Running clearance on shaft
- Shaft spins or slides inside the bushing ID
- ID grows with heat and moisture in nylon
- Call fit after molding stabilization if critical
Molded part guide: bushings
Injection Molded Bushings
A molded bushing is a short sleeve whose inside runs on a shaft and whose outside stays put in a housing. Success is boring in the good way: round bore, stable OD, and a resin that survives sliding without galling.
Plain bearing
Sliding, not rolling
Molded bushings guide shafts, isolate metal-on-metal, and quiet hinge pins. They are not ball bearings. Load, speed, and temperature stay lower than a rolling element, but mold cost and part cost are lower too.
Acetal is the default for dry sliding against steel. Nylon adds toughness. PTFE-modified grades reduce friction when grease is not allowed. Glass fill adds stiffness but roughens the bore against soft shafts.
The bushing either presses into a reamed housing bore or molds in place as a insert. Press-fit retention depends on OD interference and whether the housing is plastic or metal.
Fit
Clearance bore for sliding or interference for press fit
Press fit OD in housing
- Bushing OD elastically displaces housing material
- Knurl or barbs on OD reduce push-out
- Housing wall must be thick enough to resist hoop stress
Tooling
Concentricity from gate and core support
- Gate into the flange end, not into the bore landing
- Long cores need support to prevent bore taper
- Thin sleeves warp if wall is not balanced around the bore
- Call concentricity between bore and OD when the assembly needs it
Drawing
Bushing quote inputs
Shaft diameter, material, and surface finish
Housing bore and whether the bushing is pressed or molded in
Load, speed, and temperature in service
Lubrication allowed or dry only
Flange, snap ring groove, or knurl on OD
Concentricity or runout callouts if any
Keep reading
Related guides
Acetal (POM)
Default bushing resin.
Acetal (POM)Acetal vs nylon wear
Pairing to shaft and housing.
Acetal vs nylon wearRollers
Rolling cousin to sliding bushings.
RollersSpacers
Distance without a sliding bore.
SpacersHinges
Pin in a molded knuckle.
HingesInsert molding
Bushing molded into housing.
Insert moldingStandard tolerances
What molded bores hold.
Standard tolerancesGears
Bore fit on gear hubs.
GearsMolded parts hub
Every part-type guide.
Molded parts hubFAQ
Questions about molded bushings
Can a molded bushing replace a bronze sleeve?
Often on light loads and moderate speed. Heavy load or high temperature may still need metal or a rolling bearing. Send load and speed for review.
Do you ream the bore after molding?
Secondary machining is possible when drawings require it. Many bushings run as-molded with fit verified on samples.
Why does the shaft seize in nylon bushings?
Moisture swelling, heat, or grit in the bore are common. Check resin grade, clearance, and whether the mate shaft is harder than the bushing.
Can the bushing mold as part of the housing?
Yes as an integral bore, but replacement and wear are harder. Separate bushings are common when service matters.
Next step
Quote the bushing with shaft and housing fits
Upload CAD with ID, OD, and load case. DFM feedback covers core support, concentricity, and resin pairing.