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HAND TOOL

 

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Files come in a wide variety of materials, sizes, shapes, cuts, and tooth configurations. The cross-section of a file can be flat, round, half-round, triangular, square, knife edge or of a more

specialized shape. There is no unitary international standard for file nomenclature; however,

there are many generally accepted names for certain kinds of files.

The cut of the file refers to how fine its teeth are. They are defined as (from roughest tosmoothest): rough, middle, bastard, second cut, smooth, and dead smooth. A single-cut file has

one set of parallel teeth while a cross-cut or double-cut file has a second set of cuts

formingdiamond teeth .[1] In Swiss-pattern files the teeth are cut at a shallower angle, and are

graded by number, with a number 1 file being coarser than a number 2, etc. Most files have teethon all faces, but some specialty flat files have teeth only on the face or only on the edge, so that

the user can come right up to another edge without damaging the finish on it.

The files pictured on the left are designed for use in a filing machine.

A filing machine is similar in appearance to a scroll saw or  bandsaw in that the file is mounted

vertically in the middle of a table. When in operation the file reciprocates vertically while theworkpiece is presented to the file's face and manipulated around the table/file as the shape

requires.

The cone point of the pictured, top two files allows the files to center themselves firmly in the

 bottom file holder. The pictured, lower two files are required to be inserted into the bottom fileholder and physically restrained with set screws, an identical process as for the top holder.

Filing machines are useful tools as they reduce fatigue and improve product accuracy, and

although not usually seen in modern production environments, they may be found in older 

toolrooms or diemaking shops as an aid in the manufacture of specialist tooling.

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Teeth

Files can be categorised into three tooth types:

Single cut - the file has a single row of teeth, making for smooth cuts

Double cut - two rows of teeth arranged at an angle to each other; most files are like this

Rasp cut – raised teeth used for cutting soft materials, eg wood

Furthermore, the coarseness of files can be classified (in order from most coarse to least coarse)

as: rough, coarse, bastard, second-cut, smooth, dead-smooth, super smooth.

Selecting a File for the Job

It’s very unlikely that you are going to have 20 different files sitting in your tool-box, ready to

go. So most of you are not going to say to yourselves: “Hmm, will I use a second-cut half-round

on this or a single cut mill file?” Instead, you’re going to grab the file that looks most suitable – even if it really isn’t!

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When selecting a file, the most important things to get right are the teeth coarseness and the file

shape.

A file that is too coarse will (1) make very deep scratches which will be later hard to remove, (2) potentially jam on the surface, breaking teeth and (3) potentially take off too much material – a

disaster, because you can’t put it back! For these reasons it is better to select a file with teeth thatare too fine rather than too coarse. The worse thing that can then happen is that it will take you

longer to do the job.

The softer the material, the coarser the file you can use – but the quicker material will be

removed. A coarse file used on soft plastic can remove a few millimetreseach stroke – it takes

very little filing before you find that you’ve gone too far.Therefore,be conservative in the

coarseness selection, leaning towards files too fine rather than too coarse.

While tooth coarseness is usually judged just on the appearance of the file (ie teeth per inch), in

the case of worn files, the smoothness of the cut may be quite different to the file’s appearance.

For example, a coarse file with all the edges worn off may in fact act as a smooth file. Therefore,it pays to know your own files and mentally pigeon-hole them according to their actual

 performance.

The file shape is critical. When filing a large flat surface, pick the widest file you have available.

When enlarging a hole, pick the largest round file that will fit through the hole. In both cases, asmaller file will be much harder to accurately control.

If you are using a half-round file to enlarge a hole, make sure that the file isn’t too large – the

edges will dig in and the hole will become ragged.

In all cases, before you start to remove material, run the file gently over the work so you can seewhere material will be removed. This ‘try before you file’ approach will allow you to quickly seeif the teeth on the edge of a file will unexpectedly take away material, or if the file is too large or 

too small.

• Always have a handle fitted to a file. Not only is the file then much safer to use but it willalso give you better control.

•  Never use a file as a lever or pry bar. The hardened steel is brittle and will snap.

• Files are best stored apart so that their teeth are not touching.

• In hot, wet environments, files can rust. To stop this occurring, give them a wipe over 

with a thin coating of engine oil.

• If they are cheap enough, secondhand files are always worth buying. Even worn files can be used as final-finish tools.

