How to sharpen an ax or a knife, almost everyone knows. Much more complicated is the case with old files. Recovering a file that has become dull is not so easy, and very few masters know how to do it. Often, old tools are simply thrown away.
File types: a - flat flat blunt-nosed; b - round; in - semicircular, g - square; d - trihedral; e - flat sharp-nosed; g - hacksaw; h - oval; and - lens; k - rhombic; l - semicircular wide; g - rasps, n - for filing machines; o - for soft metals, as well as curved files.
There are several ways to sharpen a file:
Features of chemical recovery tools
The most simple and well-known way to restore the ability to work effectively files - chemical. He has been known for about a century. For such treatment, it is necessary to apply a special pickling solution to the instrument. Under its influence, the edges of the notches on the treated surface dissolve. At the same time, the edges of the faces are not affected, since hydrogen bubbles stick to them, which protect them.
Gradually, under the influence of the etching composition, the edges are sharpened. After some time, the bubbles of hydrogen will increase to such an extent that under the action of the buoyancy force, the liquids will detach from the surface being treated. At this time it is necessary to stop the effect of the pickling solution. To grind a file in this way in some cases it is possible repeatedly.
Sharpen files and files can be a variety of pickling compounds. Most often for this purpose solutions of sulfuric and nitric acid are used, hydrochloric acid is used undiluted. The work must be done in a special dish. It is best suited for these purposes baths made of organic glass. The height of such containers should be slightly larger than the length of the working part of the tool. In these trays, files and files are cleaned of rust and etched. For other types of processing, you can use high enameled bowls, cans or porcelain cups.
In addition to special tanks, it is also necessary to stock up with wire brushes. Restoration by chemical means is suitable for tools with worn teeth, but it will not be possible to restore the capacity of files with crumbled teeth or completely mowed. Need to separately handle tools with different sizes of notches. Before processing, you need to sort. Wire brushes are needed to prepare for etching. It is necessary to clean the tools with brushes, leading them along the notches.Back to table of contents
If there is rust on the metal surface, then you will need to place the tools in concentrated hydrochloric acid. The rust removal procedure lasts from 30 minutes to 1 hour and is carried out exclusively in a fume hood. After removing rust from metal surfaces, degrease the tool. To do this, it is immersed in a 10% soda solution with a temperature of 60 ° C for 10-15 minutes. after that go directly to the etching.
The solution is prepared in advance.
During the preparation of the solution it is necessary to add acid to water, and not vice versa.
Scraping the sawed surface with a file with a sandpaper (paper or cloth): a - abrasive cloth, b - file with sandpaper and work with it, cleaning the concave surface, d - finishing with circular strokes.
The acid should be poured in a thin stream, and the solution at the same time constantly need to stir. A 68.7% solution of sulfuric acid (with a density of 1.6 g / cm3) and a solution with 47.5% nitric acid (with a density of 1.3 g / cm3) must be prepared. You can improve the etching process if you add iron nails to a solution of nitric acid. It is better to use large nails so that the reaction does not proceed too violently. This must be done in a fume hood. You will need to take 40 g of nails per 1 liter of solution.
The solution is prepared immediately before you place the files there. Acid and water should be at room temperature. The entire etching process must take place in a fume hood. Files should be lowered into a container with a solution in a vertical position. It is necessary to ensure that the entire working surface is covered with liquid. It is necessary to underfill the liquid to at least 3 mm to the edge of the container. This is necessary due to the fact that sometimes the solution may foam.
The duration of etching depends on many different factors. It is impossible to determine exactly what time is required. It is necessary to take a sample after 5 minutes after immersing the instruments in liquid. To do this, remove 1 file and rinse it with water. It is necessary to rest the file on the table with the end and firmly hold the handle in your left hand. The right hand on the work surface superimposed plate of metal, which is processed with this file.
The scheme of sharpening the adjacent teeth of the day of using the hacksaw blade with broken teeth.
When the metal plate moves along the notches of the file, the tool should cling to the surface with the teeth. If it slips, then recovery has not happened yet. Subsequent tests are performed every 3 minutes. After the restoration of the sharpness of the files they are removed from the tank, washed and cleaned of sludge - black plaque.
Completing the restoration of the health tools by immersion in a neutralizing solution, and then - in a passivating. To neutralize the reaction on the surface of the metal is used soda solution, prepared for degreasing the surface. Tools are immersed in it for 5-10 minutes. To prepare a passivating solution, you will need laundry soap (5 g) and sodium nitrate (1 g) dissolved in 1 liter of water. The solution should be heated to a temperature of 70-80 ° C. The files are immersed in it for 5-10 minutes. This will prevent rust on them. After this, the files are placed vertically in a container and allowed to dry.
Thus, you can clean the file and make it as effective as a new one in several ways. Chemical sharpening is the easiest and most affordable of them; for the rest, specialized expensive equipment is required. As a result, after chemical recovery, files work no worse than new ones. So, you can save on the acquisition of a new tool substantial funds.