How to Rebuild an Oversized Keyway

 In Belzona Educates, How To Series


Oversized keyways

Oversized keyway is a common problem when it comes to the functionality of rotating equipment. Small components always lead to large problems. Keys in shafts have to withstand the stress of sudden starts and stops. Whether it wears or breaks, the entire unit is shut down. In many plants, the costly and time-consuming process of replacing the key still involves disassembly of the machine, removal of the shaft and the machining of a new key and keyway. While this process has significant costs, it is usually only a fraction of the cost of the unit being out of service until it is complete. Maintenance management tired of the inconvenience and the expense of traditional methods have adopted Belzona solutions. By using a Belzona metallic polymer, a damaged keyway can be rebuilt in situ, eliminating the need for time-consuming and costly disassembly. Since Belzona polymers are 100% solids, there is no dimensional change from application to full cure. This means that the key can be used to construct a new keyway with a perfect fit.

Belzona solution

In this blog post, we demonstrate how to repair an oversized keyway with Belzona 1111 (Super Metal), an epoxy based metal repair composite. You will learn how to carry out a keyway repair in situ, without the need to disassemble the equipment or take the shaft out of service. Belzona metal repair composites eliminate the need for welding or any other type of hot work, thus providing a safe environment for personnel.

Oversized keyway repair drawing

Oversized keyway repair drawing

Belzona How-To

To carry out an oversized keyway repair, we used Belzona 1111 (Super Metal), a new key, Belzona 9111 (Cleaner/Degreaser), Belzona 9411 (Release Agent) and a few tools from our machine shop. First, we had to condition the key with Belzona 9411. Then, we filed down the internal surface of the keyway to remove all sharp edges and protrusions, and roughened the surface to achieve maximum adhesion with the epoxy product. The surface was cleaned with Belzona 9111 to remove all the contaminants. Next, Belzona 1111 was thoroughly mixed and applied to the internal surface of the keyway until the keyway was filled with the mixed product. The key was carefully positioned on top of the applied product and pressed down firmly to allow the excess product to exude. Once the product fully cured, the key was removed from the keyway.

To learn more about Belzona solutions for the mechanical power transmission equipment, visit:

Supplies and tools needed for an oversized keyway repair with Belzona 1111

Step-by-Step Instructions of an Oversized Keyway Repair with Belzona 1111

Keyway Repair
Step 1: Condition all sides of the key with Belzona 9411 (Release Agent).

Keyway repair
Step 2: Prepare the surface using a file to remove sharp edges and protrusions.

Keyway repair
Step 4: Clean and degrease the keyway to remove all surface contaminants.

Oversized keyway repair
Step 5: Tape the repair area.

Oversized keyway repair
Step 7: Apply the mixed material directly onto the prepared surface of the keyway, pressing down firmly to ensure maximum contact with the surface.

Oversized keyway repair
Step 8: Fill in the keyway with the mixed product.

Oversized keyway repair
Step 9: Remove excess product.

Oversized keyway repair
Step 10: Position the key over the applied product and press down firmly to allow the excess product to exude.

Oversized keyway repair
Step 11: Remove tape.

Oversized keyway repair
Step 12: Release key.

Oversized keyway repair
Step 13: Smooth out the surface with an emery cloth.

Oversized keyway repaired
Complete application

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