Fundamentals Of Filing (1942)

of all hand tools used in machine shop work perhaps none is more important than the hand file anyone doing filing must learn the many kinds and sizes of files since the correct file must be selected for each job the worker is removing a sharp and dangerous age he is applying just enough pressure on the forward stroke only to make the file cut the fingers are held away from the sharp edges the efficient worker always uses an easy long stroke the single cut file teeth are cut at an angle to the edges of the file and contact the work at approximately 90 degrees in order to get a smooth finish due to the fact that a file is cut the same on both sides the teeth run in the opposite direction when observed from the top side or operators viewpoint the workman has been using a single cut bastard cut file the word cut as used here refers to the spacing between the teeth the coarseness or finest of these spacings determines the coarseness or fineness of cut on all files under extreme magnification the teeth on single cut files resemble the teeth of a hacksaw let us compare a medium cut file with the bastard cut they are both single cut the difference lies in the spacing of the teeth all series of cuts can be roughly classified as coarse medium and fine however the bastard cut is between the medium and fine cuts in all series of files here is a typical filing job a piece of cold-rolled steel cut off with a hacksaw to be filed the metal is soft and requires very little filing so a single cut medium cut file will be used before starting to file a flat surface be sure the surface is square the skilled workman knows the importance of the right file for the right job a single cut medium cut file is selected this file properly used will leave a smooth surface that can be easily finished be sure the file is straight filing a true flat surface requires a straight file all files remove metals in the form of small chips a magnified slow-motion view shows the formation of these chips some chips cling to the file and may be removed by tapping the file on wood every few strokes for an illustration let us examine a file that has been improperly used if the chips are not cleaned from the file they will pack between the teeth forming pins these pins scratch the surface of the work with this result tapping the file on wood does not always knock out the chips therefore a file card should be used frequently if the pins cannot be removed by carding a piece of soft metal may be used the expert workman uses only enough pressure on the file to make it cut very fine thin oil kerosene or chalk on the file will help keep the chips from sticking when filing soft metals breaking the corners and cleaning the work is necessary for the next step in the filing operation to produce a smoother surface the worker selects a finer single cut second cut file using a file in this manner is called drawer filing after the surface has been made smooth it can be polished by using a very fine single cut file drawer filing is used for all finishing and polishing here is a comparison of the single cut second cut file used in the first drawer filing with that of the finer single cut file used in the final polishing the workmen runs his hand over the file to make sure that it is free of chips chalking the file helps prevent pinning and gives a finer polish lastly the work is checked for accuracy such smooth and accurate surfaces are achieved by the workman after much practice and development of his skill plus his knowledge of files and the ability to select the right file for the right job we have been studying the single cut file in several degrees of coarseness and finest now let's examine the double cut file required by this job let us compare them under extreme magnification the double cut file is contrasted with the single cut file has two cuts forming a diamond pattern of pointed teeth the single cut as parallel rows of teeth a double cut file is always selected to remove excess metal with a free easy full stroke just enough pressure is used to make the file cut too much pressure may damage the work as well as ruin a file by breaking off the tips of the teeth a file can be ruined on the first stroke by too much pressure in this case the worker is filing a flat on the tough cast iron ring and has selected a double cut file since excess metal is to be removed and there is no need for a smooth finish also when filing soft metals such as aluminum a double-cut file is selected to remove excess material however there are special files for this type of work such as the shear cut file the teeth on the shear cut file run at a sharp angle to the edge of the file here the worker is filing excess metal from brass another soft metal he has selected a coarse cut double cut file let us compare the double cut medium cut file and the bastard cut the bastard cut is perhaps the most universal of all cuts the course cut double cut leaves this surface a finer finish is given with a single cut file polishing is done by draw filing with a single cut file and files are made in all shapes and sizes in all degrees of kindness and coarseness and for all different kinds of metal there is a file for every job wherever there are metal parts to be filed by hand to remove excess metal to provide smooth surfaces or to shape those parts just remember select the right file for the right job use fine cut files for hard metals use coarse cut files on soft metals use double cut files or special files to remove excess metals use single cut files for a smooth surface use only single cut files for drawer filing keep the file clean use just the right pressure on the forward movement only and a long easy stroke to do the jobs that files are made to do in the hands of craftsman