Yes — replacing a cam lock on a cabinet or letterbox is one of the more approachable DIY locksmith tasks a homeowner can take on. There's no restricted licensing required for this type of work, and with the right replacement lock and a couple of basic tools, most people can complete the job in under 30 minutes.
What Is a Cam Lock?
A cam lock is a simple fastening device used on filing cabinets, tool cabinets, letterboxes, display cases, and similar furniture. It consists of a cylindrical barrel that fits through a pre-drilled hole, a cam (a flat metal tail) that rotates when you turn the key, and a retaining nut that holds the barrel in place from the back. When the key is turned, the cam swings to lock or release the door or panel.
Tools and Materials You'll Need
- Replacement cam lock (correct diameter and barrel length — see sizing below)
- Flathead or Phillips screwdriver
- Adjustable spanner or open-ended wrench
- Ruler or vernier callipers
- Pen or marker
You won't need any power tools for a standard cam lock swap.
Getting the Right Replacement Lock
Before buying anything, measure your existing lock carefully:
| Measurement | What to Check |
|---|---|
| Barrel diameter | Most common NZ sizes are 16 mm, 19 mm, and 22 mm |
| Barrel length (depth) | Must suit the thickness of your panel or door |
| Cam length and style | Match the existing cam shape (straight, offset, L-shaped) |
| Keying | Decide if you want a new key or a lock keyed alike to others |
Replacement cam locks are widely available at Bunnings and Mitre 10, as well as trade suppliers and locksmiths. As a rough guide, a basic cam lock typically costs anywhere from around $5 to $30 depending on quality and keying options — though prices vary, so check current stock.
Tip: If you're replacing multiple locks on the same cabinet and want them all to open with one key, ask for locks that are keyed alike. A local locksmith can also rekey locks for you if needed.
Step-by-Step: How to Replace a Cam Lock
1. Remove the Old Lock
- Open the cabinet or letterbox door so you can access the back of the lock.
- Hold the barrel steady from the front and use a spanner to unscrew the retaining nut from the back.
- Slide the old lock out from the front of the panel.
- Note how the cam is attached — usually a small screw or clip holds it to the barrel.
2. Prepare the Hole
- Check the hole is clean and free of debris.
- If the new lock has a slightly different diameter, you may need to enlarge the hole slightly with a step drill bit — but in most cases a like-for-like replacement will drop straight in.
3. Fit the New Lock
- Insert the new barrel through the hole from the front.
- Attach the cam to the back of the barrel (usually a single screw).
- Thread on the retaining nut from the back and tighten firmly with your spanner — don't overtighten on thin sheet metal or plastic panels.
- Test the key action before closing everything up.
4. Check the Cam Alignment
- Close the door and test the lock in both the locked and unlocked positions.
- If the cam doesn't engage the strike or latch properly, loosen the retaining nut slightly, rotate the barrel to adjust the cam position, and re-tighten.
NZ-Specific Considerations
Cam locks on residential letterboxes are not covered by the NZ Building Code in terms of licensing — this is purely a DIY-friendly task. However, if your letterbox is part of a body corporate or rental property, check with your property manager or landlord before making changes. Tenants in rental properties should refer to Tenancy Services for guidance on what alterations are permitted.
For outdoor letterboxes, choose a cam lock rated for exterior use — look for stainless steel or zinc alloy construction to resist NZ's coastal salt air and UV exposure.
Safety Note
Cam lock replacement carries minimal safety risk. That said, always:
- Make sure the cabinet is stable and won't tip while you're working on it.
- Keep small parts (nuts, cams, screws) away from children.
- If the cabinet contains electrical components (e.g., a switchboard enclosure), do not attempt any work near wiring — contact a licensed electrician registered with the Electrical Workers Registration Board (EWRB).
When to Call a Professional
While cam lock replacement is DIY-friendly, call a qualified locksmith if:
- The lock barrel is seized, broken, or the key has snapped inside it.
- You need a master-keyed system across multiple locks.
- The cabinet is a high-security or fire-rated enclosure where the original hardware specification matters.
- You're unsure of the correct replacement part and don't want to risk damaging the panel.
A professional locksmith can also supply and fit the correct lock in one visit, saving you a trip to the hardware store. You can find qualified local locksmiths on tradedirectory.co.nz.
