Acknowledgments

Summary

Introduction

Briggs & Stratton (B&S), the lock division of which has since become Strattec (www.strattec.com), has been the primary supplier of locks (and key blanks for these locks) to General Motors essentially since the beginnings of GM. Briggs & Stratton was formed early in the 20th century by two former students of North Dakota State University, Steve Briggs and Harold Stratton. Together the two men started a business supplying parts to the relatively new automotive/truck industry. At one time they bought a motorized AO Smith buckboard, and from this developed and built two Briggs & Stratton automobiles.

Automotive design and assembly proved to be a temporary diversion. Briggs and Stratton decided to supply the industry rather than compete in it, and focused on developing, manufacturing, and supplying automotive hardware. From handles, hinges, and latches, B&S branched out into locks and keys, and to support these, developed high-volume die-casting technology and related processes. (This same experience and technology was later applied to the now better-known small-engine business.) B&S quickly became the exclusive supplier of GM locking systems. However, a particularly difficult labor strike at B&S in the late 1940s created costly disruptions at GM assembly plants. To minimize the impact of a recurrence, GM obtained a licensing agreement from B&S to allow Rochester Products, better known as the fuel delivery systems branch of GM, to build B&S locking systems as a second source.

B&S Lock Manufacturing

Keys were manufactured separately from the locks, in advance. The blanks were stamped, their grooves milled, the lettering on the key bow coined, and the key bittings cut per code in a punching operation. The keys were stored in bulk by letter designation and code, and then added to the locksets prior to packaging. Basic locksmith terminology of the physical features of keys is illustrated in the schematic below:

Basic Key Terminology

GM Keying Systems

The new B&S keying system used a series of eight key blanks, each with a different blade cross-sectional geometry (key section) and a particular key part number and groove type, but also more simply designated by the letters A, B, C, D, E, H, J, and K. The short designation caused the keys in this system to be commonly called the "letter keys". In addition to increasing the number of key sections, the new system added a fifth key cut depth, and so increased the number of key combinations possible on a given key blank by approximately 25% from the earlier system. Both features improved security by making it a little more difficult to interchange keys.

As shipped from the GM assembly plant, vehicle keys had a knockout area at the key ring hole that was imprinted with a 4-character code (number/letter/number/number) that correlates to the lock tumbler combination (a 6-digit number described in more detail below). (Only the original keys, and B&S pre-punched factory replacement keys, come stamped with the lock code.) The knockout tabs were made to be removed and stored by the owner in case the keys were lost (so that a locksmith could make a new key from the code number without having to remove a lock). There was a small hole in the knockout area to accommodate a temporary wire key ring. If the knockouts were left in the key, the tiny hole through the knock-out was often drilled-out or reamed to a larger diameter to allow a key ring to pass through the hole. Until about 1980, B&S furnished GM key blanks only with the knockouts intact. Locksmith Dorothy Friend wryly suggests that this must have been "to give the locksmith something to do during slack periods, since most of us needed the knockouts punched out to get them on the hooks of our key boards." The knockouts for the key blanks, obviously, did not have a code stamped on them.

The 1967-68 years were a transition period that saw the earlier-style (1935-66) key bows (the "bow", in locksmith terms, is the head of the key that is used as a grip or handle) retained on the new letter-key blades. Several key examples are illustrated below. The first set shows a 1936 GM secondary key with the knockout intact (but the knockout hole drilled-out to a larger size). Note that the GM and B&S logos are on the opposite sides from later years, as well as the use of the pre-WWII "BASCO" logo (for Briggs And Stratton COrp) and the all-numeric keycode. The 1967 A/B example shows a primary (ignition/door) key from a Briggs & Stratton lockset, while the secondary key is from a Rochester Products lockset. Like the 1936 example, the 1967 set has the knockout wire ring hole drilled out. Also note the relative similarity between the Groove 15 key section and the Groove 50 (A) key section - the difference being that the A key has a wider upper groove. In the 1968 C/D example with the knockouts removed, note that the primary, or ignition/door key, is from a Rochester Products lockset, while the secondary key is from a Briggs & Stratton lockset. The 1969 example, also with the knockouts removed, shows the new key bow shapes - the rectangular and oval forms still in use today, aka, the "Corporate" keys. Note in the 1969 example (the key cuts have been masked at the request of the donor of the images) that there are no distinguishing features of the lockset manufacturer on the Corporate keys.

