Arnold OEM-742-0620 20-Inch MTD Lawn Mower Blade Mulching Lawn Mower Blade Replaces 742-0620/742-0520

What It Is

This is a 20-inch mulching blade designed for MTD-branded lawn mowers. It replaces OEM part numbers 742-0620 and 742-0520, and is intended to cut grass into fine clippings that decompose quickly, eliminating the need for bagging.

Fitment & Compatibility

Before buying, confirm the following:

• Deck size: This blade is exactly 20 inches long. Measure your current blade from tip to tip. If your deck is 20 inches, it fits. If your deck is 21 or 22 inches, this blade is too short.
• Model/brand fit: Works with most MTD, Cub Cadet, Troy-Bilt, Yard Machines, and Yard-Man mowers that use a 20-inch blade. Check your mower’s model number against Arnold’s fitment list online.
• OEM vs aftermarket: Arnold is an aftermarket replacement, not an OEM MTD part. It matches the original specs but may differ slightly in shape or balance.
• Center hole and offset: The center hole is 5/8-inch diameter with a 1-inch offset. Measure your spindle and blade adapter to be sure.

Key Things to Know

• Mulching performance: The curved, high-lift design creates suction to recut clippings. It works best with a mulching plug installed and dry grass. Wet or tall grass may clump.
• Installation: Requires a torque wrench set to 40-50 ft-lbs. Use new blade bolts or Loctite to prevent loosening. The blade must be mounted with the lift wings facing up toward the deck.
• Sharpening: Can be sharpened 2-3 times before replacement. Always sharpen both ends equally to maintain balance. An unbalanced blade causes vibration and deck damage.
• Common gotcha: This blade is not compatible with side-discharge or bagging-only mowers unless you remove the mulching plug. It’s a dedicated mulching blade.

Should You Buy It

If you have an MTD-style mower with a 20-inch deck and want to mulch leaves or grass without bagging, this blade is a solid, budget-friendly upgrade. It’s well-reviewed and easy to install, but double-check your mower’s model number and blade offset first to avoid a return.