How to Replace a Doorknob and Deadlock

By Mick — handyman, Newcastle NSW.

Easiest small job in the trade, supposedly. Punter walks into Bunnings, grabs a Lockwood Cosmo or a Brava deadlock, takes it home, opens the box at 4pm on a Saturday, and discovers their new lock has a 60 mm backset and the door is set up for 70 mm. Or vice versa. Cue an angry call to me on Sunday morning.

Backset — the distance from the edge of the door to the centre of the bored hole — is the one measurement that catches out 90% of DIY doorknob and deadlock swaps in Aussie homes. Australian doors are a mix of 60 mm and 70 mm backsets, sometimes within the same house. Older doors (pre-1980s) are usually 60 mm. Newer doors are mostly 70 mm. Some commercial-grade and security doors are 89 mm. Get it wrong and the lock either won’t fit or the bolt won’t engage the strike plate.

The other gotcha — and this is the insurance one — is that AS 5039 deadlock standard is the spec your home contents insurer expects on entry doors. A generic Bunnings deadlock might not be AS 5039 compliant, and if you get burgled and the assessor sees the lock, your claim can get reduced or denied. Here’s how I do a doorknob and deadlock swap that ticks all the boxes.

What you’ll need

• The new lock — for entry doors, AS 5039 compliant deadlock (Lockwood 001, Brava Urban DX, Whitco Tasman MK2)
• Phillips screwdriver, flathead screwdriver
• Tape measure
• Cordless drill
• 25 mm and 54 mm hole saws (for upsizing if backset is wrong)
• Wood chisel 25 mm and a hammer (for the strike plate)
• Pencil, masking tape
• Sandpaper 180 grit
• The existing lock’s strike plate as a template

Step 1: Measure the backset BEFORE you buy the lock

Don’t go to Bunnings first. Measure first. With the door open, measure from the door edge to the centre of the existing bored hole on the face of the door. That’s your backset. It’ll be 60 mm or 70 mm.

While you’re there, measure the bore hole diameter (usually 54 mm) and the latch hole on the door edge (usually 25 mm). And measure the existing strike plate cutout on the door jamb — note its position and depth.

Then go shopping. Most Aussie locks come with adjustable backset (60/70) — Lockwood and Whitco do — but cheaper Bunnings imports are fixed. Read the box.

Step 2: Confirm AS 5039 compliance for entry doors

For front, back, and any external door — including the laundry door that opens to the carport — the deadlock must be AS 5039 compliant. Look on the box for the AS 5039 mark or the words “5-pin Australian Standard.” Lockwood 001, Brava Urban DX, Whitco Tasman MK2, and the Yale Curve all comply. Anything sold as a “knob lock” or “passage lock” alone is not enough on an entry door.

Bonus: AS 5039 means a 5-pin cylinder (not the cheap 3-pin), and a hardened-steel deadbolt that resists a hammer strike. It’s the bare-minimum standard your insurer assumes is fitted.

Step 3: Remove the existing lock

From the inside face, undo the two screws on the rose. The rose pulls off, exposing the spindle. The outside knob and inside knob then separate. From the door edge, undo the latch faceplate screws (usually two phillips) and slide the latch out.

For a deadlock, the cylinder undoes from the inside; usually one set screw on the inside cover, then the cylinder threads out. Don’t lose the springs — there’s usually a small return spring inside that wants to escape.

Step 4: Inspect the door for damage

Old doors get worn around the latch. If the latch hole has chipped out timber or the bore has cracks, fill with epoxy wood filler (Selleys Knead-It Wood) before fitting the new lock. New lock into a chewed-out hole = the lock will work loose in 6 months.

Step 5: Dry-fit the new lock to check the backset

Before driving any screws, hold the new latch up to the bore hole. The latch tongue should sit centred in the bore. If it sits skewed (latch face on the door edge but the bore hole 10 mm off), you’ve got a backset mismatch and you need to either:

• Adjust the latch’s backset (most Lockwood and Whitco latches have a slide-out adjuster)
• Or, return the lock and buy the right one

Don’t try to “make it work” by drilling a new bore. The cosmetic mess is permanent.

