Locksmithing -- Types of Locks and Keys

Most people have a general understanding of what a lock is, but that under standing is often limited to the few models they've owned or seen. Few non locksmiths know much about the wide variety of locks that exist throughout the world or how locking technology has changed over the years. That's why many general consumer books and articles about locks (which are almost always written by nonlocksmiths) use definitions of the term lock that are too narrow, broad, or outdated. Although laypersons might not need to be concerned about the misleading definitions, it's important for a locksmith to know what a lock really is and isn't.

What Is a Lock? Coming up with clear and precise definitions of lock isn't as easy as you might think. To see what I mean, write down your best definitions before reading further. After you read this introduction, look at them again.

A professor had a hard time figuring out what a lock is. In his guide on locks, he suggested that a stone rolled in front of a cave may have been the first "lock," and that rolling the rock away was "picking" the lock. He also called guard crocodiles in moats "living locks," and wrote that drugging them is picking the locks. "A lock, after all, is simply a barrier or closure, a way of sealing up an entryway, of keeping what you want in, in, what you want out, out," Washington wrote. "A stick or doorstop that you wedge under a door…is also a lock, though, again, not a reliable or unpickable one." Although it's creative, such a broad all-encompassing definition has no practical value for the locksmith or anyone who works with, uses, or needs to buy a lock. Also, it shows that that person doesn't know what lock picking means because a rock, crocodile, and stick are unpickable--as is any thing without a keyway.

Major dictionaries are more precise in their definitions. The latest Random House Dictionary says a lock is "A device for securing a door gate, lid, drawer, or the like in position when closed, consisting of a bolt or system of bolts, propelled and withdrawn by a mechanism operated by a key, dial, etc." Webster's Third New International Dictionary, unabridged, says a lock is "A fastening (as for a door, box, trunk lid, drawer) in which a bolt is secured by any of various mechanisms and can be released by inserting and turning a key or by operating a special device (as a combination, time lock, automatic release button, magnetic solenoid)." Those dictionary definitions are much better than the "locks are all things that hold, hide, fasten, or bite" kinds of definitions. High-quality dictionaries don't just make up definitions; they try to keep up with standard usage, based on a wide range of sources. As explained in the Merriam Webster's Collegiate Dictionary: "The ever expanding vocabulary of our language exerts inexorable pressure on the contents of any dictionary. Words and senses are born at a far greater rate than that at which they die out." The locksmithing field progresses faster than the dictionaries update the related terms, which is why dictionary definitions tend to be a bit dated and exclude some current types of locks and locking technology.

A more precise definition of lock is given by the International Association of Home Safety and Security Professionals: "A device that incorporates a bolt, cam, shackle or switch to secure an object-such as a door, drawer or machine-to a closed, opened, locked, off, or on position, and that provides a restricted means of releasing the object from that position." One important difference of that from many of the other definitions is the matter of "restricted means." If anyone can just turn the doorknob and walk in, there's no restriction. That's why a set of doorknobs isn't a lock but a key-in-knob is.

If you tried to make up your own definition of lock, ask yourself three things about it: (1) Does your definition include padlocks? (2) Does it include car ignition locks? (3) Does it exclude a chair wedged under a doorknob? If you can honestly answer Yes to all three, you could be an English professor.

Lock Names:

Most locks have several names, which are usually based on a lock's common uses, appearances, major security features, installation method, internal construction, technology, or manufacturer. Many of the names have overlap ping meanings. Some names based on common usage, like trailer lock and bicycle lock, are specific enough to be used by locksmiths as well as laypersons because there are few significant variations among such locks. That is to say, one trailer lock isn't much different from another trailer lock.

Other names based on common usage, however, like house lock and car lock, refer to too many different types of locks. A locksmith would be confused if, say, a homeowner simply asked for a new "house lock." The home owner would need to be more specific. He or she would need to ask for a key in-knob or lever lock (names based on the style of handle a lock uses). Other common "house locks" might include an interlocking deadlock or deadbolt lock, whose names are based on important security features.

