During the maintenance of casters, people usually first inspect the wear on the wheel surface, the condition of the support, and whether the rotation is smooth. However, one area is often overlooked—the fitting part between the wheel shaft and the hub.
After disassembly, some casters reveal that the originally intact wheel shaft has developed noticeable wear marks, with severe cases even forming circular grooves; the hub hole may also gradually enlarge. This phenomenon is commonly referred to as “shaft chewing” on-site.
Strangely, the wheel might still turn, and even the rim remains largely intact.
Then, why is the well-functioning wheel axle being “worn down” bit by bit?
1. During normal rolling, the wheel axle should not serve as the primary friction surface
When the casters roll, the rotational motion should ideally be borne by the designed rotating structure.
For example, wheels with bearings primarily rotate inside the bearing; while casters with bushing structures rely on the interaction between the bushing and the corresponding mating surface.
The wheel axle primarily serves to support and connect.
If during actual operation, significant relative motion occurs at positions where prolonged friction should not be present, the wheel axle may gradually develop abnormal wear.
Therefore, seeing deep grooves on the shaft should not be simply dismissed as “it’s just how it wears over time.”.
2. Abnormal lubrication status is one of the common causes
For rotating structures requiring lubrication, the lubrication condition directly affects the friction of the contact surfaces.
When lubrication is insufficient, the parts that should move relatively smoothly experience increased friction, and the rise in temperature and wear may also intensify accordingly.
However, maintenance should not be simply understood as “the more oil, the better.”.
If there is a high concentration of dust, fibers, or fine particles in the work environment, exposed lubricants may also adsorb contaminants, forming mixed impurities that further affect moving parts.
Therefore, lubrication should be carried out in conjunction with the wheel structure and usage environment, rather than arbitrarily adding excessive oil when rotation becomes unsmooth.
3. Dust and metal debris may become “abrasives.”
In machining, metal manufacturing, woodworking, and certain warehousing environments, there may be a significant amount of fine particles present in the air and on the ground.
If these particles enter the hub, they may become trapped between moving parts.
At this point, the situation is no longer a simple metal contact but may result in an effect similar to “abrasive wear.”.
Especially when harder fine particles enter the mating area, they repeatedly scratch the contact surface as the wheels continue to rotate.
Over time, obvious scratches or even grooves may appear on the surface of the wheel shaft.
4. After the wheel axle wears, the clearance will become increasingly larger
The real trouble with “axis gnawing” lies in its potential to escalate into a worsening cycle.
After internal wear of the wheel axle or hub, the original fit clearance will change.
After the clearance increases, the wheel is more prone to shaking during operation; this shaking alters the contact position, subjecting the wheel axle to more complex forces.
Eventually, there may be noticeable lateral oscillation of the wheels, deterioration in rotational performance, and even abnormal contact between the hubs and brackets.
Therefore, wheel axle wear is not merely an appearance issue.
5. Wheel axle bending may also cause abnormal contact
If the casters have been subjected to significant impact, the axle may bend slightly, which may not be easily noticeable to the naked eye.
But when the wheel rotates, the axis is no longer in an ideal state.
The originally uniform contact may become localized, with certain areas continuously bearing greater friction.
If severe wear is found only in a localized area of the wheel axle after removing the wheel, the straightness of the axle should also be inspected, rather than simply replacing the bushing or bearing.
6. Which on-site performances should be checked in advance?
In fact, before “axis gnawing” reaches a severe stage, the equipment often provides some warning signals.
For example, the wheels are not smooth when idling, with increasing lateral shaking; one wheel of the same device is noticeably harder to turn than the others; periodic friction is felt during operation; and abnormal metal debris is found near the wheel hubs.
When these conditions occur, the wheel axle area can be disassembled and inspected provided that the equipment is securely supported.
The sooner abnormal wear is detected, the easier it is to determine the true cause.
7. When replacing wheels, do not reuse the old wheel axle directly
There is another easily overlooked issue in maintenance:
The wheel is broken; only the wheel will be replaced, and the original axle will be reinstalled.
If the old wheel axle already has obvious grooves, bending, or abnormal wear, the new wheel may still be in an unsatisfactory working condition after installation.
Therefore, when replacing castor components, it is not sufficient to inspect only the “faulty part”; the cooperating wheel shaft, bushing, bearings, and bracket holes should also be examined simultaneously.
Mechanical structures work in interdependent cooperation; a failure in one position often affects adjacent components.
Written later
The “chewing” of casters on shafts usually does not occur suddenly.
It is more like a gradually evolving process: contamination enters, lubrication becomes abnormal, the fit condition changes, and local wear increases before it manifests as visible grooves and shaking.
Therefore, when inspecting casters daily, in addition to checking the wheel surface and bracket, pay more attention to the axle hidden at the hub center.
For more information, please feel free to contact GLOBE Team!
Post time: Sep-12-2026
