How to restore and sharpen an old file with citric acid

How to dilute citric acid to remove rust?

Remove rust from metal using citric acid

1. Degrease parts with detergent.
2. Pour heated water (up to 60 degrees) into a plastic container.
3. Dissolve the acid at the rate of 80 grams per 100 ml of liquid (concentrate).
4. Soak items for 3 to 20 hours (depending on the degree of damage).

25 Jan
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Indications for recovery

A file is a fairly simple tool, which is a steel rod with notches. Using such a cutting device, you can file the surface of metals and various other hard materials.

With frequent use, the working part of the file begins to become dull. This mainly happens when working with viscous materials such as copper, aluminum or stainless steel. During the processing process, metal particles flake off and get clogged into the opening between the notches.

The file must be restored if its working part begins to become dull

The clogged surface of the file shaft becomes smooth. It is difficult to work with such a tool. It slides on the surface and processing materials requires excessive effort.

Prolonged use of a non-working file can lead to its complete unsuitability. Therefore, at the first changes in the quality of the tool, it is recommended to restore its cutting part.

Prevention measures

To significantly extend the service life of a file, it is necessary to take into account some rules for its use:

1. The new tools have fairly sharp, but rather fragile teeth. Therefore, the file is not initially used for processing hard metals. It is worn in on the surface of softer materials - brass or bronze.
2. When working with a file, you should not use two of its cutting sides at once; the tool should always have a spare section with sharper teeth.
3. For surfaces treated with resins or greasy substances, an old file with worn teeth should initially be used. This will protect the new tool from rapid contamination.
4. Files must be stored separately. To prevent contact with other tools, it is recommended to wrap its cutting part in cardboard paper.
5. Before processing soft metals, the file is lubricated with chalk. This avoids frequent clogging of the teeth with small chips.

After each use of the file, use a brush to remove dirt on the shaft between the teeth.

Any old file can be restored. To do this, it is necessary to assess the condition of the tool, completely clean the working surface and select a convenient method for sharpening it.

Etching process

For etching, prepare a solution based on 50 g of citric acid and 1 liter of water. The latter must be clean, without chemical impurities. The acid granules are completely dissolved in the liquid, stirring the solution well.

If there is no acid, it can be replaced with table vinegar in approximately the same proportion or with ferric chloride in small quantities. The volume of water should be enough to completely cover the file.

The instrument is placed in a container with an acidic solution and is not removed for 24 hours. After 12 hours, evaluate the effectiveness of sharpening - wipe the file on a sponge and note the appearance of a dark coating on it.

The latter consists of particles of metal that have been chipped from the teeth of the file. Since the area of ​​these teeth is smaller than the total working area, the metal is removed from them somewhat faster.

Next, the needle file is again dipped into the solution and kept for another 12 hours, but the process is regularly monitored. If the file's condition has improved significantly, you can stop etching earlier.

Advice! The effectiveness of the procedure can be judged by the rate of formation of hydrogen bubbles on the file.

You can periodically clean the surface with a wire brush to speed up the process. Also, using a solution with a higher concentration of citric acid will allow you to get results faster.

The quality of tool sharpening is checked on an unnecessary metal or plastic part. Even a plastic lighter is suitable for this purpose. Run a file over the product several times and make sure that the gripping force has increased, and particles of the removed material are visible on the working part.

At the end of the work, the file is rinsed with water, treated with an alkaline detergent and washed again. This will help neutralize the citric acid and wash away any remaining impurities.

Neutralization of acid with an alkaline solution

Sharpening methods

The file can be returned to its working shape using chemical, mechanical, sandblasting and electrochemical methods. Each tool sharpening option requires a special approach and is used for specific purposes.

Chemical

One of the simplest and most effective methods for sharpening a file. Etching in chemical solutions allows you to completely restore the working surface of an old, dull instrument covered with rust.

Before treating a file with a chemical liquid, its surface is prepared:

1. All dirt is removed with a metal brush.
2. If there is rust, the instrument is treated with a special solution.
3. Then the cutting part of the tool is degreased. To do this, you can use any dishwashing detergent or washing powder.
4. The file, cleaned of grease deposits, is washed under running water. After this, it must be dipped in acetone to wash away any remaining oil deposits.