1936 GM Groove 15 Key
(click on an image to expand)

		Secondary Side 1	Secondary Side 2

1967 GM A/B Keys
(click on an image to expand)

Primary Side 1	Primary Side 2	Secondary Side 1	Secondary Side 2

1968 GM C/D Keys
(click on an image to expand)

Primary Side 1	Primary Side 2	Secondary Side 1	Secondary Side 2

1969 GM E/H Keys
(click on an image to expand)

Primary Side 1	Primary Side 2	Secondary Side 1	Secondary Side 2

To bring us to completely modern times, while GM has since introduced new design locking systems, it has continued to use the letter key system on other models. The first VATS (Vehicle Anti-Theft System) ignition locks were used on the 1986 Corvette. This system used one of the letter key sections, but added a resistor pellet embedded in the neck of the primary key. The primary key also required a longer neck to allow the resistor pellet contacts to reach into the ignition lock. The first year for Camaro to have a VATS ignition was 1989. Other neck length and bow shape changes occurred on other models in subsequent years, but the letter keyways continued to be used.

In 1992 Skylark and Cavalier got a new primary keyway - the first keyway change on a domestic vehicle line since 1967. (Imported vehicles like Alliant (87), Nova (86), Sprint (84) and Luv (81) had different keying systems.) Other new keyways have since been introduced, as well as double-bitted keys (keys with cuts on both sides).

Examples of GM key types (but not all possible bow/groove types) are shown graphically in the excerpt below from a mid-1980s B&S document. Note the groove number/letter shown to the left of each key blank, and the cross-section shape shown to the right of each key blank.

GM Key Types
(click on image to expand)

The "Letter Keys" - Key Blank Design and Key Cuts

The different designations for the key blanks reflect differences (in geometry and location) in the milled grooves that run down the length of the key. Four pairs of grooves in the new system instead of the single groove in the old system allowed additional combinations of keys, which provided additional security. For example, the key cuts can be identical on keys from two different pairs, say an A blank and a C blank, but they physically can't be inserted into the other lock because the milled grooves are in different locations. (Exceptions to this can occur in aging systems due to extensive wear on both the keys and locks that can allow worn keys of some letters to be inserted into worn locks of other letters. Additionally, there are some non-OEM replacement locks, including some by Strattec, that use a universal keyway and will take any of the B&S blanks, but these were never used on GM vehicles at the assembly plant.) The different milled grooves are shown in the side-by-side comparisons of the ABCDEHJK blanks in the previous illustration.

Starting in 1974, the primary key was changed to fit only the ignition and the secondary key was applied to the rest of the locks. As noted several times previously, the actual bow-shape of the 1967-68 letter key blanks differed from later years, with the primary keys having a bow shaped like an incomplete octagon (sometimes called the "hex" key) rather than a rectangle/square, and the secondary keys being tear-drop shaped rather than oval. These 1967-68 key bows were the same as those used in the previous key design from 1935-1966, but the key blades used the different letter key sections.

The letter-key designations are stamped on the keys. According to Len White, Chief of the B&S Automotive Locks Division, during the years when both Rochester and B&S supplied locking systems on identical key blanks (1969 and following), the stamps from the two suppliers were oriented in different directions. Rochester Products (it is believed) stamped their keys so that the letter was correctly oriented when the key is held with the blade horizontal to the ground. The stamp on (B&S) was correctly oriented when the blade was held perpendicular to the ground. CRG is still attempting to confirm this interpretation of the letter stamping orientations.

The lock type, letter designation, B&S blank number, B&S groove type and year of application for all GM keys from 1935 to the present (excepting modern non-letter key systems), are shown in the table below:

                              B&S**
Application* Designation Blank  Groove  Years***
------------ ----------- ------ ------- -------------------
Primary****  -              -     15    1935-1966

Primary      A           320296   50    1967
Secondary    B           320298   51

Primary      C           320368   54    1968
Secondary    D           320369   55

Primary      A           320588   50    1971 1975 1979
Secondary    B           320589   51    and 1983-1986

Primary      C           320652   54    1972 1976 1980 
Secondary    D           320653   55    1987-1990

Primary      E           320404   56    1969 1973 1977 1981
Secondary    H           320405   57    and some 1991-1999

Primary      J           320470   58    1970 1974 1978 1982
Secondary    K           320471   59    *****
------------------------
    *Through 1974, the Primary key was applied to the
     Ignition and Doors, while the Secondary was applied to
     the Trunk and Glovebox. Starting in 1975, the Primary
     key was used only in the Ignition, while the Secondary
     key was used in the Doors and Trunk.
   **Aftermarket manufacturers often use a different groove
     numbering system, such as the "EZ" system. For a given
     key blank, the EZ System groove numbers are different
     than the OEM B&S groove numbers for the same key
     blank.
  ***Dates are generally correct, but may vary for early and
     late models in a model year, or for fleet and law
     enforcement vehicles.
 ****Many models prior to 1967 used only one key with an
     octagonal key bow. If there was a secondary key, it
     used the same key blade with a different cut and a
     teardrop-shaped key bow.
*****Modern use of the J/K keyways is still uncertain
     and is being researched by CRG.

