Hi, there! Thank you for your query about the Makita PC5001C concrete planer. To replace a worn diamond wheel, begin by pressing the shaft lock to hold the shaft in place. Then, use the provided lock nut wrench to loosen the lock nut by turning it counterclockwise. Once the lock nut is loosened, remove the old diamond wheel. To install a new one, simply follow the removal steps in reverse. When securing the new diamond wheel, be sure to tighten the lock nut firmly to ensure proper installation. For more details, please see page 7 of the user manual. When you’re ready to purchase, simply click "Add to Cart," complete the required fields, and we’ll handle the rest. Thank you for choosing PlumbersStock. Have a wonderful day!