While talking with one another about servicing locks, locksmiths often use names that describe a lock's installation method or internal construction, such as rim, mortise, and bored. A rim lock is any lock designed to be mounted on the surface (or rim) of a door or object. The interlocking deadbolt is one type of rim lock. Amortise lock is installed in a hollowed out (or mortised) cavity. A bored (or bored-in) lock is installed by cross-boring two holes-one for the cylinder and one for the bolt mechanism. Warded, lever tumbler, disc tumbler, and pin tumbler are names that describe a lock's internal construction.

+=+= A trailer lock guards against tow away theft of unattended boat, camping, snowmobile, horse, mobile home, and utility trailers. (Master Lock Company)

+=+= The U-shape design is common for bicycle locks.

+=+=A key-in-knob lock is one of the most common locks used on homes. (Master Lock Company)

+=+=A lever lock is basically a key-in-knob lock with levers rather than knobs. (Master Lock Company)

+=+=A deadbolt lock is one of the most secure types of locks commonly found on homes. (Arrow Lock Company)

+=+=6 An interlocking dead bolt, or "jimmyproof deadbolt," is often used on front doors of homes.

+=+=7 Most of a mortise lock is installed in a cavity or cutout. (Arrow Lock Company)

+=+=9 Warded padlocks are for low-security applications. (Master Lock Company)

+=+=8 Warded bit key locks come in rim and mortised styles. (Taylor Lock Company)

Warded locks:

A ward is a fixed projection designed to obstruct unauthorized keys from entering or operating the lock. One old type of warded lock comes in a metal case, has a large keyhole, and is operated with a bit key (commonly called a skeleton key). Such locks, called bit-key locks, come in mortised and surface mounted styles, and are often used on closet doors and cabinets.

Some low-cost padlocks are also warded. Such a padlock can be identified by its wide, sawtoothlike keyway and keys with squared cuts. Warded locks provide little security because wards are easy to bypass with a stiff piece of wire or thin strip of metal.

Tumbler locks:

Tumblers are small objects, usually made of metal, that move within a lock cylinder in ways that obstruct a lock's operation until an authorized key or combination moves them into alignment. There are several types of tumblers; they come in a variety of shapes and sizes and move in different ways.

Because tumblers generally provide more security than wards, most locks today use some type of tumbler arrangement either instead of or in addition to wards.

A typical key-operated cylinder consists of a cylinder case (or housing), a plug (the part with a keyway), springs, and tumblers. The springs are positioned in a way that makes them apply pressure to the tumblers. The tumblers are positioned so that when no key is inserted, or when the wrong key is inserted, the spring pressure forces one or more of the tumblers into a position that blocks the plug from being rotated. When the proper key is inserted into the keyway, however, the key moves the tumblers to a position that frees the plug to turn.

A lock can have more than one cylinder. A key-operated, single-cylinder lock has a cylinder on one side of the door only (usually the exterior side) so that no key is needed to operate it from the other side. Typically, it can be operated from the non-cylinder side by pushing a button or by turning a knob, handle, or turn piece. Key-operated, double-cylinder locks require a key on both sides of a door. Many local building and fire codes restrict the use of double-cylinder locks on doors leading to the outside because the locks can make it hard for people to exit quickly during a fire or other emergency.

Types of tumbler locks. There are three basic types of tumblers: lever, disc, and pin. Most lever tumbler locks, such as those used on luggage, brief cases, private mailboxes, and lockers, offer a low level of security. The lever tumbler locks commonly found on bank safe-deposit boxes are specially designed to offer a high level of security. Disc tumbler locks offer a medium level of security. They're often used on desks, file cabinets, and automobile doors and glove compartments. Pin tumbler locks can provide medium to high security, but in general they offer more security than do other types of tumbler locks. Many prison locks and virtually all house locks and high-security padlocks use pin tumbler cylinders. Some automobile door and ignition locks also have pin tumblers.