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File Cards

Files that are used on soft materials (egaluminium or copper) tend to clog. The tiny metal chips

caught in the file teeth reduce the cutting efficiency of the file and can also cause severescratching of the surface. A file card (a bristle brush) can be used to clean the teeth. I simply use

a wire brush.

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File Shape

The most common file is a flat file. A flat file has cutting faces that are parallel to one another.

In plan form the file is normally slightly tapered and has cutting teeth on both edges. The mainteeth are normally arranged in a double row. This type of file is a general purpose design suitablefor reducing to size and shape or fit finishing.

A mill file is similar to a flat file but it is thinner and smaller. Its size allows it to be used where a

flat file cannot – for example, filling a slot. Mill files generally have only one row of teeth (see

 below for more on teeth rows).

A hand file is like a flat file but it has teeth on only one edge. This characteristic is veryimportant as it allows the filing of a shoulder or internal edge of a square or rectangular cut-out

without inadvertently filing away the other surface. If you absorb only one thing from this story,

it’s this point: that some flat files don’t have teeth on their edges!

A round file (called a ‘rats tail’ if the diameter is very small) is a very useful file. It is used for enlarging or elongating holes or for filing the inner diameter of tightly curved surfaces.

Another very useful file is the half-round. This is useful for enlarging big diameter holes or for 

filing gentle curves. Because one face is flat and the other rounded, it’s a file that can be used a

great deal – one side for normal filing and then without having to put it down and pick upanother file, the other side immediately available for filing curves.

A square file has equal widths on each cutting face – it is square in cross-section but tapers

down in size towards the end. This type of file is useful for enlarging square and rectangular cut-outs. In my home workshop I rarely use this file.

A triangular file is also used relatively rarely. Because it has teeth on all surfaces (including the

corners) it is a very easy file to make a mistake with – to elongate a corner when using it to file a

square opening, for example. However, when a triangular cut needs to be made in a surface (for example, to get a round file started, so creating a half-round opening) it works well. A triangular 

file can also be used for restoring threads and gear teeth.

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Filing Techniques

Filing’s filing, eh? What’s there to know? In fact, there are three different types of filing

techniques.

Heavy Filing

Heavy filing is used to remove a lot of material. One hand holds the file handle and the other firmly grasps the other end. The file is moved back and forth across the work, with more

 pressure being used on the ‘push’ stroke than the return. A relatively coarse file is used.

When it’s possible, mark a line that you’re filing towards - and always stop well before the line.

When heavy filing a flat surface, it’s very easy to round the edges as the file ‘rocks’ over thework. Therefore consciously try to keep your arms moving back and forth in a perfectly flat

motion, and frequently check the flatness of the resulting surface with a steel rule or square.

Where the work is able to be mounted in a vice it should be near the height of your elbow asyou’re standing erect – stooping over the work will make it harder to keep the file moving in the

correct plane.

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Light Filing

Light filing is used for shallow cuts and when your cutting is approaching the marked line. Onehand holds the file handle as before, but the other hand holds the end of the file in just the finger 

tips. The pressure used in light filing is much less than for heavy filing. A finer file is used and

this – and the lighter pressure – results in much less material being removed each stroke.

Light filing can be used to ‘true’ the surface and/or take off just a tiny amount of material.

Draw Filing

Draw filing is when the file is moved over the item with a sideways action. It is a good technique

for removing scratches left by the other filing techniques and can be used to polish the surface. Itis also good for fixing square edges that have been rounded by inadvertent rocking of the file.

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PinningA method of bone fixation, usually for treatment of fractures, in which metal pins are placedwithin the medullary cavity or anchored in bone. Two types of pin in common use are Steinmann

and Rush.

Ways to avoid pinning

• Keep the workshop clean and tidy at all times;• Always seek instruction before using an unfamiliar piece of equipment;

• Only use tools and machines for their intended purpose;

• Report all damaged equipment and do not use it until it has been repaired by a qualified person;

• Where machine guards are provide they must be kept in place;

•  Never distract the attention of another staff member when that person is operatingequipment and never indulge in horseplay;

• Always use the appropriate personal protective devices and check that they are clean andin good repair before and after use;

• Long hair needs to be restrained by either a tie or hat;

•  Never use compressed air for cleaning clothing and machinery;

• Report all hazards and unsafe conditions and work practices.

SAFETY PROCEDURES

An appropriate file used carefully can result in accurate and clean work - but it’s nearly as easy

to end up with work pieces that are ruined! When using files remember these two key points:

• Pick the right file for the job

• Use it slowly and carefully, changing techniques as the job progresses to its finished state