SYZ ENGINEERING PRELIMINARY DESIGN TOOL · REFERENCE-BASED ESTIMATE

Spherical Bearing PV & Oscillation Duty Calculator

Estimate bearing pressure, sliding velocity and PV value for an oscillating (non-rotating) spherical bearing or rod end, and compare against commonly published PTFE-liner PV bands.

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BEARING WEAR RATE · PV (PRESSURE × VELOCITY) METHOD

Spherical Bearing PV & Oscillation Duty Estimator

Estimates bearing pressure, sliding velocity and PV value for an oscillating (non-rotating) spherical bearing or rod end, and compares against commonly published PTFE-liner PV bands.

Radial Load [lbf]

Bore Diameter [Inches]

Bearing / Ball Width [Inches]

Projected bearing area = bore × width.

Oscillation Frequency [Cycles / Minute]

One cycle = one full back-and-forth swing.

Swing Angle [Degrees, total arc]

Calculated PV Value

9,973

P = 15,238 psi · V = 0.654 ft/min · units: psi·ft/min

⚠ Heavy duty — approaching commonly published PTFE composite liner limits. Verify against your bearing supplier’s datasheet.

Engineering Model (SYZ-defined oscillation convention)

Calculation Method P = Load / (Bore × Width) · V = π × Bore × Cycles/min × (Swing° / 180) / 12 · PV = P × V

Standard Reference PV as a bearing wear-rate design parameter is widely used across plain-bearing engineering (e.g. Igus, GGB, Kaydon catalogs), but there is no single universal formula for oscillating-duty velocity — manufacturers define it differently. The formula above is SYZ’s own explicit definition (arc length swept per cycle × cycle rate); always cross-check against your specific bearing supplier’s PV methodology before final selection.

SYZ Guideline PV Bands <3,000 psi·fpm: light duty · 3,000–10,000: moderate duty (typical street/light off-road) · 10,000–15,000: heavy duty, approaching commonly published PTFE-liner limits · >15,000: very heavy, likely exceeds standard PTFE-liner ratings.

Assumptions & Limitations

PV limit bands are SYZ’s own guideline, informed by commonly published PTFE composite liner ratings — not a single certified number, and vary by liner material, temperature and lubrication.
Assumes uniform bearing pressure across the projected area — real contact pressure is not uniform (Hertzian contact effects near the edges).
Metal-on-metal or greased bearings can tolerate substantially different PV limits than PTFE-lined bearings — this tool’s reference bands assume a PTFE-composite liner.
Does not account for temperature rise, which strongly affects real bearing life at high PV.

STATIC REFERENCE DATA

Reference: PV Value by Bore Size (4,000 lbf, 30 cpm, 20° swing)

Precomputed values from the exact formula used above — useful as a quick lookup without re-entering inputs.

Bore Diameter	Width (typical ratio)	Pressure (P)	Velocity (V)	PV Value
1/2″	0.291″	27,444 psi	0.436 ft/min	11,975 psi·fpm
5/8″	0.364″	17,564 psi	0.545 ft/min	9,580 psi·fpm
3/4″ (calculator default bore)	0.437″	12,197 psi	0.654 ft/min	7,983 psi·fpm
1″	0.583″	6,861 psi	0.873 ft/min	5,987 psi·fpm

Width scaled proportionally to bore (≈0.583× bore) as a typical rod-end ball-width ratio for illustration — enter your actual bearing width in the calculator above for a precise result.

WORKED EXAMPLE

Checking a 3/4″ Rod End for Steady Oscillating Duty

A 3/4″ bore, 7/16″-wide rod end carries a 5,000 lbf radial load in a linkage that oscillates 30 times per minute through a 20° swing. Is this within a reasonable PV duty range for a PTFE-lined bearing?

Bearing pressure P = 5,000 / (0.75 × 0.4375) ≈ 15,238 psi.
Sliding velocity V = π × 0.75 × 30 × (20/180) / 12 ≈ 0.654 ft/min.
PV = 15,238 × 0.654 ≈ 9,973 psi·fpm — lands just under the 10,000 psi·fpm SYZ guideline threshold, in the “moderate duty” band.
This is within typical range for street/light off-road use, but close enough to the heavy-duty threshold that it’s worth checking the specific liner material’s datasheet before committing to a continuous-duty application.

Related reading: Metallurgy & Quality Control →

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