A special type of pin tumbler lock, called a tubular key lock (or tubular lock), has its tumblers arranged in a circular keyway. It uses a tubular key to push the tumblers into proper alignment. Because of its odd appearance, a tubular key lock is harder for most people to pick open than are standard pin tumbler locks. Sometimes erroneously called "Ace Locks" (which is Chicago Lock Company's trade name for some of its tubular key locks), tubular key locks are often found on vending machines, laundromat equipment, bicycle locks, and high-security padlocks.

Another type of pin tumbler system is found in interchangeable core (IC) locks. Although they come in the form of deadbolts, key-in-knobs, rim locks, mortise locks, padlocks, and desk and cabinet locks, all locks in an IC system can either use the same key or be masterkeyed. Some examples of IC locks are shown. The common feature of IC locks is a figure-8-shaped core that houses the tumblers and springs. The cores can be easily removed and replaced. Any IC lock can be rekeyed simply by inserting new cores in the locks.

+=+= A cross-section of a tubular key lock.

+=+= Types of IC locks. (Arrow Lock Company)

+=+=12 An IC core can be inserted into many different IC locks. (Arrow Lock Company)

Other types of locks:

Combination locks are popular alternatives to key-operated models. The two basic styles are pushbutton and dial. Pushbutton combination locks are operated by pushing a specific sequence of buttons, which are usually labeled with letters or numbers. Dial combination locks are operated by rotating one or more dials to specific positions.

An electrical lock can be operated by electric current. One type, sometimes called an electric lock, is basically a bolt or bar mechanism that doesn't have a keyed cylinder, knob, or turn piece and can't be operated mechanically.

Another type, called an electrified lock, is a modified mechanical lock that can be operated either mechanically or with electricity. Electric switch locks complete and break an electric current when an authorized key is inserted and turned. An automobile ignition lock is an example of such a lock; after the key is turned, electricity flows from the battery to the car's starter.

Similar locks are also used on alarm system control boxes to arm and disarm the system.

Time locks are designed to be opened only at certain times on certain days. They're commonly installed inside bank vaults and safes. Biometric locks unlock only after a computer has verified a physical feature, such as a fingerprint, signature, voiceprint, hand geometry, or the pattern of the retina of the eye.

+=+=13 Some combination locks use pushbuttons. (Simplex Access Controls Corp.)

+=+=14 Many padlocks have dial combinations. (Master Lock Company)

Lock Grades: The American National Standards Institute, Inc. (ANSI) determines manufacturing standards for a wide variety of building hardware and other products used in the United States. Many manufacturers make sure their products meet or exceed ANSI standards because architects, home builders, locksmiths, and other professionals specify products based on the standards.

As a rule, ANSI doesn't create standards. Interested industry associations usually create and propose standards and ANSI reviews them for possible adoption. The current standards for door hardware, listed under ANSI section 156, were proposed by the Builders Hardware Manufacturers Association, Inc. (BHMA).

ANSI 156 is of special importance to locksmiths. That section includes standards for many products locksmiths sell and install, including the following:

Butts and hinges ANSI/BHMA A156.1 Bored and preassembled locks and latches ANSI/BHMA A156.2 Exit devices ANSI/BHMA A156.3 Door closers ANSI/BHMA A156.4 Auxiliary locks and associated products ANSI/BHMA A156.5 Architectural door trim ANSI/BHMA A156.6 Template hinge dimensions ANSI/BHMA A156.8 Cabinet hardware ANSI/BHMA A156.9 Power pedestrian doors ANSI/BHMA A156.10 Cabinet locks ANSI/BHMA A156.11 Interconnected locks ANSI/BHMA A156.12 Mortise locks and latches ANSI/BHMA A156.13 Sliding and folding door hardware ANSI/BHMA A156.14 Closer holder release devices ANSI/BHMA A156.15 Auxiliary hardware ANSI/BHMA A156.16 Hinges and pivots ANSI/BHMA A156.19 Strap and tee hinges and hasps ANSI/BHMA A156.20 Thresholds ANSI/BHMA A156.21 Electromagnetic locks ANSI/BHMA A156.23 Delayed egress locks ANSI/BHMA A156.24.

