q&p Spindle Assembly for 50" Mower Deck — Direct-Fit Replacement with Bolt, 5/8"-18 Thread

The q&p Spindle Assembly w/Bolt is a direct-fit replacement spindle that restores blade mounting and rotation on 50" deck MTD and compatible zero-turn mowers.

If a worn or damaged deck spindle is causing vibration, poor cut quality, or preventing blades from threading on properly, this q&p assembly provides the core rotating hub and bolt needed to get the deck back into service. Engineered to replace several OEM part numbers, the unit includes the spindle housing and mounting bolt and is designed for models that use a 50" mowing deck, so you can swap it in without extensive modifications.

Which machines and OEM parts does this replace?

This spindle assembly is manufactured to match the form, fit and function of multiple original-equipment parts from MTD and related brands. It fits a range of 50" deck-equipped residential and commercial lawn tractors and zero-turn models, making it a versatile spare for common maintenance tasks.

• Replaces OEM numbers: MTD 918-06980, 618-06980, 285-707 and equivalent references.
• Compatible models include RZT-L50, LX50, S50, S50KH, XT1-GT50, XT1-ST54 and ZT-L50 with a 50" deck.
• Designed for MTD model frames with parts lists 14A7A3ZQ099 and 17ARCBDQ099.

What are the key dimensions and thread specifications?

Understanding the spindle’s dimensions ensures you order the correct replacement and that the blade and pulley align properly. This q&p unit provides the size and thread pitch commonly used on 50" decks so the pulley, blade and mounting holes line up with factory locations.

• Overall spindle height: 6.8 inches for proper belt and blade clearance.
• Main bolt thread: 5/8"-18 UNF, matching factory blade bolts and hardware.
• Pulley outer diameter (OD): 5.0 inches to maintain belt alignment and tension.
• Mounting holes are tapped for easier installation and accurate torqueing.

How difficult is the installation and what tools are needed?

Installation is straightforward for anyone comfortable with deck service — you’ll remove the deck, take off the old spindle, and bolt in the replacement. Because the mounting holes are tapped and the bolt thread matches common OEM fasteners, reassembly is quicker and requires only basic hand tools.

• Typical tools: socket set, torque wrench, breaker bar, wood block to secure blade during removal.
• No special machining or modification is required—the unit is a direct-replacement design.
• Follow mower manufacturer torque specs for spindle bolts and use thread-lock where recommended.

Who is this for? The q&p Spindle Assembly w/Bolt is intended for homeowners, groundskeepers and small-tractor owners who need a reliable replacement part for 50" deck mowing systems. It’s a good match if you own one of the listed MTD-compatible models and want a cost-effective, OEM-equivalent spindle that simplifies repairs and helps restore proper blade operation and deck performance.