Plain bushings

For igus JSM-2023-20, the installed bore in the specified H7 housing is 20.040–20.124 mm. With the listed 19.948–20.000 mm shaft, diametral clearance spans 0.040–0.176 mm, or 0.020–0.088 mm radially. This uses catalog limits after press fitting. Verify the actual housing, counterface and operating load and temperature. igus J catalog, p. 4.12.

Sliding support and load path

A sleeve supports radial load through sliding contact. Flanged designs add an axial face. Rotation, oscillation and translation impose different conditions. GGB, Bearings.

Load passes from the shaft through the sliding liner and its backing to the housing. Check flange thrust and housing strength separately.

Construction and lubrication are separate choices

GGB describes these as different bearing families, with dry-running and externally lubricated variants. “Self-lubricating” therefore describes a material/construction capability, not proof that every bearing can run without oil or grease. GGB construction overview.

Lubrication also changes the contact mechanism. In a hydrodynamic journal bearing, relative motion and clearance generate a load-supporting lubricant wedge that separates the surfaces. During starting and stopping, mixed friction can occur before full film separation develops. A hydrostatic bearing instead uses externally pressurised lubricant. These fluid-film systems have geometry, viscosity and supply requirements; adding grease to a dry-running sleeve does not by itself establish hydrodynamic operation. KSB, Plain bearing, centrifugal-pump context.

Projected pressure, velocity and p-v

For a cylindrical sleeve under radial force F, the conventional projected area is A = d × B, where d is shaft diameter and B is bearing length. The nominal specific pressure is:

p = F / (d B)

With N and mm, p is N/mm², equivalent to MPa. It is an average over the projected rectangle, not the curved area πdB or the maximum local contact stress. igus defines load using this projected-area convention. Its maximum recommended pressure is a static material parameter at +20°C, not a general dynamic load rating. igus, Surface pressure and load.

Relative sliding speed matters, rather than either component's absolute speed. For steady rotation with shaft diameter d in mm and relative speed n in revolutions per minute, circumference per revolution gives the derived relationship v = πdn/60000 in m/s. Oscillating and reciprocating motion additionally have reversals and a speed history; a rotation formula applied to cycle frequency alone would omit stroke or angle. igus, Surface speed.

The product p × v, in MPa·m/s, is a thermal screening quantity. Permissible p-v depends on heat removal through the bearing, shaft and housing, ambient temperature and operating time. Intermittent operation can permit cooling between movements; duty cycle and dwell are consequently different from continuous operation. igus also describes lubrication as influencing frictional heat and permissible p-v. A dry-running limit and a lubricated limit are different conditions. igus, p-v value and lubrication.

Engineering synthesis: for a simple sliding-friction model, dissipated power is approximately μFv. Dividing by projected area gives μpv, so p-v alone does not include friction coefficient or actual thermal resistance. Being below one p-v number cannot independently establish acceptable temperature, deformation, wear or life. Pressure, speed and temperature maxima do not form a box in which every combination is permissible.

Counterface, wear and clearance

Friction coefficient is a property of the operating pair and conditions, not a universal constant for “plastic” or “bronze”. igus describes dependence on pressure, speed, temperature and shaft finish. Excessively rough shafts promote abrasion; overly smooth pairings can increase adhesion and stick-slip. Minimum roughness is therefore not automatically the best finish. igus, Coefficients of friction.

The shaft also wears. Its material, hardness, coating and roughness influence running-in and subsequent behaviour. igus's shaft comparisons specify test pressure, speed and finish; results for one counterface are not measurements for another shaft. Surface hardness alone does not describe the complete sliding pair. igus, Shaft materials.

Running clearance is the installed bearing bore minus shaft diameter; radial clearance is half that diametral difference for concentric circular geometry. Housing interference retains a press-fit sleeve, while running clearance permits relative motion. They are different interfaces. For its standard polymer bearings, igus describes the bore forming after installation in an H7 housing and identifies housing tolerance, shaft tolerance and environmental expansion as relevant. A free-standing sleeve bore is not its final installed bore. These are igus-specific installation relationships, not a universal H7 fit prescription. igus, Installation and tolerances.

Engineering synthesis: shaft bending, misalignment, ovality and a compliant housing can concentrate contact near an edge even when average projected pressure is modest. Thermal expansion, moisture uptake and wear can change clearance. Neither a nominal-size match nor low calculated p-v establishes freedom from seizure, excessive play or edge wear.

Bounded example: igus JSM-2023-20

The manufacturer's iglide J sleeve catalog, PDF page 12, printed page 4.12, lists JSM-2023-20. This is a bounded catalog example, with no edition date visible on the relied-on page. igus J catalog, p. 4.12.

Derived clearance: using that row's bounds, minimum diametral clearance is 20.040 − 20.000 = 0.040 mm; maximum is 20.124 − 19.948 = 0.176 mm. Corresponding radial clearances are 0.020–0.088 mm. These are tolerance-stack calculations for the listed installation, not measured clearances or universal targets. Nominal wall thickness is (23.0 − 20.0)/2 = 1.5 mm.

The manufacturer's related iglidur J Product Data Sheet, QS F-2-0105-C, printed creation 19 November 2013, change 4 December 2019, page 1 of 1, specifies 35 MPa maximum permissible surface pressure at 20°C and 90°C highest long-term service temperature. Its 120°C short-term service and 140°C short-term ambient entries carry the conditions without additional load and no movement; the temperature entries also warn that relaxation is possible. These are material-data limits, not a measured JSM-2023-20 operating envelope. Manufacturer J sheet.

The separate UK J material page describes dry operation and lists maximum permanent speeds of 1.5 m/s rotating, 1.1 m/s oscillating and 8 m/s linear, achievable only at low pressure loads. At 90°C it describes permissible pressure as approximately 20 MPa. This approximation is not an exact dynamic rating. The page expressly separates mechanical pressure capacity from tribological performance; its independent maximum-speed and pressure entries are not simultaneous capabilities.

Illustrative arithmetic: for the nominal 20 mm shaft and 20 mm sleeve length, assume a uniformly represented 400 N radial load and 60 rpm steady relative rotation. Then A = 400 mm², p = 1 MPa, v ≈ 0.06283 m/s, and pv ≈ 0.06283 MPa·m/s. This computes inputs to an application assessment; it does not establish a temperature, lubricant requirement, allowable duty or service life. No measured wear or lot-specific performance is inferred from those nominal dimensions.

Evidence and applicability limits

Sources were accessed 2026-10-31 PDT. The J catalog is a 16-page PDF; only its relied-on page 12 was visually read. Its PDF creation/modification metadata is dated 30 June 2011, which is not treated as a printed edition. The one-page material sheet was visually read in full: its printed 2013/2019 dates differ from PDF metadata dated 4 August 2021. The URL filename and metadata do not establish a later technical revision. The catalog's US “iglide” naming and the UK “iglidur” material references remain separately identified; this comparison is not current procurement or lot certification.

The JSM-2023-20 example is bounded by the cited catalog row and the separately identified J material references; this source set does not establish a current model-specific product-page specification. GGB coverage is limited to the cited primary-source text.

No full ISO, DIN or ASTM standard was read. The sources do not establish a customer's exact formulation, lubrication state, counterface, alignment, operating temperature, load spectrum or required life. Numerical examples here are catalog facts or explicitly derived arithmetic. Universal friction, clearance, fit, p-v and life limits are not established.