ANSI 156.2 includes provisions for locks to be Grade Certified. For a model to receive a grade, which ranges from 1 to 3, a sample lock must pass many rigorous tests that examine the lock's performance, strength, and durability.

Grade 1 locks are the strongest and are often specified for industrial applications. Grade 2 locks are for light commercial and residential uses. Grade 3 locks are the lightest and are primarily for residential applications. Some of the things the grading tests measure include bolt strength, turning torque needed to retract the latch, how well the finish holds up against salt sprays and other corrosives, and how many times the lock can be operated before failure.

Operational test:

The operational test examines the amount of torque needed to retract the latchbolt with and without a key. It's performed first by depressing the dead latch plunger (if necessary), then slowly applying torque force to the outside knob of an unlocked lockset until the latch is fully retracted. For a key-in-knob to receive a grade, torque used may not exceed 9 lbf-in. For a lever lock to be graded, torque cannot exceed 28 lbf-in. (Key-in-knobs are then tested in the opposite direction.) The test is repeated for the inside knob or lever.

The lock is then put in the locked position and the deadlatch plunger is again depressed (if applicable). Then the key is inserted into the keyway and is slowly rotated until the latch is fully retracted. Torque may not exceed 9 lbf in. The test is repeated in the opposite direction if the lockset is designed to allow such movement. If the inside knob or lever is key-operated, the test is also applied to the inside knob or lever.

Strength test:

The strength test examines how much forcible turning force a lock in the locked position can withstand. To be graded, a lock must stay locked after the minimum force has been applied. For a Grade 1, a key-in-knob must hold up to 300 lbf-in.; a lever lock must withstand 450 lbf-in. For a Grade 2, a key-in knob must hold up to 150 lbf-in.; a lever lock must hold up to 225 lbf-in. A Grade 3 requires a key-in-knob to withstand at least 120 lbf-in. and a lever lock to withstand at least 180 lbf-in.

Cycle test:

The cycle test examines how many times the lock can be operated before failure. For a Grade 1, a lock must complete 800,000 cycles. For a Grade 2, a lock must complete 400,000 cycles. Grade 3 locks complete at least 200,000 cycles.

+=+= Different types of keys have different parts.

Key Types:

There are six basic types of keys: bit, barrel, flat, corrugated, tubular lock, and cylinder. Although different types of keys have different parts, virtually all keys have a bow (rhymes with toe). The bow (or handle) is the part of the key that a person holds while inserting the key into a lock. Bows come in a variety of shapes and often have identifying information or advertising imprinted on them. +=+= some common types of keys. A bit (or skeleton) key is usually made of iron, brass, steel, or aluminum.

Major parts of the key include the bow, shank, shoulder, post, and bit. Many barrel keys look similar to bit keys, but barrel keys have a hollow shank and often don't have a shoulder.

A flat key is flat on both sides. Most are made of steel or nickel silver. Such keys are used for operating lever tumbler locks. Corrugated keys look similar to flat keys. Both types usually have the same parts. However, corrugated keys have corrugations (ripples) along the length of their blades. Corrugated keys are most often used to operate warded padlocks.

A tubular key has a short tubular blade with cuts (depressions) milled in a circle around the end of the blade. The key is used to operate tubular key locks.

Parts of a tubular key include the bow, blade, tumbler cuts, and nib. The nib is a small protrusion at the tip. It shows the position the key must be at to enter and operate the lock.

The most common type of key is the cylinder key. It's used for operating most pin tumbler and disc tumbler locks. Major parts of a cylinder key include the bow, shoulder (one or two), blade, keyway (or milling) grooves, and tip. The shoulders of a key are generally used as stops when cutting keys. When a cylinder key doesn't have a shoulder, its tip is used as the stop. The keyway grooves are millings along the length of the blade that allow the key to fit into a lock's keyway.

