M170642 Mulching Blades for 42" John Deere Z335E Z335M Z345M Z345R X350 X354 X370 X380 S220 Mower Deck (2 Pack)

What It Is

These M170642 mulching blades are a 2-pack of replacement blades designed for 42-inch John Deere mower decks. They chop grass clippings into fine particles that decompose quickly, ideal for homeowners who want to skip bagging and leave clippings on the lawn.

Fitment & Compatibility

Before buying, verify your mower deck is exactly 42 inches (measured blade tip to tip). These fit John Deere Z335E, Z335M, Z345M, Z345R, X350, X354, X370, X380, and S220 models with the 42-inch deck. They are a direct replacement for OEM M170642 blades. Check your current blade’s center hole size—these use a 1-inch diameter hole with a 5-point star drive pattern. Measure your blade length (should be 21 inches) and thickness (0.203 inches) to confirm match. Not compatible with 48-inch or 54-inch decks, or non-John Deere brands without adapter kits.

Key Things to Know

• Quality: Made from hardened steel with a painted finish; sharp out of the box but expect to sharpen after 10-15 hours of use on thick grass.
• Installation: Easy DIY job—remove the deck, use a socket wrench (typically 15/16" or 5/8" bolt), and torque to 45-55 ft-lbs. Wear gloves; edges are sharp.
• Gotcha: These are mulching blades, not standard lift blades. They won’t discharge clippings well if you leave the chute open—use the included mulch plug or cover.
• Common issue: The star drive pattern can wear over time; replace the bolts if they’re stripped to prevent blade detachment.

Should You Buy It

Buy these if you own one of the listed John Deere 42-inch deck models and want to mulch clippings into fine, nutrient-rich compost for your lawn. They’re a solid value at $32 for a 2-pack, but skip them if you prefer side-discharge or bagging—these blades are optimized for recirculating clippings, not throwing them out.