GM Six Cut Door/Trunk Locks

By T.F. Stern, GSP

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Being an “Old timer” I sometimes forget how the newer generation automotive locksmiths might not run across the Six Cut GM Door/Trunk lock all that often.  This morning I was reminded of this when I had a chance to show a fellow locksmith how to generate a key for a 1995 Camaro door lock that he’d already pulled out of the door cavity.

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He asked what was the best way to generate a door key so I explained how there is a storage compartment in the back of the car, much like a glove box.  The lock is easily removed and has 4 of the 6 wafers from which to get started.  Once those cuts are known the last 2 cuts can be determined via a simple progression series which eliminates the remaining cuts; no more than 3 key blanks are used and it is time efficient.

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Since the lock had already been pulled and the car was not readily available the next best way to generate a key would be to field strip the door lock.  I use a  Gator Tool ® to remove the cap so it can be re-used rather than have to use a replacement cap; if done properly it looks more professional and fits better.  Once the cap has been removed make sure to keep track of the weather guard and two small springs which keep the weather guard in place; put them off to the side until the lock is ready to be reassembled.

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The GM door lock is a side bar lock and requires “mild” pressure on the side bar while picking for the wafers to remain in the picked position.  I recommend inserting a blank key prior to picking, glancing at the relative position of all six wafers when they are at the “no cut/one cut” position within their respective slots.  By doing this a comparison can be made once they have been picked.  Another “trick” to reading these wafers is to lightly “score” the top of each wafer with a sharp instrument so it reflects light more easily; often times these locks have considerable oxidation which makes it more difficult to see them, especially on deeper cuts.  Rake the wafers until the side bar drops and then read the depths of each wafer to determine the cuts.

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There is a simple rule to remember on the older GM Six cut keys; “The sum total of all the cuts will add up to an EVEN number”.  This rule makes it a bit easier in figuring out those cuts which are hard to see.  If the first 5 cuts are fairly certain; add up the cuts you already know, if they add up to an even number then the unknown cut will also be an even cut so that the total will come out even.   If the first 5 cuts add up to an odd number then the unknown cut should be an odd number as well.  This rule, while not written in stone, applies to 99 % of GM Six cut locks.  (There are a few odd balls out there; most notably after market replacement locks made in South America.

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There are several ways to cut the GM Six cut key; but I prefer using the  Pak-a-Punch hand held cutter.  For years I used Curtis’ “14 Cutter”, then their “15 Cutter”; but the Pak-a Punch has become my favorite.  Other locksmiths use electric code machines and there are some very nice ones out there; Framon and HPC come to mind as quality machines that are popular.  Which ever machine you pick it should fit the type of business you are most comfortable with.

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As I mentioned earlier; the first choice would have been to figure out the cuts to the “auxiliary” lock or glove box lock.  Once the first 4 cuts are known and have been placed on the proper key blank then finding the last 2 cuts is a “piece of cake”; just don’t say that too loud or the “Billy Crystal Curse” might rare up and bite you in the butt.  The principle behind elimination of the last 2 cuts is dependent on these locks being Original; if at any time these locks have been replaced then they likely won’t have been matched up to each other.  I use a hand held cutter because it is the most efficient way to eliminate those last two cuts in the field.  I’ve heard others praise the use of electric code machines, that they are just as efficient; each to his own.

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I’ll take a moment to include the GM Six cut trunk lock at this time.  While it is basically the same as the door lock; the trunk lock requires the plug to be turned in order to disassemble.  There are a couple of ways to accomplish this; drilling an access hole directly over the side bar has worked well and does no significant damage to the housing so it can be reused rather than thrown away.  (Use a small drill bit, 1/8th or smaller)

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Once the drill bit clears the lock housing it is important not to keep on drilling into the side bar; a gentle hand is required.  This is all done after the face cap has already been removed so you can feel the plug move without being “pinched” while being clamped in your vice.  Insert a small nail set or wire into the newly drilled access hole in order to apply “mild” pressure on the side bar while picking.  Once the side bar drops, and you can feel it drop with just a little practice, then turn the plug and remove it from the housing.  Fit the key as explained above under GM door lock.

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One last item on the GM Six cut trunk lock.  You will want to clean up the side bar channel from any burrs created by drilling the access hole.  This is accomplished by pushing the blade of a small flat blade screw driver along the channel until it glides without resistance.  If this is not done the side bar may not drop sufficiently and the lock will not function properly.

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The wafers on GM Six cut locks sometimes refuse to glide up and down the way they did when they left the factory.  Any number of reasons, age, dirt, abuse or attempted force can damage the wafer of the slots in which they ride.  If the lock requires a complete tear down; remove the spring cover cap, springs and wafers as needed.  These can be replaced; but if you were unable to figure out the combination it is important to carefully remove and note the position of each wafer so as to determine the combination.

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It has been recommended that a new spring cover cap be used when putting the lock back together.  This rule could easily be extended to the springs; replace all the springs and know the job was done properly.

There are some “professional” locksmiths who believe that any alteration of the original lock design constitutes a lapse in National Security.  The Russians and Chinese armies are waiting at our borders waiting for some locksmith to throw away one of the six wafers setting off alarms and whistles in a bunker deep inside a mountain where Norad monitors lock assemblies.  Then again, do what is called for “under the circumstances”, your eternal soul hangs in the balance, in all probability you won’t spend the eternities in outer darkness.  (Hope you can read between the lines).

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Replace the weather guard, springs and face cap; keeping everything in place with a screw driver gently placed on the weather guard until the face cap is seated.  When putting the face cap on place the entire assembly against something sturdy like the base of your shop vice.  Use a small ball peen hammer to gently push the edges of the face cap back into their original shape; avoid getting in a hurry and most folks couldn’t tell the cap had ever been removed as it will appear “round”; not like the replacement caps which tend to look like “stop signs” with an angular appearance.

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Most of the information shared here can be applied to other locks which use a side bar; GM Ignitions, Ford Ignitions and some Dodge Chrysler locks as well.  Believe it or not, GM actually stamped code numbers on door locks until about 1971; times were simpler then.

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January 10, 2012 at 12:24 am by admin
Category: Uncategorized