{"product_id":"castair-replacement-motor-pulley-5-8-fixed-bore-shaft-4-od-1a-groove-p1a40-5-8","title":"Castair Replacement Motor Pulley 5\/8\" Fixed Bore Shaft 4\" OD. 1A Groove P1A40-5\/8","description":"\u003ch2\u003eCast Air P1A40-5\/8 — 4\" OD Single-Groove A-Section Motor Pulley, 5\/8\" Fixed Bore\u003c\/h2\u003e\n\n\u003cp\u003eThe Cast Air P1A40-5\/8 is a 4\" outside diameter motor pulley with a single A-section belt groove and a 5\/8\" fixed bore. It mounts directly onto a 5\/8\" motor shaft — no separate hub required — and drives an A-section V-belt to the compressor pump pulley. This is a common motor pulley size on fractional-horsepower and small single-phase compressors. If your existing pulley is cracked, the bore is wallowed out, or a keyway has stripped, this is a direct replacement for any Cast Air or compatible compressor that uses a 5\/8\" motor shaft and an A-belt drive.\u003c\/p\u003e\n\n\u003cp\u003eGetting the pulley selection right matters for compressor performance. The motor pulley diameter — in combination with the pump pulley diameter — sets the pump RPM. Too small a motor pulley and the pump runs slower than designed, reducing output CFM. Too large and the pump runs overspeed, increasing wear and potentially overloading the motor. The P1A40-5\/8 is a 4\" motor pulley, which is a standard size for this class of compressor. If you are replacing like-for-like, match the 4\" OD and 1A groove specification to your existing pulley.\u003c\/p\u003e\n\n\u003ch3\u003ePulley Specifications\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e P1A40-5\/8\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eOutside Diameter:\u003c\/strong\u003e 4\"\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBore Size:\u003c\/strong\u003e 5\/8\" fixed bore (no hub required)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eGroove Type:\u003c\/strong\u003e 1A — single groove, A-section belt profile\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBelt compatibility:\u003c\/strong\u003e A-section V-belt (e.g., A-29, A-31, A-34 — belt length depends on center distance)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMounting:\u003c\/strong\u003e Fixed bore — mounts directly on 5\/8\" motor shaft with setscrew\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMaterial:\u003c\/strong\u003e Cast iron (standard for compressor drive pulleys)\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eA-Section vs. B-Section Belt Grooves — Why It Matters\u003c\/h3\u003e\n\u003cp\u003eA-section and B-section belts are not interchangeable. The groove profile (angle and depth) is different between the two belt sizes. Running an A-belt in a B-groove or vice versa results in the belt riding too high or too low in the groove, causing slippage, rapid belt wear, and pulley wear.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eA-section belt:\u003c\/strong\u003e 1\/2\" wide at the top, used on lighter-duty drives and smaller compressors\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eB-section belt:\u003c\/strong\u003e 21\/32\" wide at the top, used on heavier-duty drives and larger compressors\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMatch the groove to the belt already on your compressor.\u003c\/strong\u003e If your compressor shipped with an A-belt, use the P1A40-5\/8. If it shipped with a B-belt, you need the P1B40-5\/8 instead.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eFixed Bore vs. Hub Pulleys\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFixed bore (this pulley):\u003c\/strong\u003e The bore is machined to a specific size — in this case 5\/8\". The pulley mounts directly on the shaft. No hub is ordered separately. Simple, common, and lower cost.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eHub pulleys:\u003c\/strong\u003e Bore is not machined — a separate hub (LX, SD, or SK series) is ordered to match your shaft size and pressed or bolted into the pulley. Used when the same pulley needs to fit different shaft sizes.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eIf your motor shaft is 5\/8\":\u003c\/strong\u003e The P1A40-5\/8 mounts directly. No additional parts needed beyond a key and setscrew (typically included or already on the shaft).\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhen to Replace the Motor Pulley\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCracked pulley body:\u003c\/strong\u003e A cracked cast iron pulley is a safety hazard. Replace it immediately — do not run a cracked pulley under tension.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eWorn or damaged keyway:\u003c\/strong\u003e If the keyway is chipped, rounded, or the key spins in the slot, the pulley is slipping on the shaft. You may hear squealing during startup or notice the pump not keeping up with demand.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eWallowed bore:\u003c\/strong\u003e A bore that has worn oversize — common when the pulley has run without a key — cannot be fixed by tightening the setscrew. Replace the pulley.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eGroove wear:\u003c\/strong\u003e A groove that has worn to a rounded profile allows the belt to slip under load. If the belt is in good condition but still slips at full load, measure the groove depth and compare to a new pulley.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBelt replacement:\u003c\/strong\u003e When replacing a belt after extended service, inspect the pulley groove for wear at the same time.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eBelt Guard Compatibility\u003c\/h3\u003e\n\u003cp\u003eCast Air motor pulleys are used with specific belt guards depending on the compressor model. For reference, the 2BG guard (24x16x5) is used with Cast Air models A2, A3, A4, and A8. If you are ordering a replacement pulley for one of these models, confirm that a 4\" OD motor pulley matches the original specification before ordering.\u003c\/p\u003e\n\n\u003ch3\u003eAvailable Motor Pulleys in This Series\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eP1A40-5\/8 (this pulley):\u003c\/strong\u003e 4\" OD, 5\/8\" bore, 1A groove — $30.80\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eP1B40-5\/8:\u003c\/strong\u003e 4\" OD, 5\/8\" bore, 1B groove — $30.80\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eP1B40-7\/8:\u003c\/strong\u003e 4\" OD, 7\/8\" bore, 1B groove\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eP2B series:\u003c\/strong\u003e Dual B-groove pulleys in multiple OD and shaft size combinations for larger compressors\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 P1A40-5\/8\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eOutside Diameter:\u003c\/strong\u003e 4.0\"\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBore:\u003c\/strong\u003e 5\/8\" fixed bore\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNumber of Grooves:\u003c\/strong\u003e 1\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eGroove Profile:\u003c\/strong\u003e A-section\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBore Type:\u003c\/strong\u003e Fixed (no hub required)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMaterial:\u003c\/strong\u003e Cast iron\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePrice:\u003c\/strong\u003e $30.80\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhy Buy From Air Compressor Factory Direct?\u003c\/h3\u003e\n\u003cp\u003eWe specialize in Cast Air compressor parts and have the full lineup of motor pulleys in stock. When you call us before ordering, we can confirm the right pulley for your specific compressor model — the right OD, the right bore, and the right groove profile — so you are not guessing and hoping it fits. A wrong pulley means another order, more downtime, and more frustration. We would rather spend two minutes on the phone helping you get it right the first time.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFree shipping\u003c\/strong\u003e on qualifying orders\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFree tech support:\u003c\/strong\u003e Call 866-217-0063 — we will help you identify the correct pulley for your compressor\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFull manufacturer warranty\u003c\/strong\u003e on all parts\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eHonest guidance:\u003c\/strong\u003e If you need to know the original pulley spec for your Cast Air model, call us and we will look it up\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":53342572839125,"sku":"P1A40-5\/8","price":56.8,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0622\/8466\/0949\/files\/MOTOR-PULLEYS-300x248_421ad4fe-fabf-4c69-8aa4-d319edc1cde4.jpg?v=1772652758","url":"https:\/\/aircompressorfactorydirect.com\/products\/castair-replacement-motor-pulley-5-8-fixed-bore-shaft-4-od-1a-groove-p1a40-5-8","provider":"Air Compressor Factory Direct","version":"1.0","type":"link"}