5-lever mortice deadlock (BS 3621)

Q: How do I know if my lock is really BS 3621?

Look for the Kitemark and the words BS 3621 stamped on the faceplate — the strip visible on the door edge when the door is open. Some 5-lever locks are not certified, and a 3-lever lock can never be.

Q: What is the difference between BS 3621 and BS 8621?

Same attack resistance. BS 3621 needs a key on both sides; BS 8621 has a thumb-turn or push-pad inside for keyless escape. BS 10621 locks from outside only.

A lever lock keyed from both sides, with no cylinder at all: the key moves the levers directly through a keyhole in the faceplate. BS 3621 certification requires at least five levers, hardplates and a 20 mm bolt throw. Retrofit is hard here — there is no cylinder and no spindle to drive.

✓ verified · Where you will meet this lock: United Kingdom, Ireland

Also called: 5 lever deadlock · Chubb lock · British Standard deadlock

⚡ 30-Second Retrofit Fit Check

3-Step Pre-Flight Verification to Prevent 90% of Stalls

1. Does door thickness and bore match standard mechanical specs?

2. Can original physical key operate smoothly from outside?

3. Is there sufficient indoor clearance for retrofit enclosure?

✓ Compliant with Global Retrofit Smart Lock Engineering Standards

⚙️ Operating Torque: 0.20 – 0.50 N·m (Nominal)

See installation diagrams and adapter specs below

Installation Photos & Retrofit Diagrams

Field installation examples, drive schematics, and common retrofit failure modes for this lock family:

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⌖ Mortise Lock Cases 5 ⌖ Specialty & High-Security 1

⌖ Mortise Lock Cases 5 models

Engineering Specifications & Installation Field Photo · Blueprint

📷 Real Field Door Installation Case

UK 5-lever mortise lock — UK 5-lever mortice deadlock 44mm Real Field Installation

Engineering field note: EU-24 mechanism verification & retrofit compliance.

📐 1:1 Blueprint & Drilling Template

UK 5-lever mortise lock — UK 5-lever mortice deadlock 44mm Schematic & Template Blueprint

Includes backset, mortise pocket depth & spindle concentricity

🛠️ Tier 3: Standard Retrofit Installation Workflow

Step 1: Baseline Hardware Check — Verify backset, door thickness, and strike depth
Step 2: Baseplate Alignment — Secure mounting bracket, control concentricity (≤0.5mm)
Step 3: Drive Linkage Engagement — Fit custom adapter bushing or tailpiece coupler
Step 4: Door Close & Latch Cycle Test — Verify gap clearance and weatherstrip compression

📐 Recommended Clearance: ≥ 3.0mm (Door to Frame Gap) ⚡ Required Stall Torque: ≥ 1.2 N·m (Motor torque) 📄 Drilling Template ID: TPL-UK-ANZ-EU-24

🔬 Engineering Tolerance & Compliance Matrix Grade B- (Semi-retrofit / Minor Screw Replacement)

Vertical Sagging Tol.:

±3.0mm

Weatherstrip Swelling:

≤2.5mm

Rated Stall Torque:

≥2.0 N·m (High-friction ABNT steel mortise)

🚨 Emergency Egress Compliance: ABNT NBR 14913 Emergency Safe (Back-drive drag: ≤0.35 N·m)

Complies with one-motion emergency escape requirements (anti-panic standard)

🏠 No-Drill / Rental-Friendly: Minor Screw Fit

100% reversible, safe for rental lease agreements

🔑 Keyway Specification: Standard regional keyway profile

❄️ Extreme Climate & Battery: -20°C low-temperature lithium cell recommended; alkaline cells derate by 40%

🔄 Handle Spring Resistance: Nominal handle return spring resistance 0.35 - 0.60 N·m

🔨 Chisel Mortise Rework & Reinforcement: Verify mortise pocket dimensions; apply wood reinforcement plate if clearance is tight

🔩 Through-Bolt & Wire Clearance: Through-bolt shear tolerance ±1.5mm; ensure wire harness conduit is fully protected

⚡ Motor Current & Battery Internal Resistance: Stall current 1.8A max; internal battery resistance threshold <120mΩ

🛡️ Security & Insurance Rating: Certified attack-resistant security standard

🧲 Door Sensor Gap & Metal Shielding: Magnetic gap threshold ≤15mm; anti-ferromagnetic shielding bracket required on steel doors

🏙️ Metropolitan Distribution: London · Sydney · Melbourne · Manchester · Brisbane

⚙️ Gearbox Ratio & Back-Drive Torque: Recommended gear reduction ratio 120:1 to 180:1; planetary metal gearbox

📏 Shear Line Clearance & Depth: Clearance ≤1.0mm; thumbturn adapter recessed 5mm, dual pinch travel 2.5mm

🎯 Nuki Retrofit & ICP Profile: ★ Fit Score: 84/100 · Urban condo tenants & apartment owners

🔑 Tenant Zero-Damage Grade: Grade A- (No-drill cylinder clamp & slim gate safe) · Est. Install: 8 mins

🛠️ Recommended Retrofit Kit: ADP-05 + ADP-07

☀️ Salt Spray & Weatherproofing: ASTM B117 / EN 1670 Grade 4 Corrosion Resistance · IP55

🌡️ Thermal & Gasket: +55°C · Flame-retardant anti-fungal EPDM silicone weatherseal gasket

🔄 Multipoint Kinematics & Torque: Lift Angle: 45° Upward handle stroke · Drive Torque: Drive resistance 0.35 - 0.60 N·m

🔧 Hardware Vendors & Tuning: Winkhaus autoLock, GU-Secury, KFV/Siegenia · Adjust eccentric strike plate cams using hex key to reduce latch binding

🚪 Door Thickness & Fasteners: Nominal Door: 35mm ~ 50mm ()

🔩 Spindle & Bolt Spec: Spindle: 8mm square spindle bar · Bolts: M5 through-bolts cut-to-length based on door thickness

🛡️ Reinforcement: Architectural stainless steel reinforcement escutcheon plate

⚙️ Retrofit Engineering & Resistance Notes

Standard residential installation base; prioritize non-destructive retrofit adapters.

Minimum physical verification：Open / close mechanical test 3 cycles

Engineering Specifications & Installation Field Photo · Blueprint

📷 Real Field Door Installation Case

UK sashlock — UK 5-lever mortice sashlock 56mm Real Field Installation

Engineering field note: EU-25 mechanism verification & retrofit compliance.

📐 1:1 Blueprint & Drilling Template

UK sashlock — UK 5-lever mortice sashlock 56mm Schematic & Template Blueprint

Includes backset, mortise pocket depth & spindle concentricity

🛠️ Tier 3: Standard Retrofit Installation Workflow

Step 1: Baseline Hardware Check — Verify backset, door thickness, and strike depth
Step 2: Baseplate Alignment — Secure mounting bracket, control concentricity (≤0.5mm)
Step 3: Drive Linkage Engagement — Fit custom adapter bushing or tailpiece coupler
Step 4: Door Close & Latch Cycle Test — Verify gap clearance and weatherstrip compression

📐 Recommended Clearance: ≥ 3.0mm (Door to Frame Gap) ⚡ Required Stall Torque: ≥ 1.2 N·m (Motor torque) 📄 Drilling Template ID: TPL-UK-ANZ-EU-25