can help reveal whether one damaged tooth or local contact point changes the fitting behaviour. The purpose is not to find a special installation angle. A correctly matching spline should not need to be forced through one particular rotational position.
If cleaning does not change the fit, compare the old and new splines from both the side and the end.
A similar outside diameter is not enough. Two splines may look close in size while differing in tooth count, tooth thickness, root shape or another profile feature.
Measurements taken on site are useful for an initial comparison, but a caliper cannot reliably confirm every spline detail—especially when the removed part is already worn. A verified model designation, drawing or undamaged sample is more reliable when available.
Partial Entry and a Remaining Flange Gap Mean Different Things
A spline that enters part of the way has already confirmed that the first section of the connection is at least close enough to begin engaging.
Use a removable marker to record the depth where it stops. After withdrawing the end bearing, compare that point with visible contact marks and the available depth inside the mating bush.
A repeatable stopping point may be caused by:
- Material packed deeper inside the bush
- A locally deformed group of internal teeth
- Corrosion beyond the entrance
- Distortion near a previously welded area
- A replacement spline extending farther than the available internal depth
A different condition exists when the spline appears to enter fully but the bearing flange still cannot reach the mounting face.
In that case, the interference may not be at the spline teeth. The shaft shoulder, housing, seal arrangement or another axial feature may be reaching its mating position too early.
Compare dimensions from the flange mounting face rather than measuring only the exposed spline:
- Flange face to the beginning of the spline
- Flange face to the end of the spline
- Flange face to the shaft shoulder
- Usable depth inside the mating bush
A longer spline is not automatically better. It must fit within the confirmed internal depth while still allowing the housing to reach its intended mounting position.
When the Shaft Must Be Lifted Before the Spline Enters
Sometimes the spline appears compatible but will only begin entering after the screw shaft is lifted, lowered or pushed sideways.
This suggests that the two spline components may match, while their centre lines do not naturally meet in the installed position.
Possible reasons include:
- The unsupported screw shaft has dropped under its own weight
- The end plate is not centred on the shaft
- The bearing flange is being presented at a slight angle
- A nearby support is holding the shaft away from the opening
- The casing or mounting surface moved during an earlier repair
Support the shaft in a neutral position and present the end bearing without using the housing to reposition the shaft. The spline should begin engaging before the mounting bolts are used for final fastening.
Where the conveyor construction permits a safe separate check, the spline and mating bush can also be held coaxially away from the final mounting face. If they engage in that position but bind at the conveyor end, examine the installed shaft and flange positions before rejecting the replacement part.
Problems that continue after the bearing has been installed—such as repeated heating, off-centre running or Screw Flight contact—require a wider shaft-line inspection and should not be diagnosed from the spline fit alone.
Why the Old End Bearing May Fit When the New One Does Not
An old end bearing that still enters the screw shaft does not automatically prove that the replacement is incorrect.
The old external spline and the mating bush may have worn together over time.
The external teeth may have become thinner, allowing the old shaft to pass through an entrance that now contains:
- Raised metal
- Local deformation
- Corrosion
- Uneven internal wear
- A partly damaged tooth
An unworn replacement can then stop at the damaged area even though the old component still passes through it.
The fitting behaviour may differ according to the condition of the mating bush:
- Uniform wear may let the new spline enter but leave excessive movement.
- Raised metal near the entrance may prevent it from starting.
- One damaged internal tooth may stop it at a repeatable angle or depth.
- Deep corrosion or compacted powder may make the fit progressively tighter.
- Distortion near a repaired or welded area may reduce the available internal space.
Inspect the mating bush or splined sleeve before removing material from the new end bearing.
Grinding the new teeth to reproduce the clearance of a worn component may make installation easier while creating an uneven or excessively loose connection. When the mating bush is damaged, the repair may need to include the bush or shaft-end section instead of replacing only the end bearing.
The correct repair scope depends on the confirmed internal construction and condition of the conveyor.
What to Confirm Before Reordering the End Bearing
A heavily worn removed part should be treated as evidence, not as a perfect dimensional master.
Before ordering another replacement, confirm the features that explain both the flange fit and the spline engagement:
- Flange locating diameter
- Bolt-hole quantity and pattern
- Spline tooth count
- Maximum spline diameter
- Spline designation or standard, when known
- Effective spline length
- Distance from the flange face to the shaft shoulder
- Available depth and condition of the mating bush
Take dimensions from the least damaged areas available. Do not use visibly thinned or flattened tooth sections as the assumed original specification.
Useful photographs include:
- The old and new splines placed side by side
- A direct end view showing the tooth pattern
- A side view showing the flange, spline and shaft shoulder
- The complete mounting flange
- The entrance and visible interior of the mating bush
- Any polished, burred or deformed tooth area
A photograph showing only the bearing housing and flange cannot confirm whether the internal shaft connection will engage.
When no drawing or readable part number is available, dimensions and clear end-view photographs of both mating components are more useful than the conveyor diameter alone.
Questions Customers Ask About End-Bearing Spline Fit
screw conveyor end bearing
The conveyor diameter usually identifies only part of the required configuration.
Different assemblies used on a similar tube size may still have different flange layouts, spline profiles, engagement lengths or shaft-shoulder positions. The complete connection must be confirmed rather than relying on diameter alone.
Not necessarily.
The old spline may be worn, previously modified or able to pass through a damaged mating bush because its teeth have become thinner. Compare the replacement with confirmed dimensions and inspect the internal connection before rejecting it.
Avoid treating the most heavily worn tooth area as the original size.
Measure a less-worn section where possible, inspect the mating bush and use the original model, drawing or a verified sample when available. End and side photographs can also help distinguish the intended profile from wear damage.
It may be, but the gap can also result from an axial-dimension difference.
Check the internal depth, shaft-shoulder position and distances measured from the flange face. The spline can enter the bush while another part of the shaft reaches its stopping point too early.
Do not alter the spline until the interference has been identified.
A confirmed local burr may be dressed under a controlled repair procedure, but grinding should not be used to make an unknown spline specification fit. Removing material without confirming the cause can create excessive clearance or uneven tooth contact.
Photographs can support identification, but they should be accompanied by measurements.
Provide direct end and side views of the spline, the complete flange, the old component and the mating bush. Tooth count, spline diameter, effective length and dimensions measured from the flange face are particularly useful.
