Impressioning Manual for Amateur Locksmiths

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2024-11-19 1 0 69.22KB 10 页 5.9玖币

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1.0. INTRODUCTION

1.1. Impressioning is a method of fitting a key to a lock without taking the lock apart.

Basically, here is how it works: A key blank is inserted into the lock, then turned to bind the pins.

When the pins are binding, the key is wiggled or moved to produce marks on the blank. If a pin

is at the shear line it will not bind, and no marking will occur. When marks are found, the places

on the blank which have marks are then filed. The marking and filing process is repeated as

necessary to produce a working key which raises all the pins to the shear line, thus opening the

lock. Although impressioning is not hard to learn, it does take some practice to develop the skill.

Of course, the more you practice, the easier it gets!

1.2. How long does it take to impression a key? With practice and by making use of shortcuts,

it is not unusual to be able to make a key in about 10 minutes. Some locks will take longer.

Sometimes as little as 5 minutes is possible if you are both lucky and skilled. If you try to pick a

lock, you don't know in advance if it will take one minute or thirty. With impressioning, opening a

lock is a more reliable and predictable process.

2.0. PRACTICE LOCKS

2.1. You can start out with any lock, but I will suggest starting with an average sized four-pin

Master padlock. They are easy to impression, and blanks can be easily obtained at a hardware

store. You should get more than one blank for practicing. Five is probably a reasonable number.

2.2. Below are some depth and spacing data for the Master padlock, which as you will see

later, can be useful (although not necessary). The depths are measured from the bottom of the

blade of the key, up to the bottom of the cut where a pin will rest.

Cut # Depth Cut # Depth

0 .280" 4 .220"

1 .265" 5 .205"

2 .250" 6 .190"

3 .235" 7 .175"

The distance from the shoulder of the key to the first pin is .185", and the spacing between

pins is .125" (you really don't need these last two numbers, but they may be helpful references

as you are first learning to recognize what the marks look like).

2.3. Another good approach to using a practice lock is similar to that sometimes

recommended for learning picking: Get a lock cylinder and remove all the pin stacks but one.

After you have impressioned the one pin lock, add another pin stack and try again. Continue

adding pin stacks until you can impression the whole lock.

3.0. FILES

3.1. Six inch, #4 Swiss-cut round or pippin files are normally used for impressioning (the files

are called 6", but are actually about 8" long including the tang). Both types of files taper down to

a smaller cross- sectional size towards the tip. The round file is usually used in conjunction with a

small flat or triangular file which is used to shape the flat sides of the cuts on a key. The pippin

file has sort of a teardrop cross section, rounded on one side, and with two flat surfaces meeting

at a knife edge on the other side. The flat surfaces are used like the flat file above to shape the

sides of cuts.

Chances are that you won't find these kind of files in your local hardware store, just because

they have finer teeth that are required for most purposes. Locksmith suppliers carry them, of

course. You can also get them through a machinist's or jeweler's supply house.

3.2. The particular #4 Swiss-cut pattern is used for impressioning work because it leaves a

very fine, slightly dull, and slightly corrugated surface on the blank, which permits visible marks

to be made by the pins rubbing on the blank with very little pressure. A few locksmiths use a #2

Swiss cut pattern because it cuts faster, but most authors specify the #4. Having tried both

types, I strongly recommend the #4 also.

3.3. It is also a good idea to get a handle for the file, as it permits better and more

comfortable control of the file. A file card is a special brush made to clean the teeth of a file. The

soft brass of the key blanks tends to clog up the teeth on an impressioning file a little bit, which

affects the quality of the fine surface you are trying to produce on the blank. Don't be cheap - get

a file card too.

3.4. A few tips on using files: Files cut only on the forward stroke. So, push the file slowly and

evenly forward with gentle cutting pressure, and draw back the file without any cutting pressure.

Particularly when impressioning, do not apply pressure when drawing back the file, as it tends to

polish the surface of the blank (a dull surface is needed when impressioning). Hold the file with

an extended index finger pushing down on the top edge of the file to control cutting pressure.

Light cutting pressure will produce the finest finish for producing visible marks. Use heavier

pressure to remove material rapidly, followed by lighter strokes to finish the surface for marking.

