My new sintered bushing seized almost immediately after fitting - why?

The most common cause is insufficient running clearance, often because press-fitting into an interference housing closed the bore. A sintered bushing's bore shrinks when pressed in, so the free-state bore is not the running bore. Design in the close-in or ream to final size after fitting, and set clearance for the hot operating condition, not the bench temperature.

Can I just add oil to a squealing self-lubricating bushing to quieten it?

A surface oiling may quieten it briefly, but squeal means the internal film mechanism is starved or the running conditions are wrong. Diagnose the cause - depleted charge, wrong oil grade, too-tight clearance or an unsuitable shaft finish - and fix that. If the internal charge is genuinely depleted, proper re-impregnation restores the reservoir far better than surface oil.

How can I tell wear from seizure on a removed bushing?

Wear shows as gradual, usually fairly even bore enlargement with a polished or glazed surface and increasing clearance. Seizure shows as scoring, torn zones and material smeared between shaft and bore, often with the bore having closed or picked up rather than opened. Even wear points to lubrication or contamination; localised scoring at one end points to clearance, alignment or overheating.

Does bore wear on one side only mean a defective bushing?

Almost never. One-sided or edge-concentrated wear points to misalignment, shaft deflection or edge-loading that concentrates the load and collapses the film on that side first. Check shaft alignment and support, consider a longer bushing to spread the load, and confirm the housing is square before assuming the part is at fault.

Troubleshooting Bushing Wear, Noise & Seizure

Oil-impregnated sintered bushings are designed to run untouched for their whole life, so when one wears rapidly, squeals or seizes, it is almost always signalling a design, installation or environmental problem rather than a defective part. The porous bronze or iron matrix and its internal oil charge fail in recognisable patterns, and each pattern points to a cause. Reading the failure mode correctly is the fastest route to a durable fix.

Start by reading the bushing

Before changing anything, examine the removed bushing and the shaft. A self-lubricating bearing tells its own story: the colour, finish and geometry of the worn bore identify how it failed. Note whether wear is even around the bore or concentrated on one side, whether the surface is polished, glazed, scored or discoloured, and whether the shaft shows matching marks. Compare the worn bore against nominal to see if the clearance opened up gradually (wear) or the bore closed and picked up (seizure). These observations separate the main failure families below.

Excessive or rapid wear

Uniform bore enlargement over a short time usually means the oil film is not being maintained. Common root causes:

Wrong oil for the duty. A high-speed application charged with too heavy an oil, or a slow heavily loaded one charged with too light an oil, spends too long in boundary contact. Re-specify from the range - lighter PE1116/PE1152 for speed, boundary-supporting METADOP for slow heavy load.
Closed surface porosity. If the bushing was pressed with open jaws or an oversized interference, the bore surface can be smeared shut so oil cannot bleed. The fix is correct closed-arbor tooling and the specified housing fit.
Abrasive contamination. Hard fines embed in the porous surface and lap the shaft. Add sealing or a wiper, and check the shaft hardness and finish.
Overload. Sustained load beyond the film's capacity thins it to metal contact. Increase bearing area, reduce load, or move to a higher-capacity matrix such as FP20 for slow duty.

Noise: squeal, chatter and stick-slip

A previously quiet bushing that starts to squeal or chatter is almost always short of film. Squeal is the audible signature of intermittent boundary contact and stick-slip - static friction repeatedly overcoming kinetic friction and releasing. Likely causes and remedies:

Depleted or displaced oil charge. Solvent cleaning, prolonged storage in the dry, or overheating that ages the oil can starve the interface. Confirm the correct oil family and, if depleted, re-impregnate rather than surface-oiling.
Too-smooth or too-hard counterface interaction. An incompatible shaft finish can prevent stable film formation. Verify shaft roughness and hardness against the recommendation for the class.
Insufficient clearance. Too tight a running fit leaves no room for the film and for thermal growth, forcing boundary running. Confirm the after-fitting bore against the required clearance, remembering that press-fitting closes the bore slightly.
Low-speed oscillation. Duties that never build a hydrodynamic film benefit from a boundary-active oil such as METADOP to lower the static-to-kinetic friction gap that drives stick-slip.

Seizure and pick-up

Seizure - the shaft and bore adhering, scoring or locking - is the most serious mode and usually stems from the film collapsing completely and metal cold-welding. Diagnose by the trail of evidence:

Insufficient running clearance or thermal lock. If clearance was too small, frictional heat expands the shaft into the bore until it binds. This is the classic seizure cause. Set clearance for the operating temperature, not the bench.
Press-fit closing the bore. A sintered bushing's bore shrinks when pressed into an interference housing. Design for this close-in or ream to final size after fitting; do not assume the free bore is the running bore.
Loss of lubrication under load. Combined overload and starvation drives adhesive transfer. Look for bronze or iron smeared onto the shaft and matching torn zones in the bore.
Overheating past the oil's limit. Sintered bronze bushings of this type typically operate to around 100 C continuous with mineral charges; beyond the oil's thermal band the film degrades and the interface picks up. If the duty runs hot or continuous, move to an oxidation-stable oil such as TURBO T100 and check the heat path.
Misalignment or edge-loading. A cocked or deflected shaft concentrates load on a bore edge, collapsing the film there first. Seizure that starts at one end of the bore points to alignment. Correct alignment, add bearing length, or consider a self-aligning arrangement.

A short diagnostic routine

Work the problem in order: (1) confirm the after-fitting running clearance against requirement, since too-tight fits cause a large share of noise and seizure; (2) verify the matrix and oil suit the real load, speed and temperature; (3) inspect the shaft finish, hardness and alignment; (4) check for contamination ingress; (5) confirm the bushing was pressed with correct tooling so the surface porosity is open. Most field failures resolve to one of these five, and each has a concrete fix within the Bushingo range - a different oil, a different matrix grade, a corrected fit or a protected environment - rather than simply fitting the same part again.