After such procedures, the rod with the teeth of the file will become completely clean and prepared for the etching process. For restoration, a special solution is used, the component composition of which has the following ratio:

• 86% - water;
• 8% - nitric acid;
• 6% - sulfuric acid.

The file is dipped into this mixture for ten minutes.
The chemical solution allows you to increase the height of the teeth on the cutting surface without changing the thickness of the tool. After the specified time, a check is performed on the work area. A file that is not sharpened well enough can be re-etched. The restored instrument is washed with soda solution.

Electrochemical

This method of sharpening a file also requires preliminary cleaning of its cutting surface from dirt and grease deposits. After this, the instrument is immersed in an acid mixture:

• 80% - water;
• 11% - sulfuric acid;
• 9% - nitric acid.

In this case, a low voltage direct current is passed through. Aluminum plates are used as cathodes, the area of ​​which must correspond to or slightly exceed the surface area of ​​the file - the anode.

Mechanical

This option for restoring a file involves replacing old notches with new teeth. The working part of the tool is pre-fired.

Heat treatment is performed in a special oven at a temperature of 760 - 820 degrees. After this, the old notch is removed on a milling machine and the surface is completely sanded.

New tooth cutting can be done manually using a chisel. Factories use special sawing equipment to produce the ribbed surface of the tool.

The final stage of mechanical restoration of a file is hardening. For this, a solution consisting of 50 liters of water, 2 kilograms of table salt and 1 liter of hydrochloric acid is used. After this, the tool is cleaned, washed in water with a small amount of lime to protect against corrosion and dried.

Sandblasting

For this method of file restoration, fine-grained sand is used. It is directed towards the cutting part of the tool at a slight angle. Sharpening is carried out from the shank side. Sand is passed under a pressure of 5 kgf/cm. sq. through a nozzle measuring 5 to 7 centimeters.

Sandblasting restoration method

The speed of sandblasting depends on the degree of flooding of the teeth and the grade of steel from which the file is made. The sand is directed towards the tool at a right angle. Initially, the main notches are sharpened, and then the surface of the auxiliary teeth is restored.

How to restore a file at home

Files and needle files become greasy and dull over time, and working with them becomes unpleasant and unproductive.
This especially happens when processing viscous materials with files - non-ferrous metals, copper, aluminum, stainless steel. Particles of these metals seem to be riveted onto the file, clog the space between the teeth and the file becomes 'smooth'. To restore such a file and return it to working shape, there is a simple method consisting of chemically etching the file in a special solution. Approximately the same technology is used to restore old, rusty files.

First, the file is inspected and, if necessary, cleaned with a metal brush to remove mechanical contamination. The files are then degreased in a solution of washing powder or dishwashing detergent, then washed with running water and then immersed in acetone. This removes all fat and oil deposits between the teeth from the files. You can also degrease a file by boiling it in a soda solution for 10 minutes.

If the file is rusty, it is immersed in a container filled with rust reducer. And keep it until the rust disappears. The rust reducer can be replaced with a 20% sulfuric acid solution.

The files are washed in running water and placed in a reducing solution consisting of

— Concentrated nitric acid — 8%

— Concentrated sulfuric acid — 6%

The peculiarity of this solution is that it etches the metal more in the recesses than on the protrusions. Those. it seems to deepen the depressions between the teeth of the file, and the teeth themselves are little etched. Thus, the height of the file teeth increases (although the overall thickness of the file decreases). And the file is thereby restored and becomes sharp.

The file etching time is approximately 5-10 minutes. After which the file is removed from the solution, washed and tested. If it is not sufficiently etched, the etching is continued.

After etching, the files are thoroughly washed in running water or soda solution to get rid of the acid.

Files should be preserved after restoration, since their surface is pure metal, which can very quickly become covered with rust. To do this, the files are dipped into machine oil (you can work them off), the oil is heated to a temperature of 100-120 degrees and held for 15-20 minutes.

After the preservation procedure, the files are removed from the oil, thoroughly wiped, dried and handles are attached to them.

In this way, files can be restored from almost any condition.

Under no circumstances should files be stored in bulk, in a general pile. At the same time, they rub against each other and become dull very quickly. Therefore, it will be better if you make a simple shelf for the files - a bookkeeper, where each file will have its own place and they will not touch each other. And the files will be visible - you won’t have to go through them all to choose the one you need.

Material for the shelf - plywood, thin board, plastic.

Handles for files.

If you buy files that do not come with handles, you will have to make them yourself.

