Ray, what is the source of this information?
----- Original Message -----
From: "Ray Boyce" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Thursday, December 27, 2007 3:22 AM
Subject: [BlindHandyMan] Historical Guide to Cabinet Locks
The need to secure precious objects is so innate to humans and many other
animals that it is not surprising the earliest locks appear as long ago as
4000
years. The oldest known locks employed a pin tumbler mechanism much like
that of our modern "Yale" lock but on a far larger scale. They have been
found
in cultures as diverse as those of Egypt, Japan and Norway. The Romans can
be credited with the invention of the metal lock and in fact developed the
"warded
lock" which uses the familiar skeleton key still common enough today. Warded
locks rely on sections of concentric ridges around which the key must fit
in order for it to act on the locks sliding bolt (see diagram below). Time
passed and the increasing complexity of these locks became a source of much
pride to the locksmithing profession and some misplaced assurance to the
person with much to protect. Of course the lock picker was never far behind
these
advances and being engaged in a prideful profession demanded job
satisfaction only more advanced locks could provide. The late 18th century
gave him a
more challenging device, the double action lever lock (see diagram below).
This mechanism is found in most furniture grade cabinet locks today. As the
key slides the bolt into or out of the lock it also moves one or more spring
loaded levers away from the bolt's path. The more levers, the harder the
lock
is to pick.
Warded lock
Lever lock
Today
Today the use of locks on furniture has become somewhat redundant. In
earlier times locks in the domestic realm were intended to frustrate not
outsiders
but children or those in the employ of the household. These days a locked
drawer might deter a passing child but the real predators are more likely to
come from outside and rarely have the time or interest to develop skill in
the craft of lock-picking. Their modus operandi more likely involves the use
of wrecking bars etc and in any case they might realize the contents of a
nice piece of furniture is in all likelihood of less value than the
furniture
itself and simply abscond with the whole thing, locks and all. Whether they
serve any practical function or not, we have become so used to seeing locks
on fine antiques that a drawer without one seems as blank as a face without
a nose.
In many situations the key of a lock served as the handle for a door or
drawer while the lock itself took the place of the catches we are so
familiar with
today. Aside from the finger turn type of catch the 18th century was
remarkably short on door catch technology so the lock would find application
wherever
a door needed positive closure. Today we like the convenience of our
magnetic and ball type catches and often wish to use then on reproduction
style cabinetry.
Attempting to find an appropriate knob or handle to take the place of an
escutcheon and key is no easy matter and leads many otherwise respectable
cabinetmaking
efforts to fail needlessly. It will always be worth the extra effort to do
the job right and fit a lock.
Choices
Traditional cabinet locks are available in an array of mounting, material
and size choices to suit most preferences. Three alternative mounting
configurations
are the "
Half Mortise", "
Full Mortise"
and "Surface Mount" style lock cases. The "Half Mortise" lock is the one
found on almost all fine English and American antiques prior to the middle
of the
19th century. This type of lock is mortised into the back side and edge of
the work and lays flush. The "Full Mortise" lock is mortised into the edge
of
the work. The "Surface Mount" lock is simply screwed to the inside face of
the work. Each of these types has its advantages.
Terms
The various names for the parts of a lock and the definition of a left or
right hand lock are a source of endless confusion!. Here is our glossary.
(Beware:
our definition of left and right hand are the opposite of some others,
including even our own lock manufacturers!)
Bolt - When you turn the key the bolt is the part that projects out of the
lock.
Selvedge - The face of the lock through which the bolt projects.
Plate - The face of the lock onto which the mechanism is attached.
Distance to pin - The measurement from the selvedge to the center of the
keyhole.
Backset - The same as distance to pin.
Full Mortise - A lock whose body is entirely mortised into the wood.
Half Mortise - A lock mounted into a shallow mortise in the back of the
work.
Surface mounted - A lock that is screwed to the back of the work with no
mortising required.
Left Hand - A lock mounted to a door hinged on its left hand edge (or the
reverse, depending on where you get the lock).
Right Hand - A lock mounted to a door hinged on its right hand edge (or the
reverse, etc as above).
Levers - Spring loaded obstructions that the key moves out of the path of
the bolt. The more levers the more difficult it will be to pick the lock.
Half Mortise Locks
Half mortise lock The half mortise lock strikes a good balance between ease
of installation and unobtrusive utility. The work necessary to fit these
locks
makes greater demand on finesse than muscle, all the cuts are of the wide,
shallow nature rather than the more problematic narrow, deep variety
demanded
by the full mortise lock. This attribute suited the pre-power tool
cabinetmaker. Because the half mortise lock is always registered against the
inside
surface of the work the bolt is biased to the rear. Traditional
cabinetmaking accommodated this rearward bias with casework drawer dividers
constructed
of sufficient width material. In modern face frame construction this
characteristic can lead to problems and either the full mortise or surface
mounted
lock could be a better choice.
Half mortise locks were rarely paired with a strike plate. The bolt of the
lock would engage into a simple mortise cut directly in the adjacent
woodwork.
Aside from the remote possibility of catastrophic wear taking place there is
no downside to this method. Strike plates serve no useful purpose and cost
the cabinetmaker time and money.
Due to the internal mechanical layout of the half mortise lock the key is
invariably off center in relation to the lock body. Before laying out the
cuts
for these locks take note of this fact!
Full Mortise Locks
These locks were virtually unknown before the days of mechanized
woodworking. Because a full mortise lock is fitted into a deep mortise
Full mortise lock cut into the edge of the work it is troublesome to install
without a mortising machine, with one it could hardly be easier. The reverse
is true of the half mortise lock.
Though conceived with rapid and mechanized installation in mind they are not
without some drawbacks. The bolt will generally be centered in the work
rather
then biased to the rear as in the case of the half mortise lock. This may
result in certain benefits related to constructional simplicity but also
brings
the bolt nearer the front of the casework making it more likely for that
area to break out under force (a strike plate can compensate by reinforcing
this
area).
A full mortise lock can also be a problem installed in thinner material. For
any given lock thickness a full mortise lock will leave two walls half the
thickness of the one wall left by a half mortise lock. An additional minor
consequence of this forward positioning is the attachment of the keyhole
escutcheon.
Keyhole escutcheons are normally attached with brass escutcheon pins. If the
wall thickness left after the lock mortise is cut is limited then these pins
will have little to secure themselves to.
As with a half mortise lock, the keyhole is off center in the lock.
Surface Mount Locks
Surface mount locks are simply screwed to the back of the door or drawer
front, no cutting required. Most surface
Surface mount lockmounted locks have a dual keyhole allowing them to
function as both hands of door lock as well as a drawer lock. The keyhole is
usually
centered in the upright width of the lock and the bolt can exit from either
side depending on which way the key is turned.
The bolt of a surface mount lock will engage behind the adjacent face frame
or door to prevent opening.
These attributes make surface mounted locks versatile and popular, but like
many things easy and convenient they are not going to impress anyone with
their
refinement. Surface mount lock appears to have historical credibility on
country styles of furniture particularly as door locks but should probably
be
avoided on more formal work.
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