Rotary 6438. Blade MTD 20" Mulching replaces MTD 942-0740

What It Is

The Rotary 6438 is a 20-inch mulching blade designed to replace MTD 942-0740. It fits mowers with a 20-inch deck, primarily MTD, Cub Cadet, Troy-Bilt, Yard-Man, and other MTD-built brands. The blade’s curved design and extra cutting edges chop clippings finer than standard blades, letting them decompose into the lawn rather than bagging.

Fitment & Compatibility

Before buying, confirm your mower has a 20-inch deck (measure cutting path, not overall width). This blade fits most MTD 942-0740 applications, but also cross-references to Rotary 6438, Oregon 96-511, and Stens 230-200. Check your old blade’s center hole size (should be 1-inch round) and overall length (20 inches). If your mower uses a star-shaped or oval hole, this blade won’t work. Double-check your model number against Rotary’s fitment list—common fits include MTD 11A-020B, 11A-020E, and Cub Cadet SC 300 series. Avoid relying solely on “fits MTD” claims; measure your existing blade.

Key Things to Know

• Quality: Made from heat-treated steel with a zinc coating for rust resistance. Reviews note it’s slightly thinner than OEM MTD blades but holds an edge well for residential use.
• Installation: Easy bolt-on swap. Use a torque wrench to tighten the center bolt to 35–45 ft-lbs (check your manual). Never reuse the old bolt—buy a new one if yours is worn or stripped.
• Mulching vs. Bagging: This blade is for mulching only. If you want to bag or side-discharge, you’ll need a standard lift blade. Using this blade for bagging will produce poor results.
• Common Gotcha: Some users report the blade is slightly lighter than OEM, which can cause vibration if your mower’s spindle is out of balance. Always balance the new blade before installing.

Should You Buy It

If you have an MTD-built 20-inch mower and want to mulch leaves or grass clippings without bagging, this blade is a solid, budget-friendly upgrade. It’s not for commercial use or heavy-duty mulching, but for typical residential lawns it performs well and saves you from buying OEM at a higher price. Skip it if your mower requires a specific hole shape or you need a bagging blade.