Air & gas bearings: selection requirements and data limits

Aerostatic versus aerodynamic: where does the pressure come from?

Aerostatic bearings receive pressurized gas through a restrictor and can support a stationary load with the supply maintained. Aerodynamic bearings develop supporting pressure through motion; start-up and coast-down require separate checks. Air is one possible working gas.

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This is a mechanism comparison, not a validated foil-bearing or gas-journal design solver.

Reference basis: New Way Design and Application Guide, Revision F, May 2021, mechanism and load discussion; NASA/TM-2007-214691 abstract, 2007. Reviewed 2026-10-02.

Porous carbon, flat pads and shaft air bushings

In a porous-media bearing, interconnected pores meter gas through the bearing face. Porous carbon is the flow-restricting material, not a carbon ball-bearing cage or lubricant additive. A flat pad works against a guide surface; a tubular air bushing surrounds a round shaft for linear motion or rotation. An ordinary radial bushing does not by itself specify an axial thrust constraint.

New Way lists separate thrust-bushing and modular radial-bearing arrangements. Record the shaft, mounting block, alignment method and thrust restraint with the bearing identity. Do not assume that a ball-bushing housing is automatically an approved retrofit.

Reference basis: New Way Air Bushings technical overview; New Way S105001 product specifications. Reviewed 2026-10-02.

A real flat-pad record: New Way S105001

The current product specification identifies S105001 as a 50 mm flat round bearing with an anodized-aluminum housing and porous-carbon face. The manufacturer labels its load as ideal load, not a rolling-bearing dynamic rating C.

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The same page lists a 0.689 MPa maximum supply pressure. That limit is not the condition for the 333 N load above and is not permission to scale load linearly.

Reference basis: New Way S105001 product specifications. Reviewed 2026-10-02.

Load capacity and stiffness are different checks

Supply pressure multiplied by pad area is not a rated usable load: edge leakage and the restrictor create a nonuniform pressure distribution. Use the model's lift/load curve at the intended pressure, gap and preload. A stiffness value describes a local change in force per change in displacement; it is not constant over the entire gap range.

For illustration only, a small 10 N load increment at a locally applicable stiffness of 58 N/µm corresponds to about 0.172 µm displacement (10 ÷ 58). This linearized estimate does not establish safe total load, moment capacity, stability or a new operating gap.

A custom design also needs gas properties, restrictor geometry, clearance, load distribution and dynamic validation. The rolling-bearing life calculator cannot supply an air-bearing life rating.

Reference basis: New Way Design and Application Guide, Revision F, May 2021, mechanism and load discussion; New Way S105001 product specifications. Reviewed 2026-10-02.

PI rotary-air modules: compare axial, radial and moment limits

PI's A-60x PIglide RT modules are nonmotorized rotary supports; a motor or encoder is a separate configuration choice. These manufacturer capacities assume 80 psi supply. Platform diameter and journal length are not rolling-bearing bore and width.

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Precision depends on mounting, payload, orientation and external forces. Published precision figures are static; encoder choice and imbalance may limit speed. A diameter match does not establish equivalent performance.

Reference basis: PI A-60x PIglide RT specifications and footnotes. Reviewed 2026-10-02.

What does vacuum preload do?

A vacuum-preloaded pad combines a positive-pressure supporting region with a vacuum hold-down region. The opposing force changes the operating gap and stiffness and can avoid a second opposed guide surface. Vacuum does not replace the compressed-air supply. Its hold-down force is not an additional payload rating.

New Way identifies S205001 (50 mm), S207501 (75 mm) and S209001 (90 mm) in this family. Their listed hold-down forces at 50.7 kPa are 73, 180 and 260 N respectively. These are vacuum-condition values, not the ideal-load figures of same-diameter ordinary flat pads.

Record both supplies, allowable gap, payload and any orientation or power-loss restraints before choosing the arrangement.

Reference basis: New Way Vacuum Preloaded Air Bearings specifications. Reviewed 2026-10-02.

CMMs, linear stages, rotary tables and spindles

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An air pad is not a complete positioning stage. These are application distinctions, not a Westwind spindle catalogue, a motor design or a guaranteed accuracy claim.

Reference basis: New Way, The State of Air Bearings and Metrology, July 2022; New Way Air Bushings technical overview; PI A-60x PIglide RT specifications and footnotes. Reviewed 2026-10-02.

Air quality and guide surfaces belong in the specification

New Way's care guidance requires clean, dry supply air and warns against operating its bearings without applied air pressure. Oil, water and other contamination are not substitutes for lubrication. Keep the bearing face and guide free of debris; pressure and flow must be available at the component, not only at the compressor.

Its published cleaning instructions specify 70% isopropyl alcohol, prohibit ketones and require complete evaporation before motion over cleaned surfaces. Those instructions are product-specific; they are not a universal cleaning recipe for coatings, plastics, seals or another manufacturer's stage. Follow the machine's safe access procedure and keep hands clear of moving axes.

Do not transfer these pressure or cleaning instructions to a magnetic bearing, air caster, foil bearing or an unidentified spindle.

Reference basis: New Way Care and Air instructions. Reviewed 2026-10-02.

Air casters for moving equipment are a different product class

Air casters, air skates and air dollies create a film between a load-carrying device and the floor. They support material handling, not a precision shaft journal. Floor condition, load distribution, restraint and the complete air supply matter; a large kit capacity cannot be assigned to each individual skid.

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The manufacturer lists these separately. Kit selection still requires a reviewed moving plan and floor conditions; this table is not a rigging or lifting authorization.

Reference basis: Airfloat Air Skid Sets model tables. Reviewed 2026-10-02.