A metal file is a hand tool used to remove small amounts of material from metal, plastic, or wood by scraping with many hardened teeth. It matters in workshops because it lets a worker shape, smooth, deburr, and fit parts with careful control. Unlike a power grinder, a file removes material slowly, which makes it useful for accurate finishing and small adjustments.
Understanding its parts and safe use helps produce cleaner work and prevents injuries.
Key Facts
- A file cuts mainly on the forward stroke when its teeth bite into the workpiece.
- Pressure = Force / Area, so higher hand force or smaller contact area increases cutting pressure.
- A coarse file removes material faster but leaves a rougher surface than a fine file.
- Single-cut files have one set of parallel teeth, while double-cut files have two crossing sets for faster removal.
- Work done on the file and metal is W = Fd, where F is applied force and d is stroke distance.
- A file should have a secure handle on the tang because an exposed tang can puncture the hand.
Vocabulary
- File teeth
- The raised cutting ridges on a file that scrape and remove material from the workpiece.
- Tang
- The narrow pointed end of a file that fits into a handle.
- Cut
- The pattern and spacing of teeth on a file, such as single-cut, double-cut, coarse, or fine.
- Deburring
- The process of removing sharp edges or small rough projections left after cutting, drilling, or machining.
- Draw filing
- A filing technique where the file is held sideways and pulled or pushed along the surface to produce a smoother finish.
Common Mistakes to Avoid
- Using a file without a handle is dangerous because the tang can slip into the palm and cause a puncture wound.
- Pressing hard on the return stroke is wrong because most files cut on the forward stroke and the return pressure can dull the teeth.
- Using a coarse file for final finishing is a mistake because it removes material quickly and leaves deep scratches.
- Filing without clamping the workpiece is unsafe because the part can move, chatter, or cause the file to slip.
Practice Questions
- 1 A student pushes a file with an average force of 35 N through a stroke distance of 0.25 m. How much work is done on one forward stroke?
- 2 A file makes 40 cutting strokes, and each stroke removes about 0.015 mm from a small edge. Estimate the total thickness removed.
- 3 A smooth final surface is needed after rough shaping a steel part. Explain why a worker should change from a coarse double-cut file to a fine single-cut file and reduce pressure.