Good handles for needle files are made from wine corks. The needle file is stuck into them without preliminary drilling.

Handles for more powerful files can be made from short sections sawn from shovel cuttings. They can be bought at hardware stores and are not expensive. A large chamfer is removed from the ends of the handle, and the wood is sanded. A hole with a diameter slightly smaller than the file shank is drilled at the end of the cutting segment and the file is driven into the handle with tension. This way you can provide handles for all files.

Another good starting material for file handles is thick branches produced when pruning trees in the spring. Peeled of bark and dried, such handles not only look beautiful, but often have a very comfortable “pistol” curve.

What is a file?

A file is a metal rod with a notch, a multi-edged tool. The file is designed for processing various materials: metal, wood, plastics and other materials.

Files are classified according to the frequency of cuts:

1. Personal - from 13 to 25 teeth per 1 square centimeter. Designed for fine, finishing work, in which a layer of up to 0.025 mm can be removed;
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2. Bruiser files are files with a sparse arrangement of teeth, from 5 to 13 pieces per 1 square centimeter. Such files are designed for coarse sawdust, the thickness of the removed layer is 0.1-0.15 mm;

3. Velvet files are for fine work, the thickness of the removed layer is 0.01-0.0025 mm. On the surface of the instrument there are from 25 to 80 notches per 1 square centimeter.

4. A needle file is a small file for very fine work;
5. Riffle is the same needle file, but with a curved working part, mainly used in jewelry.

Restoring a file using folk methods

At home, you can sharpen a file using simpler methods. Many craftsmen use improvised means to restore the cutting part of the tool:

1. Lemon acid. Dirt and greasy deposits are removed from the file. After this, a solution is prepared - two full teaspoons of citric acid per glass of clean water. The file is placed in an acid solution for a day. In this case, you should periodically check the condition of the tool. After restoration, the file must be washed in an alkali solution to neutralize the acid.
2. Ferric chloride. The reagent is mixed with water in a ratio of 1:4. The prepared file is immersed in this solution for 1.5 hours. After this treatment, the tool becomes much sharper.

Ferric chloride - a means for restoring a file
Instead of citric acid, you can use vinegar to restore a file. A simple soda solution is successfully used to degrease the surface. The instrument should be boiled in it for 10 minutes.

Preparatory activities

First, they check the quality of the tool’s work - assess whether it is so dull. If the file slips over the surface when moving, it definitely requires sharpening.

Important! The working part is cleaned of grease, oil deposits and other contaminants using a metal brush. This will allow you to sharpen it better later.

Next, the instrument is degreased. It is placed over an elongated cuvette, the cleaning composition is sprinkled on top of the blade and the entire surface is thoroughly cleaned with a toothbrush.

Then the device is washed directly under the tap to wash off any remaining product. If water does not collect on the metal and does not roll into balls, but covers it with a continuous layer, degreasing has been carried out efficiently.

Features of chemical restoration of instruments

The simplest and long-known way to restore the ability of a file to work effectively is chemical. It has been known for about a century. For such processing, it is necessary to apply a special etching solution to the instrument. Under its influence, the edges of the notches on the surface being treated dissolve. In this case, the edges of the edges are not affected, since hydrogen bubbles adhere to them, which protect them.

Gradually, under the influence of the etching composition, the edges become sharper. After some time, the hydrogen bubbles will increase so much that under the action of the buoyant force of the liquid they will come off the surface being treated. At this time, it is necessary to stop exposure to the etching solution. In some cases, it is possible to sharpen a file in this way more than once.

Files and needle files can be sharpened using various etching compounds. Most often, solutions of sulfuric and nitric acid are used for this purpose; hydrochloric acid is also used in undiluted form. The work must be done in special containers. Plexiglass baths are best suited for these purposes. The height of such containers should be slightly greater than the length of the working part of the tool. In such baths, files and needle files are cleaned of rust and etched. For other types of processing, you can use tall enamel bowls, cans or porcelain glasses.

In addition to special containers, you also need to stock up on wire brushes. Chemical restoration is suitable for tools with worn teeth, but it will not be possible to restore the functionality of files with chipped teeth or completely beveled. Tools with different notch sizes need to be processed separately. Sorting must be done before processing. Wire brushes are needed to prepare for etching. You need to clean the tools with brushes, moving them along the notches.

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