Key Blank Identification:

It's as important for locksmiths to be able to identify keys and key blanks as it’s for them to identify locks. A key blank is basically an uncut key. Before duplicating a key, a locksmith must find a matching blank.

Important factors to consider when choosing a blank to duplicate a bit key or barrel key are thickness of the bit and diameter of the shank and post.

Because there's usually a lot of tolerance in locks that use these types of keys, the blank might not have to match perfectly.

Important factors when choosing a blank for flat keys and corrugated keys are thickness, length, width, and shape of blade. The key and blank should match closely in those areas. A blank for a corrugated key should have the same corrugated configuration that the key has.

Choosing a blank for a tubular key is simple because there are few significant differences among tubular keys. The important areas of such keys are the size of the nib and the inside and outside diameters of the shank. If you find a blank that closely matches the key in those respects, you can duplicate the key.

Cylinder key blank identification:

The trickiest type of key to find a blank for is the cylinder key, the type that locksmiths are most often asked to duplicate. Three parts that are generally common to cylinder keys and their corresponding key blanks can be helpful when searching for a key blank. These are the bow, blade length, and keyway grooves.

The bow is the head of the key or blank. It's the part that you grip when using a key to operate a lock. Most cylinder lock manufacturers use distinctive key bows and many aftermarket key blanks copy their basic shapes. Based on the bow alone, a locksmith can often either quickly find a matching key blank or at least narrow the choices to a few key blanks.

The blade is the part of the key that enters a lock's keyway. Generally, the key and key blank should have blades of the same length. To compare lengths, you can either hold the key and blank together or use the illustrations in a key blank catalog. When using a catalog, lay the key over the illustration and align the shoulders. You can then observe the length at a glance because the key catalog drawings are the size of the original keys.

Keyway grooves (or millings) are critical. Only when the key and key blank have the same, or very similar, grooves can both fit into the same keyway.

One way to compare millings is to try to insert the key blank into the lock's keyway. If it can be inserted, the millings are the same or similar. You can also compare millings by holding the key and key blank side by side and looking at the blade tips. Finally, use the catalog to compare blade millings.

To use the catalog, stand the key directly over the cross section that appears under the blank's illustration. The grooves must match exactly to be considered the same.

Key manufacturers publish catalogs that identify their key blanks and sizes and show a cross section of each different blank. In addition, they may have a cross-reference section that refers to other manufacturers' keys that are com parable to each of the keys in that particular catalog. These cross-reference sections are valuable because they obviate reference to a wide variety of catalogs in order to determine the manufacturer of a given key blank. Merely refer to the key type and cross-reference it to the one that you have.

Some manufacturers have literally hundreds of key blanks and the cross reference section becomes unwieldy at times. It’s best to use a catalog that carries the most popular and commonly used blanks. About 97 percent of the keys you will duplicate will be in such catalogs. Other catalogs can be used for general reference but are not absolutely necessary to have for your shop.

+=+= Representative sampling of standard key blanks. (Taylor Lock Company)

+=+= Six-pin cylinder key and various associated keyways.

Keyway M is used only for the master key. (Taylor Lock Company)

+=+= A large master key system provides a great variety of key uses and control features through sub-masters and individual use of keys. (Taylor Lock Company)

Key Blank Examples:

On the following pages are illustrations of various types of cylinder key blanks. +=+= shows key blanks from the Taylor Lock Company. These blanks will fit a variety of American locks. Notice that in ++++ the blank is further laid out to incorporate a master key system and that, from the cross section, you can identify the various keyways that will fall into this particular master key system.

+=+= another keyway system with the applicable blanks.

Notice that within this key series there are three different key lengths, which allow for wider use of the master key system. The length also allows more pins to be used in the cylinders. This means a greater variety in the number of possible key combinations available to the system.

Foreign automobiles (and, naturally, their keys) are increasing in popularity, so it’s necessary to have a well-stocked variety of foreign lock keys in the locksmith shop. +=+=a variety of the more common key blanks in use. You should have these types and a slightly wider supply of other foreign auto key blanks available to service the needs of your customers.