4.0. BLANKS

4.1. Soft brass blanks are the best for impressioning. Steel blanks are much harder than is

desirable, and aluminum blanks develop fatigue cracks easily when using hard turning tension. If

you can only find bright plated brass blanks, you will have to file the plating off the top of the

blade with your impressioning file. Only file deep enough to remove the plating, because with

some locks a #0 cut requires the full un-cut height of the blade. With the plain brass blanks, you

also need to smooth the top of the blade with your impressioning file in order to leave a surface

that will show marks - just be careful not to take off too much.

note: Some lock manufacturers use #0 and others use #1 to indicate the highest depth cut.

For consistency, #0 will be used in this manual when referring to the highest depth cut (unless

otherwise noted), which is equal to or very close to the full un-cut height of the blade of the key

blank. A #1 cut refers to a cut which is one step lower than the un-cut height of the blank.

4.2. Some people like to prepare the blanks by either thinning them down in width with a flat

file, or knife edging the top of the blade. In both cases the idea is that a very thin piece of metal

can more easily be deformed than a thick one. In the case of thinning down the blade, it can also

be wiggled around more in the keyway. When thinning a blade, do not thin the area immediately

adjacent to the shoulder of the blank where the blade enters the keyway. You will be applying

hard turning tension on the blank later and it is important not to weaken it at the point where

most of the turning stress is applied.

Knife edging is used more often when the pull-out method (more about this method below in

section 5.5.) of obtaining marks is to be used. Knife edging is used to thin only the top of the

blade to make the initial marks more visible. To knife edge the blade, file both sides of the top

the blade at about a 45 degree angle. The idea is not to make it really sharp like a knife, just to

make the edge weak enough to mark more easily on the top surface.

4.3. As an example of the utility of knife edging or thinning, I took a new blank for a Master

padlock and prepared the flat top surface of the blade with my impressioning file. After some

wiggling, I could see one mark at the tip of the blade, which is enough to start with. But, I then

knife edged the blade and wiggled some more. This time I could easily see marks from all four

pins. With the knife edging, less wiggling was required and the marks were much more visible.

5.0. MAKING THE MARKS

5.1. There are three commonly used methods for making the marks. They are called wiggling,

tapping, and pulling. In each of the methods, the blank is inserted in the keyway, then turned

hard to bind the pins. Usually turning pressure is applied in the direction you want the lock to

open, but you can try both directions to see which leaves better marks. It is important to make

sure that the blank is evenly seated on the bottom of the keyway before applying turning

pressure. If you are holding it tilted, some of the pins will already be pushed up and won't leave

any marks.

5.2. When impressioning, you will need something to hold the blank because of the repeated

hard turning tension used (the tension is harder than is used for picking, but not hard enough to

break the blank). A small pair of vice-grips (no larger than the 5" size) works well. Attach the

vice-grips like a handle, aligned with the long the axis of the key blade (not at a right angle like a

turning wrench). There are also some commercially made handles for impressioning. There is at

least one with a trigger handle to help pull out the blank uniformly each time, when using the

pull-out method.

5.3. Wiggling is accomplished by applying turning tension, then wiggling the blank up and

down causing the top of the blank to rub against the tips of the bound lower pins.

5.4. Tapping is a variation of wiggling. The blank is inserted into the keyway, then a steel rod

is placed in the hole in the bow (handle) of the key to provide turning tension. A small mallet is

used to tap on the bow to make the impressions. Tapping on the top of the bow pushes up the

tip of the key by lever action, and tapping on the bottom of the bow pushes up the back of the

key by direct action.

5.5. The pull-out method only works after you have cut down to at least a #1 depth, hence

the popularity of knife edging the blank, then using the wiggle method to see if there are any #0

cuts to start with. To use the pull-out method, apply turning tension, then pull out on the blank

(don't try this method on disk or wafer locks, because the disks may bend or break). Unlike the

wiggle and tapping methods, the marks produced by pulling will not be exactly where the pins

are, the distance away being related to how far you pull the blank out (maybe 1/16"). For this

reason it is helpful to scribe lines down the side of the blank after the pin locations are found by

the wiggle method, to use as a reference when filing. The advantage of the pull-out method is

that it can leave more easily visible marks than the previously mentioned methods.

5.6. There is more than one way to implement the pull-out method. One technique involves

attaching a C-clamp to the bow, then using the C- clamp to provide turning tension on the blank.

A screwdriver is placed between the side of the bottom end of the C-clamp and the face of the

lock, then the screwdriver is twisted to pry the C-clamp (and therefore the blank) in a direction

out from the face of the lock (no more than about 1/16").

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ImpressioningManualforAmateurLocksmiths1.0.INTRODUCTION1.1.Impressioningisamethodoffittingakeytoaloc...

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