Castair SK158 — Replacement Motor SK Hub, 1-5/8" Shaft
The Castair SK158 is a replacement SK-series motor hub for motors with a 1-5/8-inch output shaft used in Cast Air compressor configurations that specify the SK hub style. The SK designation is critical — Cast Air uses two distinct hub series (SK and SD) on different compressor models, and they are not interchangeable. If your compressor uses an SK hub and your motor shaft measures 1-5/8 inches in diameter, the SK158 is the correct replacement part.
On belt-driven compressors, the motor hub connects the motor's output shaft to the drive sheave and V-belt system that transfers power to the compressor pump. This component takes the full torque load at every startup and throughout operation. Hub failures — cracked bodies, worn bores, stripped keyways — cause vibration, belt misalignment, and eventually a compressor that cannot run correctly. The repair is a direct hub replacement with the correct OEM part.
How to Confirm You Need the SK158
- Hub Series: Check your existing hub for a part number stamp. If it shows SK158, SK158, or simply "SK" with a 158 designation, this is your replacement
- Shaft Diameter: Measure the motor output shaft with a caliper. A 1-5/8-inch shaft measures 1.625 inches in decimal. If your shaft is 1-7/8 inches (1.875"), you need the SK178 instead
- If Unsure: Call us at 866-217-0063 with your compressor model number and we will confirm the correct hub before you order
Key Features
- SK Series Hub: Designed for Cast Air compressors specifying SK-series motor hubs — distinct mounting interface from SD-series hubs used on other models
- 1-5/8-Inch Shaft Bore: Machined to fit a 1-5/8-inch motor output shaft — precision bore ensures concentric running and eliminates shaft slop
- OEM Cast Air Replacement: Manufactured to original Cast Air specifications — same tolerances as the original hub
- Belt-Drive Application: Transmits motor torque to the belt-drive pulley system for compressor pump operation
- Direct Replacement: No machining, modification, or additional hardware required for compatible Cast Air SK-hub applications
Technical Specifications
- Part Number: SK158
- Hub Series: SK
- Shaft Diameter: 1-5/8 inch (1.625")
- Component Type: Replacement motor drive hub
- Manufacturer: Cast Air (Castair)
- Price: $52.36
Cast Air Motor Hub Lineup — Full Series Reference
- SD138 — SD series, 1-3/8" shaft ($31.57)
- SD158 — SD series, 1-5/8" shaft ($31.57)
- SK158 — SK series, 1-5/8" shaft ($52.36). This product.
- SK178 — SK series, 1-7/8" shaft ($52.36)
SD and SK hubs are different series. The shaft diameter alone does not determine which hub you need — both SD158 and SK158 fit a 1-5/8-inch shaft, but they are different parts designed for different compressor configurations. Confirm your hub series before ordering.
When Does a Shop Need the SK158
Replace the motor hub when:
- The existing SK hub is cracked, the bore is worn out of round, or the keyway is damaged
- The compressor produces vibration at startup or during operation — often a hub that has loosened on the shaft
- Belt alignment problems persist despite correct tension — worn hub bore causes pulley runout
- Replacing a motor where the replacement motor has a 1-5/8-inch output shaft in an SK-hub application
- Preventive maintenance stocking for Cast Air SK-hub equipment
Why Buy From Air Compressor Factory Direct?
- Authorized Cast Air dealer since 2016
- Free shipping on qualifying orders
- Free technical support at 866-217-0063 — we can confirm hub series and shaft size before you order
- Full manufacturer warranty
Call 866-217-0063 for quick answers and help!
