Maintenance and Repair of Locks

THERE are many variations in lock design and innumerable specialized uses which determine their size and shape, but for the purpose of this entry only the more orthodox types, for use on doors, are described. These consist of the spring latch, the locking latch, the dead locking latch, the dead lock, the mortise lock, the rim latch and pin-tumbler lock.

A latch is a fastening device which can be operated without a key; the commonest sort is the thumb latch used on gates and outhouse doors. Spring latches are often used on cupboard and room doors. This latch may be operated from one side, or from either side, by turning a handle. When the door closes, the bolt (which has a bevelled end) is pushed in by the striking plate fixed to the door frame, and springs out again into the slot in this plate, so fastening the door until the handle is turned.

A spring latch is incorporated in many door locks, properly so called, and usefully applied as a night latch when fixed to exterior doors. On leaving the house, or entering it after having used the key, the latch fastens itself automatically when the door is pushed to the closed position. Inside the house the latch bolt can be opened by turning the handle; from the outside it can be operated only by the key. This is more properly known as a locking latch, and is the principle upon which the pin-tumbler latch (Yale pattern) works.

Most room doors have a locking latch. That is, the lock has two bolts, the spring bolt, acting as described above, and the locking bolt, which must be shot or drawn back by using the key. So the door can be opened (provided it has not been left in the locked state) by merely turning the handle. Locking latches, even of good quality, unless fitted very securely, may be opened by force.

For extra security a dead locking latch, or a plain dead lock can be substituted. This must be locked or unlocked by a key. Thus, if the householder takes the trouble to lock the door behind him, it is secure against unauthorized entry, even if a pane in the door should be removed. An alternative is to fit a dead lock in addition to the ordinary night latch, using the dead lock on occasions when the house is to be left unattended. People are apt to be careless of security in the matter of locks on outer doors. An extra ten or fiteen shillings spent on having better or more secure locks will perhaps save many pounds.

Fitting a Lock to a Door

Good practice is to use a mortise lock, which is let into the edge of the door; as a result no one can tamper with the lock mechanism. But on less important doors the rim latch is more often fitted; this is merely screwed to the face and the edge of the door,. The fitting of a mortise lock to a door is a difficult task which should be undertaken only by a skilled craftsman. When a lock is to be fitted to a new door (for instance, that of a shed or outhouse), it is better to use a rim latch. Also, if the mortise lock of a door goes wrong owing to the wood of the mortise breaking out, a rim latch can be substituted, if the old lock is taken out and the mortise and other holes are carefully plugged. So here are given instructions for fitting the rim lock or rim latch only.

Purchase a rim latch, or rim lock, according to the situation and the requirements of the door.

This lock incorporates a spring bolt, turned by the handle, and also the locking bolt. A box staple, for screwing to the face of the door frame, should be bought to suit. It will be seen that the lock has a flange that fits against the edge of the door; in cheap types this flange has no screw holes.

Place the latch on the door, in the position, and pencil around the outer margin, both on the face and the edge. Cut out the shallow recess needed to set the flange in flush with the wood surface.

Quite often, in poor work, the flange is merely screwed on, not recessed into the wood. Put the lock in position again, and while it is held tightly against the door edge, mark with a fine bradawl the centre which will locate the position of the hole to be bored for the handle spindle.

The door should be shut, or wedged in the open position, while boring.

When this operation has been completed, put the latch in place, and push the handle spindle through. Verify that it works easily, and that when the latch flange is hard up against the door edge there is no hindrance to its rotation. Make any adjustment needed, by rasping the hole towards one side, or slightly deepening the recess for the flange (though little can be done safely here). Put two screws through the lock into the door face.

Test the handle again after screwing. If all is well, mark the two holes E, from which the keyhole will be cut. Bore these holes, and connect them to form the keyhole slot; leaving enough clearance, but no surplus. Clean the slot carefully, and fasten the latch to the door again, using two screws only for the time’ being. Try the key in the lock, when it should function easily.

