{"product_id":"liftmaster-71-1550b18lgh","title":"LiftMaster 71-1550B18LGH 18-Tooth #50 Chain Sprocket Kit – 1-Inch Bore","description":"\u003cp\u003e\u003cstrong\u003eThe LiftMaster 71-1550B18LGH is a 50B18 sprocket kit for a compatible chain-driven operator installation. It combines an 18-tooth #50-chain sprocket with a 1-inch bore and a 1\/4-inch key specification. Use the exact part number and required drivetrain dimensions when selecting a replacement. This is a mechanical service component for a correctly matched shaft and chain path. The bore, keyed connection, tooth count and mounting geometry all matter, so compare the original assembly before treating another sprocket with similar headline dimensions as an equivalent.\u003c\/strong\u003e\u003c\/p\u003e\u003ch2\u003eCompatibility — Models, Versions and Exclusions\u003c\/h2\u003e\u003ctable\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth\u003eModel or selection point\u003c\/th\u003e\n\u003cth\u003eCompatibility requirement\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003e#50 chain\u003c\/td\u003e\n\u003ctd\u003eRequired chain family; tooth count alone is insufficient.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e18 teeth\u003c\/td\u003e\n\u003ctd\u003eMatch the specified drive ratio for the equipment.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e1-inch bore \/ 1\/4-inch key\u003c\/td\u003e\n\u003ctd\u003eBoth shaft diameter and keyed connection must match.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOperator fit\u003c\/td\u003e\n\u003ctd\u003eRequires the original part reference or verified dimensional and installation requirements.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDifferent hub or offset\u003c\/td\u003e\n\u003ctd\u003eRequires an additional fit check even when tooth count and bore match.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\u003ch2\u003eA Matching Tooth Count Is Only the Beginning\u003c\/h2\u003e\u003cp\u003eThis part must fit both the shaft and the chain path. A mechanically plausible fit can still be wrong if the hub position moves the sprocket out of alignment, the key does not engage correctly or there is insufficient clearance. Compare the original assembly and the equipment drawing before treating another 50B18 sprocket as an equivalent.\u003c\/p\u003e\u003cp\u003eDescribe the replacement as a drivetrain repair, not a speed upgrade. Changing tooth count changes the drive relationship and may affect the equipment’s operation. A worn sprocket should also prompt inspection of the chain, mating sprocket, shaft and keyway so that damage elsewhere is not overlooked. The appropriate repair depends on the complete assembly, not only this one component.\u003c\/p\u003e\u003ch2\u003eSpecifications\u003c\/h2\u003e\u003ctable\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth\u003eSpecification\u003c\/th\u003e\n\u003cth\u003eDetails\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eManufacturer part number\u003c\/td\u003e\n\u003ctd\u003e71-1550B18LGH\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSprocket designation\u003c\/td\u003e\n\u003ctd\u003e50B18\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eChain size\u003c\/td\u003e\n\u003ctd\u003e#50\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTooth count\u003c\/td\u003e\n\u003ctd\u003e18\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBore\u003c\/td\u003e\n\u003ctd\u003e1 inch\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eKey specification\u003c\/td\u003e\n\u003ctd\u003e1\/4 inch\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCatalog configuration\u003c\/td\u003e\n\u003ctd\u003eSprocket kit with set screw\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\u003ch2\u003eHow to Choose the Correct Sprocket\u003c\/h2\u003e\u003cp\u003eCheck the chain size, tooth count, shaft diameter, key dimensions and mounting arrangement together. A sprocket with the right bore but a different tooth count changes the drive relationship. A similar-looking sprocket for another chain size is not an equivalent replacement.\u003c\/p\u003e\u003cul\u003e\n\u003cli\u003eMatch the operator or installation parts list to 71-1550B18LGH.\u003c\/li\u003e\n\u003cli\u003eConfirm a 1-inch shaft fit and the specified keyed connection.\u003c\/li\u003e\n\u003cli\u003eCompare sprocket alignment and clearance with the original installation.\u003c\/li\u003e\n\u003cli\u003eHave worn chain and mating sprockets assessed during replacement.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\u003ch3\u003eWill a 1-1\/4-inch bore version fit the same shaft?\u003c\/h3\u003e\u003cp\u003eIt is a different bore configuration. Order the version specified for the actual shaft and approved installation.\u003c\/p\u003e\u003ch3\u003eDoes this kit include a complete chain drive?\u003c\/h3\u003e\u003cp\u003eThis item is identified as a sprocket kit. Confirm any required chain, shaft, keys or additional mounting hardware separately.\u003c\/p\u003e\u003ch2 class=\"safety-warning\"\u003eSafety Warnings — Read Before Installation or Service\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003eWARNING: Exposed chains, sprockets and shafts can catch clothing or fingers and cause serious injury. Never inspect or adjust them while powered equipment can move.\u003c\/li\u003e\n\u003cli\u003eDisconnect and secure operator power, including backup supplies, and secure the door or gate before drivetrain work.\u003c\/li\u003e\n\u003cli\u003eDo not loosen or disturb a door’s spring or counterbalance system as part of an unqualified sprocket replacement.\u003c\/li\u003e\n\u003cli\u003eHave the technician verify alignment, retention and chain condition, restore guards, and complete the operator’s required operational and safety checks.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eRelated Products and Important Differences\u003c\/h2\u003e\u003cul\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/garage-doorparts.com\/products\/18-tooth-1-bore-14-keyway-50b18\"\u003e50B18 sprocket — 18 teeth, #50 chain, 1-inch bore\u003c\/a\u003e — a dimensional comparison listing. Matching headline dimensions do not establish the same manufacturer kit, hub geometry or hardware package.\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/garage-doorparts.com\/products\/18-tooth-1-bore-14-keyway\"\u003e18-tooth #41-chain sprocket\u003c\/a\u003e — a different chain family. It illustrates why matching the bore and tooth count is not enough; it is not the #50-chain substitute.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch2\u003eMore Questions Before Ordering\u003c\/h2\u003e\u003ch3\u003eIs any 50B18 sprocket the same as this LiftMaster kit?\u003c\/h3\u003e\u003cp\u003eNot automatically. Verify the full dimensions, hub configuration, material requirements and supplied hardware, along with the equipment manufacturer’s replacement specification.\u003c\/p\u003e\u003ch3\u003eCan I reuse the old key and set screw?\u003c\/h3\u003e\u003cp\u003eHave the technician inspect the shaft connection and use the hardware specified for the replacement. The condition of the old components cannot be established from the product number.\u003c\/p\u003e\u003ch2\u003eNeed Help Confirming the Right Part?\u003c\/h2\u003e\u003cp\u003e\u003ca href=\"https:\/\/garage-doorparts.com\/pages\/contact\"\u003eContact Garage-DoorParts.com before ordering\u003c\/a\u003e. Send the full operator model, readable part labels and photographs of the installed assembly. Include dimensions or the control-box model where relevant. We can help compare the listing with the information you provide; final installation suitability should be confirmed by the servicing technician.\u003c\/p\u003e","brand":"LiftMaster","offers":[{"title":"Default Title","offer_id":60655763915038,"sku":"71-1550B18LGH","price":45.15,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0978\/2781\/5710\/files\/71-1550b18lgh.png?v=1793139838","url":"https:\/\/garage-doorparts.com\/products\/liftmaster-71-1550b18lgh","provider":"garage-doorparts.com","version":"1.0","type":"link"}