PROPER DRILLING OF PIN TUMBLER PLUGS
I had assumed for a long time that all professional locksmiths know how to drill
the shear line of a pin tumbler lock, but when I had to replace a very expensive
commercial duty Schlage lockset after an employee, who'd been hired as an
experienced locksmith, drilled incorrectly and wiped out the mechanism behind
the plug entirely.
If it is not possible to pick a pin tumbler lock, and no other entry seems open
to you, drilling the plug is the accepted "last resort" method of
entry. If it's done correctly, there is no damage to the lock mechanism – just
to the plug, which can be replaced easily and inexpensively.My
employee had the impression somehow that drilling is to be done at the center of
the keyway, and when a half hour of drilling and cranking on the knob failed to
open the door, he just kept drilling deeper and deeper. Annihilation of the
lockset ensued.
The shear
line is where you want to attack the plug. This keeps the drill bit within the
plug itself, but high enough toward the shear line that the pin tumblers will be
eliminated by the bit and eventually nothing will be left to prevent the plug
from rotating in the shell.
Begin by
placing a center punch at dead center vertically but above the keyway
horizontally, as shown below.
Make a
good dent with the center punch to guide the drill bit. Use a bit no larger than
1/8" and choose a brand new one if possible. Brass is relatively soft, but
the pins will rotate when struck with the spinning bit and they will quickly
dull a used bit to the point of uselessness. A new one has a much better chance
of doing a clean job.
Keep the drill level. Continuously monitor yourself or have a partner watch as
you travel inward with the drill. If you drill at an angle, you'll make the job
harder and you could stray beyond the limits of the plug and do damage to the
lock, rendering it incapable of accepting a new plug.
As the bit
passes through the initial metal stock of the lock face, you'll feel a moment of
less resistance. It will then encounter the first pin tumbler (more resistance).
Put heavy pressure on the drill motor as each successive pin tumbler is
encountered. Count them as the bit first encounters them and then chews through
them. Most locks have five tumblers – some have six. After counting the
destruction of five tumblers, stop. Clean out the hole as best you can, insert a
heavy screwdriver with a blade that fits well in the keyway, and turn the plug.
It may require alternately forcing the plug one way and then the other to coax
debris out of the shear line. If this doesn't work after a while, drill the hole
again, going no further than before, but slightly reaming the hole larger. Try
to turn the plug again.
If the
plug will not turn, you may have a 6th tumbler to get rid of. Start drilling
again, applying force carefully. If the bit does not almost immediately
penetrate another tumbler, STOP. You're probably drilling through the back of
the plug now and you don't want to risk going any deeper.
If this is
the case, it's simply going to require more persistence in cleaning the brass
debris out of the drilled hole. The plug WILL turn if you have placed the drill
point in the right place and have drilled out all the tumblers.
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