The value of a lock depends much upon the way in which the parts are planned, and as no two manufacturers use exactly the same arrangement, it is difficult to compare locks of different makes without considering them in detail. Nearly every manufacturer, however, makes different grades* of locks, which may in general be described as follows:
Second. - Locks with brass face and bolts, all the rest of iron, one lever.
(This is probably the best grade of one-tumbler locks.)
Fourth. - Same as third, with two, three or four levers. Each grade is usually made in 3 ½ and 4-inch sizes for inside knob locks.
As a rule, a 4-inch lock of the fourth grade with three levers is as good a lock as is needed for the inside doors of dwellings. Of course, even in this grade there are differences between the locks of different manufacturers, and between a cast lock and a high-grade machine-made lock. A lock that is made with fifty " changes " in the gatings is also to be preferred to one with only twelve or twenty-four changes, as there is less chance of any two keys in the building being alike.
*The term "grade" is here used to designate differences in the materials used, and the number of levers and changes, rather than the quality of the work, as some manufacturers make their cheaper locks equally as well as the better grades.
For heavy doors, especially in office buildings, an anti-friction latch may be specified, although this latch does not appear to be as much used as formerly. When greater security than that afforded by a three-lever lock is desired, a "cylinder" lock should be specified.
2l8. Varieties of Tumbler Locks. - Tumbler locks are made of several different styles or patterns to suit different purposes. These are classified as knob latches, knob bolts, dead locks, store door locks, knob lock and latch, three-bolt chamber door lock, communicating door knob latch with thumb bolt, communicating door knob lock, front door and vestibule locks, sliding door locks, master keyed locks and sliding door locks.
Dead locks knob locks and hotel locks are made both rim and mortise, and rim knob locks are also made with thumb bolts, but the other varieties are usually found only in mortise locks.
Fig. 374 - Knob Latch.
Fig. 375. - Knob Bolt.
Fig. 376. - Dead Bolt.
Front door, store door and the common mortise knob lock and latch may be obtained with either plain or rebated fronts, but the other patterns are made only with plain fronts, except that sliding door locks are made with astragal fronts.
A rebated lock is made the same as a plain front lock, except that the front is rebated, as in Fig. 382, to fit the rebated edge of the door. Rebated locks are used only on double doors, and are necessarily made in right and left hands.
Knob Latch (Fig. 374.) - This contains only the latch bolt and its accompanying mechanism, operated by knobs and spindle, and is used only where a lock is not desired - occasionally on closet doors.
Knob Bolt, Fig. 375, contains a simple dead bolt operated by a thumb knob from the inside of the door. Frequently used on outside doors and chamber doors for additional security, as it cannot be picked from the outside. Takes the place of the common surface bolt on account of neater appearance.
Dead Lock (Fig. 376.) - This is a simple lock without a latch, and is operated by a key from either side of the door. It is used principally on store doors, double-action doors, and where an additional lock is desired. For store doors a lock with a wide bolt and at least three tumblers should be used.
Store Door Locks (Fig. 377.) - The regular store door lock consists of a case containing a strong dead bolt operated by a key from both sides of the door, and also a latch bolt operated independently by a thumb latch from either side. The thumb latch and handle enables heavy doors to be more easily swung than by knobs, and the door being usually locked only at night, a spring bolt is not necessary. Store door locks of the better grade are usually fitted with "cylinder escutcheons." The locks are made in several sizes, and may be had with stop work, by setting which the outer thumb latch is dogged so that no one can enter without a key.
Fig. 378. - Knob Latch with Thumb Bolt.
Fig. 379. - Knob Lock and Latch.
Fig. 380. - Three-Bolt Chamber Door Lock.
while those inside may leave freely. A store door lock with stops is practically a front door lock operated by a thumb latch instead of knobs, and is often used on outside church doors.
The Yale & Towne Manufacturing Co. also make a special store door lock for double-acting doors.
Knob Lock and Latch (Figs. 378 and 379.) - This is the common form of lock and latch generally used on inside doors, the mechanism of which is described in Sections 214-15. Aside from the quality and mechanism, the variations in this lock consist principally in the size of the case and in the "back set." The common sizes are 3½ and 4 inches or 3¾ and 4¼ inches, according to the make. The larger size should be specified for heavy doors.
The back set is the distance from the edge of the door to the centre of the hub. This distance varies in different makes of locks, and each manufacturer makes locks with different back sets to suit different conditions, the distance being always given with the description of the lock.
The more common back set is 2 ¾ inches, although on 3½-inch locks it is often but 23/8 or 2½ inches. For doors with a narrow stile an upright lock (Fig. 381) may be had, with a back set of only 1 7/8 inches or even 1 inch. When the back set is less than \\ inches, however, a lever handle, such as shown in Fig. 398, should be used.
If the stile of the door is very wide, a lock with a back set of 3 inches may be had, which gives greater clearance between the hand and the door jamb. When designing an ornamental door, the back set of the lock and also the size of the knob and escutcheon should be considered, that they may come well on the door and not be too wide for the stile or interfere with any mouldings.
The Three-Bolt Chamber Door Lock, Fig. 380, is an ordinary knob lock and latch with an additional bolt below the key bolt, operated from the inside by a thumb knob. This is a very desirable lock for the chamber doors of private residences.
For "communicating doors" - i. e., doors between two chambers or offices - two styles of locks are used, the simplest (and cheapest) being the communicating door knob latch (Fig. 383), which has a latch bolt and two dead bolts, operated by thumb knobs, one on each side of the door so that the door may be perfectly secured from either side. This lock may also be used for water closet doors between rooms. The other style is the communicating door lock (Fig. 384), which is a knob lock and latch with the addition of two dead bolts operated one from each side of the door. The advantage of this lock over the latch is that the door may be locked with a key so that the occupants of the two rooms cannot communicate with each other without picking the lock. It is particularly adapted to communicating doors of hotels and lodging houses.
Fig. 382. - Rebated Front.
Fig. 383. - Communicating Door Latch.
Fig. 384 - Communicating Door Lock.
The Russell & Erwin Manufacturing Co. make a mortise knob lock with two key bolts, operated from disconnected key holes, so that when locked from one side it cannot be unlocked from the other. This differs from the lock shown in Fig. 383 only by the bolts being operated by a key instead of a thumb piece, which might be an advantage in some cases.