The process of cutting the factory key cuts, "key bitting," used a punching process rather than the more commonly used replacement key process of grinding, such as used in hardware store key duplicators. The factory machine was called, naturally, a "key bitting punch":

key bitting punch, n - a manually operated device which stamps or punches the cuts into the key blade, rather than grinding or milling them.
Source: http://www.locksoft.com/gloscopy.htm

The key cut appearance resulting from a factory key punch is somewhat simulated by several hard-to-find aftermarket key punch machines. However, you will have a difficult time distinguishing between the results from one of these punch machines and one of the better rotary grinding machines. The rotary cuts will have a slight arc (the cutters are around 2-1/2 inches in diameter) that is difficult to see on a short cut, and the angle of cut may (or may not) be as close as those produced by the punches. Punch machines include:

• A Curtis "clipper" - fairly popular with car dealers.
• B&S made a punch-type machine just for the groove 15 (4 tumbler-depth keys, 1935-1966). It operated simply by inserting the key blank, moving a lever to the appropriate position for the next cut, setting the depth number, and then hitting a little knob with a hammer - and repeating this for all six positions. Dorothy notes, "I think the B&S punch holds the key blank by gripping it in one of the grooves; if so, it would not be accurate for cutting the #1-4 depths on the lettered keyways."
• An "Exacta" key machine.

GM Key Codes

2000 key codes were assigned for each of the primary and secondary keys in a given year (some out-of-sequence exceptions to the normal selections have been documented). The actual tumbler numbers associated with the key-codes were semi-randomized, documented in tables, and will not be reproduced here. For the first-generation Camaro years, the 12,000 4-character key codes were generally taken from the following list:

               1967          1968          1969
           ------------  ------------  ------------
Primary    0V00 to 9V99  0N00 to 9N99  0J00 to 9J99
           0W00 to 9W99  0P00 to 9P99  0K00 to 9K99

Secondary  0X00 to 9X99  0R00 to 9R99  0L00 to 9L99
           0Y00 to 9Y99  0T00 to 9T99  0M00 to 9M99

These locks have 6 tumbler positions (except the glovebox, which fits a 6-position key but only uses 5 of them) and there are 5 possible cut depths for each tumbler. At most there are 5x5x5x5x5x5 combinations, or a total of 15,625 theoretical key cut combinations for each groove type. In actual practice there are far fewer practical combinations, since some combinations would never be used, such as the 5 combinations where all 6 tumblers are at the same height, and other tumbler combinations resulted in impossible key geometries, such as the many combinations where the 1 and 5 tumblers would have been in adjacent positions.

B&S Key Cuts

Each standard tumbler size cuts 0.025-inch more from the blade than the previous size: the #2 cut leaves a 0.225-inch high blade, #3 a 0.200-inch blade, #4 a 0.175-inch blade, and with a #5 cut 0.150 inch of the blade remains. So the root depth is the measurement from the back of the blade to the deepest point of the cut. (Note that the 1935-1966 B15 blade used the first four of these five cuts.)

Key Cut Geometry
(click on figure to expand)

The next critical dimension is the distance of each cut from the key blade shoulder, also known as the "bow stop". Each of the six tumbler positions is located at a specific nominal dimension from the blade stop as shown in the above Figure. The distance between each tumbler position is 0.092 inch, and this is the same distance that the middle of the key cuts must be from the adjacent tumbler.

By measuring the uncut depth of your key blade with an inexpensive caliper at each of the appropriate positions, you can reverse-engineer the tumbler depth numbers and determine the tumbler combination of your lock. From this, many locksmiths can do a reverse lookup in a table to arrive at the original factory code that was stamped on the locks and the key knockouts, and printed on broadcast sheets and vehicle assembly plant shipping summaries. When you perform the measurement, wear on the keys will make the cuts deeper (remember - this is actually the distance across the remaining uncut area), so you would generally adjust your measured value upward to the next standard tumbler depth. For example, if a cut measures 0.219 inch, you would adjust up to the #2 tumbler (0.225 inch), rather than down to #3 (0.200 inch). The convention for listing the cuts in the combination for these is from bow to tip - a key with a combination of 132445 would have more of the key blade cut away toward the tip than near the bow. An example of this is shown below:

           Measured   Original
  Tumbler  Remaining    Root    Tumbler
  or Cut     Depth     Depth     Depth
  Number    (inch)     (inch)    Number
  -------  ---------  --------  -------
     1      0.243      0.250       1
     2      0.198      0.200       3
     3      0.220      0.225       2
     4      0.173      0.175       4
     5      0.173      0.175       4
     6      0.148      0.150       5

The tumbler combination for this example
lock is therefore 132445, which corresponds
(found via a locksmith's look-up table)
to the 4-character letter code stamped
on the original key knockouts.