+=+=Key blanks for foreign automobiles. (Taylor Lock Company)

Automotive Key Blanks:

Duplicating automotive keys is more prevalent in recreational areas and very large cities. Lost or stolen keys mean duplication and/or rekeying on a daily basis for many locksmiths. It’s imperative that, as a locksmith, you have in your shop an ample selection of automotive key blanks on hand. Keep a selection of the most common and popular automotive blanks in your van plus a few others that might be required. (Note: Every lock smith shop should have a standard selection of automotive key blanks, but in large cities and in recreational areas such as beaches, parks, etc., the need is greater than usual. Thus, the number and variety of blanks needed will be greater in these areas than in others. Always consult with your distributor or manufacturer's representative to obtain an accurate view of the types and quantities of blanks that you're likely to need; don't buy a larger selection than required just because you think you may someday need it.) +=+= is a list of foreign automotive blanks identified by the number and the vehicle they accompany. These are, by far, the most common vehicles for which you will be cutting keys. (This is a representational selection of popular keys that require frequent duplication; it’s not all inclusive.) Refer to your key catalog for illustrations of all the automotive keys and develop a working memory of them. After a period of time you should be able to look at a key that is already cut (or even a blank) and determine with relative accuracy its make of automobile and where the key blanks are located on your key blank board. +=+= shows some domes tic key blanks. +=+= lists the most common domestic keys by number of automotive type and shows a variety of foreign key blanks.

+=+=Foreign automobile key blanks.

+=+=Sampling of common domestic automobile key blanks.

Look-Alike Keys:

You will find key blanks that are look-alike keys-blanks made by a manufacturer other than the original with bows that look like the bows of the original key blanks. These provide you with a great advantage; as look-alikes, they are quickly identified with a specific lock manufacturer, enabling you to quickly select the proper key for duplication.

Because not all keys are look-alikes you will need comparison or cross-reference key charts-important reference tools. +=+= is a manufacturers' key comparison chart for automotive and house keys.

Suppose you have a customer who brings in two keys for duplication-one for her house and one for her car. The house key is National/Curtis number IN1 and the car key is 1127DP. As an up-and-coming locksmith, you carry a wide assortment of the most commonly used keys and you have a cross-reference key chart listing. You can quickly determine whether or not you have the particular blanks for these two keys.

Go to the cross-reference list and find that the IN1 goes to the Star blank 5IL1 (Ilco house lock). The 1127DP is an Ilco key for which you have the Star blank, HFD4-a Ford auto ignition key. Rapidly looking at the key blanks, you quickly select the two proper keys. Within minutes you have another satisfied customer, thanks to the cross-reference listing.

+=+= Domestic automobile key blanks.

+=+=Sampling of common foreign automobile key blanks.

The cross-reference listing is available from your key blank representative, or you can spend between $30 and $60 to get a complete cross-reference guide.

This is both an advantage and a disadvantage. With the full guide, you may have to look in a number of sections whereas with the smaller, individual cross-reference breakout from your key distributor/manufacturer, you are more likely to find the required key quickly.

+=+=Key comparison chart for automotive and residential key blanks.

A copy of a cross-reference listing is a prime requisite for every shop.

Remember, your priority is the listing obtained from your key manufacturer; you can get the guide later if you find you need it.

+=+= Neuter bow key blanks can be used for advertising purposes. Embossed logo; Custom incised logo; Standard incised design.

Neuter Bows:

Because most nonlocksmiths can only identify key blanks by their bows, locksmiths often use neuter (or security) bow key blanks to make keys harder to duplicate. Such bows have a generic shape and style and provide no information that identifies a lockmaker. That prevents unauthorized people who may have a key for a short time from running to any hardware or department store and getting the key copied. In addition to increasing security, such bows provide space to imprint advertising, increasing the likelihood that the customer will return to the same locksmith to get duplicate keys. +=+= neuter bow key blanks.