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Metal Files - Sharpening And Maintenance Tips

Metal Files - Sharpening And Maintenance Tips

Although they don't garner as much attention as chisels and planes, files are also cutting tools that perform best when they are sharp.

Sharpening Metal Cutting Tool Files

Acid is the easiest technique to sharpen files since they are constructed of high-carbon steel that has been hardened and has many tiny teeth. Use a drain cleaner (sulfuric acid) and vinegar (acetic acid). Metal is removed from the surface by the acids' reaction with the iron in steel. Wear rounds off a dull cutting edge, and the radius of the curve gets smaller and the edge sharpens as the metal dissolves. The file must be cleaned up before applying acid. The acid cannot reach the metal if something is lodged between the teeth. A file card with its short, firm wire bristles will perform a better job of clearing away the debris left by the task than a wire brush.

Paint, epoxy, and aluminum are usually the culprits when the debris is stuck hard in the gullets between teeth. To remove such debris, you can use a piece of brass or copper tubing with one end flattened. The copper or brass will wear away when pressed parallel to the file's teeth, forming an edge that resembles a sawtooth and has tips that reach down into the gullets. The most effective cleaning tool we have found is a piece of mild steel that has been heated and hammered thin and flat to remove really persistent debris. You can use a 1/4" steel rod, but a large ungalvanized nail would also function.

When it comes to sharpening metal cutting tool files, white vinegar is frequently advised as an acid. For use in the kitchen, 4-percent acetic acid is the kind you'll find. Among the household cleaning items in the store, there is also a 6-percent cleaner version. Etching a file takes a very long time, even with the stronger version. After three days, We saw that it had started to move forward a little. Sulfuric acid is a significantly more aggressive drain cleaner that can be used in approximately one hour.

Although it contains "metal inhibitors," it is evident that the acid still sharpens files despite their presence. The product needs to be handled carefully because of its high acid concentration, which may be quite hazardous if it gets on you or nearly anything else. Put on an apron, rubber gloves, glasses, and full face protection for lathe work.

NOTE: It is not advisable to use the acid undiluted; a solution of 10% acid to 90% water is sufficient. Never mix acid with water. Its fast exothermic reaction allows it to splash and produce a small vapor cloud. Sulfuric acid bottles feel hefty, as you will soon discover. Compared to water, it weighs nearly twice as much per unit of volume. The 10 percent solution will warm up substantially when poured into water, which is why we like to use glass containers over plastic ones. Use a respirator or work outside to avoid the vapor emanating from it.



After the file is etched, make a baking soda solution to counteract the acid. Stir the baking soda mixture until the water starts to dissolve and the soda starts to settle at the bottom.


Slide your fingertip towards the tang and press it on the teeth to see how sharp the file is before you submerge it. You will feel some resistance when using a dull file, but you won't feel the teeth grabbing the skin.


To remove any air bubbles, immerse the file in the acid solution and gently spin it. Extremely tiny hydrogen bubbles will be produced extremely quickly by the chemical reaction. It takes the acid around sixty minutes to complete its job. Take the file out of the acid and give it a quick wash to see how it's doing. We do the same fingertip test, and the sharpening is complete when we feel the teeth catch.


The acid in the file will be neutralized by dipping it in the baking soda solution. There will be a burst of carbon dioxide bubbles due to the remaining acid in the file. After giving the file a thorough rinse with clean water, dry it with a hair dryer, heat gun, or compressor blast.

To stop rust, some do-it-yourselfers spray WD-40 or another lubricant on the file. However, we think that gets messy and could cause the oil to slide across the work instead of cutting into it. Making sure the file is dry and not rusting by rubbing soapstone or, better yet, chalk over the teeth will also assist keep it from clogging while in use.

Think about grinding the teeth off one side while you're spending some time honing your files. Certain flat files have safe edges that are toothless to ensure that you are only working on one side of an angle.

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