Step 6: Fit the latch first, faceplate flush

Slide the latch into the door edge. The faceplate sits in a recess (mortice). On most Aussie doors, the recess is 3 mm deep and the faceplate sits flush with the door edge. If the new faceplate is bigger than the old, you need to chisel the recess slightly larger — masking tape around the edges, mark the new boundary, chisel out 1 mm at a time.

Secure the faceplate with the supplied screws. Don’t over-tighten — you’ll strip the soft pine timber inside the latch hole.

Step 7: Fit the knob/lever assembly through the bore

From the outside, push the spindle through the bore so it engages the latch. From the inside, slide the inside knob onto the spindle. The two knobs join via two long screws that pull the roses together. Tighten gradually, alternating, until the knobs sit firm against the door without binding the latch.

Test the action: turn the knob. The latch should retract smoothly. If it sticks, the knobs are over-tightened — back the screws off a quarter turn each.

Step 8: Fit the deadlock above the knob

Aussie convention is the deadlock 150 mm above the knob, centred on the bore line. If you’re swapping a deadlock for a deadlock, the holes are already there. If you’re adding a deadlock to a door that didn’t have one, that’s a hole-saw and chisel job — masking tape both sides of the door, mark the centre on both faces with a small drill bit going from one side, then hole-saw from each side meeting in the middle (drilling through from one side splinters the exit face badly).

Cylinder out, throw the bolt to test, cylinder back in.

Step 9: Adjust the strike plate on the jamb

Close the door slowly and watch where the latch tongue contacts the jamb. Mark with pencil. The strike plate cutout should align with that mark. If it doesn’t:

• 2 mm out: file the strike plate hole bigger
• 5 mm or more out: you need to plug the old cutout (timber filler or a glued-in plug) and chisel a new cutout in the right place

The deadbolt strike needs a deep cutout — 25 mm minimum. A shallow strike means the deadbolt only half-engages and a forced-entry attack pops the door.

Step 10: Test 50 times before you call it done

Lock and unlock from inside. Lock and unlock from outside with the key. Throw the deadbolt with the door open, then close — does the bolt enter the strike cleanly? Slam the door (gently) — does the latch catch? Try the key from outside while the door is closed and locked. Hand the key to a household member and have them try.

I do this 50 times. If anything sticks or hesitates even once, something’s not right. Find it now, not at 11pm when you’re locked out.

Step 11: Cut spare keys at install time

Most Aussie deadlocks ship with two keys. Take both to a Bunnings or a Mister Minit and cut at least two spares immediately — one for an emergency hide spot or a trusted neighbour, one for a tradie key safe. Keys cut from a fresh original cut perfectly; keys cut from a worn second-generation key cut sloppy and start jamming the lock.

Also: register the key code (printed on the key itself or on the lock packaging) somewhere safe. With the code, a locksmith can cut a new key without the original. Without it, they have to pick or drill the lock.

Step 12: Lubricate the cylinder once a year

Aussie front doors get sun, dust and salt air. The pin tumbler cylinder needs a graphite-based lubricant once a year — DO NOT use WD-40, oil-based lubricants attract dust and gum the cylinder up over months. INOX MX2 dry-film or proper graphite lock lube (Lockwood-branded available at Bunnings). One puff into the keyway, work the key in and out a few times. Cylinder lasts 20 years.

The Mick rule

The Mick rule for doorknobs and deadlocks is: measure the backset, buy AS 5039, test 50 times. Backset gets you to a lock that physically fits. AS 5039 keeps your insurance valid. Fifty tests find the binding before it strands you. Skip any of those and the cheap lock you bought for $89 ends up costing you a $400 locksmith call-out and possibly a denied insurance claim.

Got a lock swap with a wrinkle? Send us a write-up.