It remains to fix the box staple to the face of the door frame with the two long screws that should have been obtained for it. If the door has an architrave moulding, this may need cutting back a little to allow the staple to be fitted flat, in direct line with the latch. Shoot the lock bolt, and try the staple over it to find the proper position. Then screw the staple in place; try the lock again, and if satis- factory, insert the remaining screws in the face of the lock, and also those through the flange on the edge. Enough clearance must be allowed between edge of lock and the striking part of the staple, but not too much.

Care of Locks

Put a little oil on the spring bolt occasionally. At the same time observe if the hinges are in proper order, and oil them. When the action of a lock seems weak it is probably the spring that is faulty; more often the latching bolt will show this trouble. Sometimes the handle itself is fitted with a return spring inside the casing. Assuming that the handle is in order, take off the lock and open its casing. From a study of what has been said above, the rim lock will be easily removed. Take off one knob or handle, by undoing the locking screw or stud that attaches it to the squared spindle; sometimes the hole in the knob is threaded, while that in the spindle is plain, but this order may be reversed. Withdraw the spindle and proceed in the following manner:

Unscrew the lock from the door and brush off any dust from the back of the casing. One or two screws will be seen, which secure the back plate to the case; remove these screws and put in a safe place. Gently prize off the back plate; take care that the contents of the lock do not spring out and become mixed, as identification of the parts, for the purpose of reassembly, may be difficult/ This will not matter so much when we have noted and memorized the fitted positions of the parts. A double flat spring will be seen which operates the bush in which is the squared hole for the spindle. This is the one most likely to have become weak, and the one that most frequently breaks. If the spring seems weak (it can be tested by turning the follower, without dismantling the parts), take it out and buy a similar one at the locksmith’s or ironmonger’s. They are quite inexpensive. If too long in one or both arms it can be cut off short with a pair of side-cutting pliers. If the end is jagged, hold it against a grindstone or bench grinder.

Before replacing the spring, brush out all dust, and give the working parts a touch of oil; another opportunity may not come for a long time. Bad rusting can be treated with paraffin and the parts rubbed bright with emery cloth.

The removal of a mortise lock is a little more difficult. Take out the spindle as before; unscrew the face plate on the edge of the door. When fitted on good locks, this plate is secured to the end plate of the lock by two metal screws; after removing these the two wood screws that fix the end plate of the lock in the door will be accessible. Having removed the two wood screws, withdraw the lock from the mortise ; a screwdriver can be put through the spindle hole to assist, but take care not to damage the door or lock. The lock casing may be opened by unscrewing the securing screws of the casing cover plate. As the working parts in a mortise lock are closer together, more care must be taken to note the fitted positions of the components. In other respects the procedure for replacement of springs, etc. is as for the rim lock. Striking Plates and Staples

If a door drops or warps, the position of the striking plate (or, in a rim lock, the box staple) may be wrong, and the holes will not register with the bolts of the lock. After any necessary adjustment has been made to the door itself, the plate or staple should be moved so that it registers correctly with the end face of the lock.

Pin-Tumbler Lock

These, of the Yale pattern or other type, are in almost universal use for entrance doors. When fitted by the builder they seldom give trouble, though the staple may have to be adjusted for an alteration in the position of the door in course of time. As with mortise locks, the fitting of a pin-tumbler lock is a job for the skilled craftsman, who will also possess tools and gauges to facilitate lock fitting. Sometimes when all keys are lost the lock itself has to be taken to the ironmonger for a new key to be made by reference to the lock. Take out the long screws securing the body of the lock to the back of the door, then those that hold the cylinder will be accessible and can be withdrawn. It is better not to tamper with the cylinder; deliver it, intact, to the locksmith.

When keys are to be cut from a pattern key, give the locksmith the original key, not one made from that key, which, may vary slightly from the original sold with the lock. This applies particularly to pin-tumbler locks, but generally to all types. If possible, get the keys cut by a competent locksmith. It is better to obtain a hand-cut key from a good locksmith, rather than an indifferently duplicated key, cut by an unskilled operator.

Sorry, comments are closed for this post.

Share On Facebook
Share On Twitter
Share On Google Plus