How to Replace the Lock Pin O-Ring on a Makita Grinder

Spindle lock leaking? It's time to face the fix. Whether you are a master mechanic or a garage-based grinder, eReplacementParts.com provides the parts, procedures and facts you need to fearlessly fix what fails you.

The spindle lock O-ring is part of the lock button assembly on your grinder. Its purpose is to seal the opening where the shoulder pin passes through the gear housing. If the O-ring fails, you’ll likely begin to notice small amounts of oil leaking from the lock button assembly.

This article provides step-by-step instructions for removing and installing the spindle lock O-ring on a Makita grinder.

Let's get started.   REMOVING THE O-RING [top] 1. Remove the side handle.

Unscrew and remove the side handle from the grinder.

  2. Remove the guard.

Loosen the lock-screw on the guard assembly.

Rotate the guard assembly to disengage it from the housing.

Remove the guard from the grinder.

  3. Remove the gear housing.

Remove the (4) screws from the gear housing.

Separate the gear housing from the motor housing.

  4. Remove the bearing box from the gear housing.

Remove the (4) screws from the bearing box.

Separate the bearing box from the gear housing.

  5. Remove the lock button assembly.

Use a small screwdriver to (pry) disengage the pin cap from the top of the shoulder pin.

Remove the pin cap from the gear housing.

Remove the compression spring from the gear housing.

Remove the shoulder pin from the gear housing.

    6. Remove the O-ring from the shoulder pin.

Slide the O-ring off the shoulder pin.

  INSTALLING THE NEW O-RING [top] 7. Install the O-ring.

Slide the new O-ring onto the shoulder pin.

  REASSEMBLING THE UNIT [top] 8. Reinstall the shoulder pin.

Install the shoulder pin into the gear housing.

The rounded portion of the shoulder pin should pass through the housing and remain exposed on the top of the housing (it will attach to the plastic button in later steps).

      9. Reinstall the bearing box onto the gear housing.

Install the bearing box onto the new gear housing.

Secure the bearing box with the (4) screws.

  10. Reinstall the lock button assembly.

Install the lock-pin compression spring onto the exposed portion of the shoulder pin.

Install the pin cap (plastic button) onto the shoulder pin.

Secure the pin cap to the shoulder pin using adjustable pliers.

  11. Reinstall the gear housing.

Install the gear housing onto the grinder (aligning the mounting holes with the gear housing cover and the motor housing).

Secure the gear housing to the grinder with the (4) screws.

      12. Reinstall the guard.

Install the guard assembly onto the grinder.

Rotate the guard assembly to engage the mounting plate.

Secure the guard with the (1) screw.

  13. Reinstall the side handle.

Install the side handle onto the grinder.

Tighten the side handle until secure.

You can't place a value on a job well done, unless you did it yourself. (Which you did.) Now you can place that value back into your own pocket. (Or into your business.) Not only did you refine your grinder at a fraction of the cost of replacement; you have expanded your skills far beyond the daily grind.

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