How do I determine which Ford ignition lock set to order using this diagram?

Measure the cut depth at the Number 6 tumbler station on the customer's key (16.85mm from the reference point). Match the measurement to a letter: 5.35mm = A, 4.70mm = B, 4.05mm = C, 3.40mm = D, 2.75mm = E, then order the lock set with that letter suffix.

What are the ignition lock set part numbers for Thunderbird/Cougar?

E6SZ-11582-A, E6SZ-11582-B, E6SZ-11582-C, E6SZ-11582-D, and E6SZ-11582-E, chosen by the letter code measured from the key.

What are the ignition lock set part numbers for Lincoln Town Car and Aerostar?

E6VZ-11582-A, E6VZ-11582-B, E6VZ-11582-C, E6VZ-11582-D, and E6VZ-11582-E.

How many tumbler stations does this key system have?

Ten tumbler stations, numbered 1 through 10, with station 6 used for the depth measurement.

What cut depth corresponds to code C?

A measured depth of 4.05mm at the Number 6 tumbler station corresponds to letter C.

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Ford 10-Cut Lock Cylinder & Key Diagram - Ignition Lock Set Part Numbers

10-cut lock cylinder and key dimensioned cut chart with tumbler stations and depths

TSB 87-24-2 General Door & Ignition Lock Service Tips
Publication date: 12/04/87

FORD: 1987-88 ESCORT/EXP, TEMPO, MUSTANG, TAURUS, THUNDERBIRD, CROWN VICTORIA
LINCOLN-MERCURY: 1987 LYNX, 1987-88 TOPAZ, SABLE, COUGAR, GRAND MARQUIS, MARK VII, CONTINENTAL, LINCOLN TOWN CAR
LIGHT TRUCK: 1987-88 AEROSTAR, RANGER, BRONCO II, E-SERIES, F-SERIES, BRONCO

ISSUE: Two types of key systems are used on Ford vehicles. The five (5) bit key system uses one (1) key to operate the ignition lock and a second to operate the outside door locks. The ten (10) bit key system uses one (1) key to operate the ignition lock and the outside door locks. The ten (10) bit key system services the ignition lock as a separate service part so the door locks would not have to be replaced in the event of an ignition lock failure.

ACTION: If service is required for the five (5) bit key system, the ignition and door locks are serviced separately. Refer to the appropriate Shop Manual for removal and installation procedures. If service is required for the ten (10) bit key system, a ten (10) bit ignition lock with partially cut keys is available. Refer to the following service procedure.

NOTE: Customers concerned with the heads of the new ten (10) bit ignition service keys not matching the original keys may be resolved by ordering blank keys from Rotunda. Cut the two (2) blank keys ordered from Rotunda on tumbler station numbers 1, 2, 3, 4, and 6 to match the new ten (10) bit ignition service keys supplied with the new service ignition lock.

1. Remove the ignition lock cylinder. Refer to the appropriate Shop Manual.
2. Using the Ford Rotunda key code cutting package, tool number 011-00003, measure the depth of the cut on the number six (6) tumbler station of the original key. Use this measurement to determine the correct service ignition lock set. Refer to the chart.
3. Using the original ignition key, decode tumbler station numbers 5, 7, 8, 9, and 10.
4. Cut the new service key on tumbler station numbers 5, 7, 8, 9, and 10.
5. Check the operation of the new service key in the new ignition lock and outside door locks.
6. Install the new service ignition lock.

NOTE: Retain both the original and new service key tabs for future key code identification.
OTHER APPLICABLE ARTICLES: 86-23-4

See also:
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Owner caption November 2025 · Photo 0 of 5000

This document is a technical reference diagram for the Ford 10-cut lock cylinder and ignition key system. It shows a side-profile drawing of an ignition key (the customer's key) with its ten tumbler stations numbered 1 through 10, and instructs the reader to measure the cut depth at the Number 6 tumbler station, located 16.85mm from the tip of the key. The measured depth corresponds to a letter code: 5.35mm = A, 4.70mm = B, 4.05mm = C, 3.40mm = D, and 2.75mm = E. That letter is then used to order the correct replacement ignition lock set. Two lock set part number tables are provided: for Thunderbird/Cougar, the ignition lock sets are E6SZ-11582-A through E6SZ-11582-E; for Lincoln Town Car and Aerostar, they are E6VZ-11582-A through E6VZ-11582-E. The diagram allows a locksmith or technician to identify and order the proper coded ignition lock cylinder set from a customer's existing key without disassembling the lock. The document also labels the measurement points and the direction of the tumbler stations on the key blade.

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Frequently asked questions

How do I determine which Ford ignition lock set to order using this diagram?: Measure the cut depth at the Number 6 tumbler station on the customer's key (16.85mm from the reference point). Match the measurement to a letter: 5.35mm = A, 4.70mm = B, 4.05mm = C, 3.40mm = D, 2.75mm = E, then order the lock set with that letter suffix.
What are the ignition lock set part numbers for Thunderbird/Cougar?: E6SZ-11582-A, E6SZ-11582-B, E6SZ-11582-C, E6SZ-11582-D, and E6SZ-11582-E, chosen by the letter code measured from the key.
What are the ignition lock set part numbers for Lincoln Town Car and Aerostar?: E6VZ-11582-A, E6VZ-11582-B, E6VZ-11582-C, E6VZ-11582-D, and E6VZ-11582-E.
How many tumbler stations does this key system have?: Ten tumbler stations, numbered 1 through 10, with station 6 used for the depth measurement.
What cut depth corresponds to code C?: A measured depth of 4.05mm at the Number 6 tumbler station corresponds to letter C.