LiftMaster 71-1550B18QGH Drive Sprocket — 18 Teeth, #50 Chain, 1-1/4-Inch Bore
LiftMaster 71-1550B18QGH Drive Sprocket — 18 Teeth, #50 Chain, 1-1/4-Inch Bore
The LiftMaster 71-1550B18QGH is an 18-tooth drive sprocket for #50 roller chain, with a 1-1/4-inch bore and a 1/4-inch keyway. It is a replacement mechanical drive component for an assembly that specifies this exact sprocket configuration. Match the complete part number, shaft size and original drive arrangement before ordering. Tooth count and bore size both matter: a sprocket that accepts the same chain can still have the wrong shaft fit or alter the original drive ratio.
Compatibility — Models, Versions and Exclusions
| Model or selection point | Compatibility requirement |
|---|---|
| Exact documented replacement | Use where the equipment parts list specifies this complete reference or an approved equivalent. |
| #50 chain | Correct chain family, but chain size alone does not establish operator or shaft compatibility. |
| Other 1-inch-bore sprockets | A smaller bore does not fit the specified 1-1/4-inch shaft; matching chain family and tooth count cannot correct that difference. |
| Other tooth counts or bore sizes | Do not substitute without approval for the complete drive assembly. |
Match Shaft Fit and Drive Geometry
This QGH version has the larger 1-1/4-inch bore. The 18-tooth LGH version uses a 1-inch bore, while the 32-tooth QGH version shares the larger bore but changes tooth count. Neither is established as a substitute for this exact configuration. Keep both dimensions visible when ordering, especially if an old invoice abbreviates the part number or describes only the chain size.
The sprocket must sit in the correct chain line and be secured by the specified shaft, key and retention arrangement. Have the technician inspect the shaft and keyway for wear as well as the teeth. A damaged shaft, loose mounting or misaligned chain can cause recurring trouble after a new sprocket is installed. Photograph the existing assembly before parts are removed so its position and neighboring components can be identified.
Specifications and Product Identification
| Specification | Details |
|---|---|
| Manufacturer part number | 71-1550B18QGH |
| Sprocket designation | 50B18 |
| Tooth count | 18 |
| Chain family | #50 roller chain |
| Bore diameter | 1-1/4 inch |
| Keyway | 1/4 inch |
| Retention | Manufacturer description specifies set screws; confirm supplied hardware |
Before Ordering
- Record the complete operator model and the sprocket part number from its service diagram.
- Confirm 18 teeth, #50 chain, a 1-1/4-inch shaft fit and the specified keyway.
- Check hub clearance, chain alignment and the required shaft-retention arrangement.
- Inspect the chain, connecting link, mating sprockets and shaft for related wear.
Package Contents and Separate Requirements
This listing identifies the sprocket. Do not assume that roller chain, a connecting link, shaft key, shaft or every mounting fastener is included. Verify the current supplier package and obtain the separate components needed for the repair. The set-screw reference is a retention detail; it should not be interpreted as a stainless-steel material specification or a corrosion-resistance guarantee.
Safety Warnings — Read Before Installation or Service
- WARNING: An exposed chain drive can trap fingers or clothing and cause serious injury. Replacement requires a qualified door- or gate-systems technician.
- Isolate and secure all applicable power sources and prevent unexpected movement before working on the chain drive.
- Do not change tooth count, enlarge the bore or improvise the shaft connection to make an unmatched part fit.
- Restore guards, verify chain alignment and complete the equipment’s prescribed operating and safety tests before returning it to service.
Related Products and Important Differences
- #50 roller chain, 10-foot length — a chain-family match; determine the required length and installation suitability.
- #50 chain master link — select the correct connecting link for the actual chain; not interchangeable with a #41 link.
- 71-1550B32QGH 32-tooth sprocket with 1-1/4-inch bore — a different tooth-count comparison, not an approved replacement for this 18-tooth sprocket.
Frequently Asked Questions
Will any #50 sprocket fit?
No. Chain size, tooth count, bore, keyway, hub clearance and the approved drive arrangement must all match.
Can I change tooth count to make the opening move faster?
Do not use a service replacement to change operating speed. Any ratio change requires approval for the complete equipment and its safety system.
Should I inspect the chain at the same time?
Yes. A technician should evaluate wear, alignment and the mating components so a worn chain does not undermine the repair.
Does this listing include a shaft key and new chain?
These are not promised as included. Confirm the supplied contents and order the separately required parts for the documented repair.
Need Help Confirming the Right Product?
Contact Garage-DoorParts.com before ordering. Send the full equipment model, readable part labels and photographs of the installed assembly. Include the dimensions, electrical configuration or accessory details relevant to your project so the listing can be checked against the actual installation.
Details
Need Help With Compatibility?
Not sure if this is the correct part for your garage door, operator, gate system, or application? Contact Us before ordering — we’re happy to help.
Garage-DoorParts.com carries a large selection of residential and commercial parts, and many components can look similar while having important differences in dimensions, model numbers, voltage, mounting, or compatibility.
For the best assistance, please provide as much information as possible, including the manufacturer, model number, part number, door or operator type, dimensions, and clear photos of the existing part or equipment.
Our goal is to help you identify the correct product before you order and reduce the possibility of ordering an incompatible part.
Contact Us with your product questions and compatibility information, and we’ll do our best to point you in the right direction.
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