{"product_id":"castair-replacement-motor-sk-hub-1-7-8-shaft-sk178","title":"Castair Replacement Motor SK Hub 1 7\/8\" Shaft SK178","description":"\u003ch2\u003eCastair SK178 — Replacement Motor SK Hub, 1-7\/8\" Shaft\u003c\/h2\u003e\n\n\u003cp\u003eThe Castair SK178 is a replacement SK-series motor hub for motors with a 1-7\/8-inch output shaft — the largest shaft diameter in the Cast Air SK hub range. This hub is used on Cast Air compressor configurations in the upper HP range where the motor output shaft steps up to 1-7\/8 inches. If your compressor uses an SK-series hub and the motor shaft measures 1-7\/8 inches in diameter, the SK178 is your replacement part. The smaller SK158 (1-5\/8\") will not fit.\u003c\/p\u003e\n\n\u003cp\u003eAs with all belt-drive motor hubs, confirming the hub series (SK vs. SD) and measuring the shaft diameter accurately are critical before ordering. A hub that is 1\/4 inch off in shaft diameter will not seat, and an SK hub on an SD application (or vice versa) is not an acceptable substitute regardless of shaft size. Call us if you are unsure — this is exactly the kind of question we answer before you order.\u003c\/p\u003e\n\n\u003ch3\u003eWhat the Motor Hub Does\u003c\/h3\u003e\n\u003cp\u003eThe motor hub mounts to the electric motor's output shaft and carries the drive sheave that transmits torque to the compressor pump via V-belt. On every startup, the hub absorbs the full torque spike of the motor coming up to speed. Over time in continuous commercial service, hub bores wear out of round, keyways enlarge, or the hub body cracks from fatigue and vibration. Any of these failures cause vibration, belt slippage, and misalignment problems. Replacing the hub with the correct OEM part resolves these issues cleanly.\u003c\/p\u003e\n\n\u003ch3\u003eKey Features\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSK Series Hub:\u003c\/strong\u003e For Cast Air compressors specifying SK-series motor hubs — not interchangeable with SD-series hubs used on other configurations\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e1-7\/8-Inch Shaft Bore:\u003c\/strong\u003e The largest shaft diameter in the Castair SK hub range — machined precisely for a 1-7\/8-inch (1.875\") motor output shaft\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eOEM Cast Air Replacement:\u003c\/strong\u003e Manufactured to original Cast Air specifications\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBelt-Drive Application:\u003c\/strong\u003e Transmits motor torque to the belt-drive system — sized for higher-HP Cast Air compressor motor configurations\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eDirect Replacement:\u003c\/strong\u003e Designed for direct installation on SK-hub compressor configurations without modification\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eTechnical Specifications\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e SK178\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eHub Series:\u003c\/strong\u003e SK\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eShaft Diameter:\u003c\/strong\u003e 1-7\/8 inch (1.875\")\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eComponent Type:\u003c\/strong\u003e Replacement motor drive hub\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eManufacturer:\u003c\/strong\u003e Cast Air (Castair)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePrice:\u003c\/strong\u003e $52.36\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eCast Air Motor Hub Lineup — Full Series Reference\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSD138\u003c\/strong\u003e — SD series, 1-3\/8\" shaft ($31.57)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSD158\u003c\/strong\u003e — SD series, 1-5\/8\" shaft ($31.57)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSK158\u003c\/strong\u003e — SK series, 1-5\/8\" shaft ($52.36)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSK178\u003c\/strong\u003e — SK series, 1-7\/8\" shaft ($52.36). This product.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhen Does a Shop Need the SK178\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eReplace the motor hub when:\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eThe SK hub on a larger Cast Air compressor is cracked, the bore is worn, or the keyway is damaged\u003c\/li\u003e\n  \u003cli\u003eThe compressor vibrates at startup or during operation — a common symptom of a hub that has loosened on the shaft\u003c\/li\u003e\n  \u003cli\u003eBelt misalignment persists despite correct tension — worn hub bore causing pulley runout\u003c\/li\u003e\n  \u003cli\u003eInstalling a replacement motor with a 1-7\/8-inch output shaft on an SK-hub compressor configuration\u003c\/li\u003e\n  \u003cli\u003ePreventive maintenance stocking for facilities running Cast Air equipment in the upper HP range\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhy Buy From Air Compressor Factory Direct?\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\u003cstrong\u003eAuthorized Cast Air dealer since 2016\u003c\/strong\u003e\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFree shipping\u003c\/strong\u003e on qualifying orders\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFree technical support\u003c\/strong\u003e at 866-217-0063 — we can confirm hub series and shaft size from your compressor model number\u003c\/li\u003e\n  \u003cli\u003e\u003cstrong\u003eFull manufacturer warranty\u003c\/strong\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003e\u003cstrong\u003eCall 866-217-0063 for quick answers and help!\u003c\/strong\u003e\u003c\/p\u003e","brand":"Cast Air","offers":[{"title":"Default Title","offer_id":53342602395861,"sku":"SK178","price":96.56,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0622\/8466\/0949\/files\/CastairReplacementAirCompressorMotorHub_ab3992a7-e095-461f-b0ab-f96441df37be.png?v=1772652936","url":"https:\/\/aircompressorfactorydirect.com\/products\/castair-replacement-motor-sk-hub-1-7-8-shaft-sk178","provider":"Air Compressor Factory Direct","version":"1.0","type":"link"}