MTD Replacement Part Blade 25mm Adapter

What It Is

The MTD Replacement Part Blade 25mm Adapter is a center-mount adapter that allows a standard mower blade to fit on a 25mm (1-inch) diameter crankshaft. It’s designed for MTD-built lawn tractors, zero-turn mowers, and walk-behind mowers that use a 25mm output shaft.

Fitment & Compatibility

Before buying, check these specifics:

• Shaft diameter: Measure your mower’s crankshaft—must be exactly 25mm (1 inch). If it’s 7/8” or 1-1/8”, this adapter won’t fit.
• Deck size: Works across most MTD decks (42”, 46”, 48”, 50”, 54”, etc.), but the adapter itself doesn’t depend on deck size—only the shaft.
• Brand/model: Fits nearly all MTD, Cub Cadet, Troy-Bilt, and Yard-Man mowers with a 25mm shaft. Check your model number (usually under seat or on frame) and cross-reference with MTD’s parts lookup.
• OEM vs aftermarket: This is an OEM MTD part (not generic), so it matches factory specs exactly. Aftermarket adapters may vary in thickness or material, which can cause blade wobble.
• Measurement check: The adapter’s inner bore is 25mm, outer diameter is typically 1-1/2”, and thickness is about 3/8”. Verify your blade’s center hole is large enough to sit over the adapter’s shoulder.

Key Things to Know

• Quality: Cast metal, holds up well under normal use. Won’t deform or crack like some plastic or cheap steel adapters.
• Installation difficulty: Easy—takes 5 minutes. Remove the old blade, slide the adapter onto the shaft (keyway aligns), then mount the blade and torque the bolt to 35–50 ft-lbs. No special tools needed.
• Common gotcha: If your blade is loose or wobbles after install, the adapter may not be fully seated on the shaft key. Double-check that the key is in place and the adapter is flush.
• Fitment note: Some newer MTD mowers use a 7/8” shaft—this adapter will not work. Always measure before ordering.

Should You Buy It

Buy this if you have an MTD-family mower with a confirmed 25mm crankshaft and need to replace a worn or lost blade adapter. It’s a direct OEM replacement that ensures a secure, wobble-free blade fit. If your mower uses a different shaft size, or you’re on a budget and can tolerate slight fit variances, consider an aftermarket alternative—but for reliability, this is the safe pick.