B&S Locks

Trunk Lock Exploded View

Door Lock Exploded View

The locks came with one of two types of tumblers: conventional disk tumblers, as typified by the glovebox lock, and sidebar disk tumblers, used on all remaining locks. In the case of the sidebar tumblers, activation by the proper key moved all the tumblers to a height that caused a notch in all the tumblers to line-up with a rib in the spring-loaded sidebar. The sidebar then moved inward a distance equal to the height of the rib, which freed the cylinder plug to rotate in the cylinder case. Sidebar tumblers are shown below:

Sidebar Lock Tumblers

With the conventional disk tumblers used in the glovebox, the tumblers themselves are the actual restriction that prevents the cylinder from turning. Activation by the proper key moves all the tumblers out of the way and the cylinder plug can then rotate inside the cylinder case. Conventional disk tumblers are shown below:

Conventional Disk Tumblers

The case caps (the bright-metal exterior trim) on door and trunk locks provide a good indicator as to whether the locks have been field serviced. Factory case caps are crimped on (nice and neatly) all the way around the circumference, holding the dust shutter, dust shutter springs, and cylinder plug in the case. A factory case cap is normally destroyed in removal, and replaced with a service-style case cap. It is possible to very carefully pry off a factory cap, and painstakingly restake it; however, if this has been done, the work will be fairly noticeable on the backside of the case where the cap was restaked. Replacement case caps differ from factory cases, having 4 little tabs, about 3/16-inch wide, spaced equidistantly around the diameter of the cap. A replacement cap can be identified by looking at the back of the face for the 4 tabs. A very sharp eye might be able to detect one on the car, since between the tabs, the replacement cap doesn't wrap around to the back to the back of case.

Conclusions

Appendices

Servicing the 1967-68 Glovebox Lock

From the B&S Service Manual:

Lock is held in compartment door with screw and retainer cup.

1. Removing Lock Cylinder from Case - Hold bolt down and turn key clockwise until stop. Pull out cylinder.
2. Replacing Bolt, Pusher and Spring - Keep cylinder out of case. Replace pusher, bolt and spring in order indicated. End of spring must rest in knob recess. Use a screwdriver to force other end of spring over button on bolt.
3. Replacing Lock Cylinder - Hold bolt down. Insert cylinder with cam up. Turn key counterclockwise until stop.

With the glovebox cylinder plug out (B&S refers to it as the glovebox cylinder, but from a locksmithing standpoint, it is a cylinder plug that is in need of the case or housing to be a complete cylinder), you will see 5 tumblers. The tumblers are spring-loaded, so one end of each will extend beyond the diameter of the plug when the key is out of the cylinder; when a correctly cut key is in the cylinder, the ends of the tumblers will be flush with the diameter of the plug, allowing the cylinder to be turned, and the catch to be opened.

The trunk/glovebox key code is stamped on the outside of the cylinder plug.

Some older glovebox replacement cylinders were furnished with extra long tumblers staked in; the locksmith "coded" these by inserting the desired operating key in the plug, placing the plug in a special holding fixture, clamping the fixture in a vise, and filing the protruding tumblers to size.

Removal of Dash (1967-68) Ignition Lock

Turn the cylinder as far counterclockwise as it will go, then insert a suitable tool (a partially unwound paper clip works well) in the poke hole in the face to push in the plunger; continue turning counterclockwise, then pull the cylinder.

Re-assembling Door Lockset With New Spring Cover/Face Cap

Replace the plug in the lock case. Put the 2 small dust cover springs in the intentations (in the face of the plug) designed to receive them, place the dust cover over them, then place the face cap over the assembly. If you have a vise available, you may find it helpful at this point to: hold the assembly together by grasping it with a finger at the back of the lock case, and thumb on the face cap; then insert the key in the cylinder. Drape a shop rag loosely over the vise jaws, so you can put the key bow between the jaws (also between areas of the shop rag), and rest the face cap on the tops of the jaws, holding it down, to keep the parts together as you tighten the vise enough to gently hold the key bow. Use a hammer and a fairly large pin punch (up to about 3/16-inch) to tap each of the 4 tabs on the face cap down, to hold the face cap on the lock case. When the face cap is firmly in place, remove the key, and tap the tabs more, as necessary, to get them neatly down.

Distinguishing Between RP and B&S Locks

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