from the locksmith dictionary says;
cross bore is a hole bored or drilled into the face of the door.
cross bore usually goes completely through the door but there are communicating
door locks that don’t require the hole through the door, just into it. The
edge bore is a hole bored or drilled into the edge of the door so that it
intersects the cross bore.
are some important features about the cross bore that need to be considered,
especially if you are replacing an existing lock.
is the distance from the leading edge of a door to the center of the cross bore.
Two dimensions are typical in the US, 2 3/4" and 2 3/8”.
There are other standard backsets that have been used and one that came
close to being a standard is 5 1/2".
important dimension is the diameter of the hole used for the cross bore.
Most locks available in 2008 have a 2 1/8” diameter but there are other
size requirements for some brands. If
you have a different diameter hole in your door that is too small, there is
some good advice for redrilling the cross bore in the Redrilling a Door article.
If the cross bore is too large now your easiest option is to plug the
hole and redrill it.
bored locks only require one of each type of hole, but there is a type of bored
lock that requires more than one, the interconnected lock.
are two general types of bored locks;
cylindrical lock has the locking mechanism in the part of the lock mounted via
the cross bore. You can check the type easily by holding the lock part
that mounts through the cross bore and trying to lock it in your hand. If
the knob or lever won't turn, it is a cylindrical lock, if it will turn, it is a
lock is typically a deadbolt that is mounted separately from the key-in-knob or
lever lock. The original intent of
the deadbolt was to be a secondary locking device to be used when no one
was occupying the building.
are two types of deadbolts, the single cylinder and the double cylinder.
The single cylinder only requires a key to operate it from the outside
while the double cylinder requires a key from both sides of the door.
municipalities have outlawed the double cylinder deadbolt because people have a
tendency to lock them when they are in the building and that poses a hazard if
there should be a fire or some other reason to leave quickly.
In a panic situation such as a fire very few people will have the
presence of mind to get a key to unlock the door. It also may be hard to
find a key hidden near the door when the room is filled with smoke and fire.
locksmiths discourage the installation of double cylinder deadbolts because of
this hazard but there is an alternative if you feel you require a double
cylinder lock. There are dead bolts
on the market that capture the key inside and won’t release it until some
other extra step is performed. That
typically should discourage not having a means of exit without consciously
choosing to remove the key.
Knobs and Levers
next type of bored lock is the key-in-knob or key-in-lever lock so typical in
the US. The same dimensional
features are just as important with these types of lock and either type may be
cylindrical or tubular in function.
common shape has traditionally been a knob and the outside knob typically has a
keyhole in it. Along with the Americans with Disabilities Act mandates we
have started seeing that tradition change. It is becoming more common to
see lever handles in these applications.
most important feature to examine on these types of lock are the latch itself.
Check the article on latches for details.
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