M170642 Lawn Mower Blades for John Deere 42-Inch Deck UC22008 M170639- Includes 2 Bolts and 2 Washers - Fits X330 X350 X354 X370 X380 Z335E Z335M Z345M Z345R,2-Pack

What It Is

This is a 2-pack of 42-inch replacement blades for John Deere lawn tractors and zero-turn mowers, designed for cutting grass on residential or light commercial turf. It includes two bolts and two washers for mounting.

Fitment & Compatibility

• Deck size: Must be a 42-inch (107 cm) John Deere cutting deck. Measure your existing blade length (end to end) to confirm it matches 21 inches per blade (two blades cover the full 42-inch width).
• Model fit: Listed for X330, X350, X354, X370, X380, Z335E, Z335M, Z345M, Z345R. If you have a different John Deere model with a 42-inch deck (e.g., D-series, LA-series), measure blade length and center hole diameter (likely 1-inch or 7/8-inch) before ordering.
• OEM cross-reference: Replaces John Deere part numbers M170639, M170642, and UC22008. The included bolts and washers match OEM specs (likely 5/16-18 x 1 inch bolts with lock washers).
• Measurement check: Blade length should be 21 inches, center hole 1 inch, and thickness about 0.17 inches. Verify your deck’s spindle bolt pattern matches.

Key Things to Know

• Quality: Aftermarket blades, not OEM John Deere. Materials and heat treatment may differ—expect shorter life or faster dulling compared to factory blades.
• Installation: Easy for DIYers—remove old blades, clean spindles, install new blades with included hardware. Torque bolts to 35-50 ft-lbs (check your deck manual). Use a block of wood to prevent blade rotation.
• Common gotcha: The included bolts may be slightly different thread pitch or length than your original hardware. Compare them side-by-side before final tightening. Always replace bolts and washers with new ones (included here) to ensure safe retention.
• Balancing: Aftermarket blades may be unbalanced out of the box. Test by hanging on a nail—if one side dips, file the heavy side slightly. Unbalanced blades cause vibration and wear spindles.

Should You Buy It

If you have a compatible 42-inch John Deere model and want a budget-friendly replacement with hardware included, this is a solid choice for routine mowing. But if you need longer blade life or OEM-grade consistency for heavy or wet grass, consider spending more on genuine John Deere blades.