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To File Flat


From American Horologist magazine, October 1938

To File Flat

By W. H. SAMELIUS, Chairman, National Technical Board

To FILE flat and have the file marks look as if the piece worked upon had been brushed, is an art acquired only by practice. Clock work requires sometimes the use of a file on large pieces, but watches for repairs seldom call for any large pieces; but the principle of filing is to be learned by beginning on large work. A visit to any large machine shop and noting the operations of expert filers will give better ideas of the manner of holding and operating a file.

Good practice would be obtained by making a lathe something after the pattern of the ordinary brass Swiss lathe, and even if unsuccessful in making a lathe adapted to watch work, it could be used for polishing. Take your casting as it comes from the brass foundry and screw it firmly in the vise, standing up before your work,· holding the file by the handle in the right hand and guiding the end with your left; hold it flat and push forward with some vigor.

Keep it flat by feeling, and note the cut it makes. Lift it entirely off the piece you are working on when you draw back, and note the effect, which will enable you to adjust your hands so as to make the next stroke more correctly. Be careful to avoid an oval motion. The tapering shape of many large files is such that by simply pressing the file down on your work you can give it just the shape of the taper of the file; but this is to be avoided, and only practice will teach how it can be done. The eye must be frequently called in use, so as to have sides parallel and corners square. After all the casting marks are removed and the article has been shaped and reduced to proper size, a smoother-cut file is used to remove the coarser file marks and get nearer to size. When this is completedcare being constantly exercised to keep the file marks running in one uniform direction-use a flat piece of Scotch stone with water to remove the file marks, after which a flat buff with tripoli.

Cocks and watch bridges are generally turned out with a lathe, and finished flat by machinery, although we have seen some very nicely filed out and polished.

The peculiar matted appearance is produced by acids; and when plates were fire gilted, before the application of electro gilding, the process of fire gilding increased this matted appearance.
Having learned the knack of flat filing, to reduce the practice to small work a good plan will be to put such small pieces as clicks, ratchets, ratchet plates, etc., on a small white pine or basswood block, and by pressure imbed them in the wood. Sometimes a few pins made with the pin vise, drawn around the edges pretty deep into the block, greatly aid; and some articles can be better handled by holding in the fingers and passing the file over. To remove file marks from steel, use oil stone, either in slips or by rubbing on a large flat stone. Much depends on the piece you have to work upon. 1 In these days when all kinds of material is so abundant, it is not often necessary to make a new piece from a steel wire or bar, but if you find a piece of steel material that will nearly answer, don't undertake to complete the fit by filing until you have drawn the temper; it will cost you less for files, broaches, etc., to do this, and besides save time.

To be sure you will have to re-harden, temper and finish, for you can't get a nice polish on soft steel.  After you have the knack of carrying the files so as to do flat work, it will not be necessary to stand; but for anything large the standing position is always to be preferred; there is something in the swaying motion of the body when standing that enables you to execute better work, and on small work you can bring the principle to bear when sitting at the bench. 

A mechanical eye is almost an absolute necessity for a watch repairer. vVhenever you have a piece to make it should be made so that if the man who made tbe watch was to examine it he could not detect the piece replaced unless by superior excellence. All the botch III akers of the trade have no idea of finish-their only idea is put in something that will work, no matter how unsightly. 

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