File Cuts Explained: Bastard vs Second Cut for Metalwork
By Quality Industrial Abrasives and Tools | Benchmark Abrasives | Published: 2026-11-02
Category: How-to Guides
Bastard cut removes metal fast; second cut refines it. Learn which file to grab, how to match shape to the job, and a filing sequence that avoids common mistakes.
Quick answer
Start with a bastard cut file to move metal quickly, then switch to a second cut file for a smoother finish. Choose a mill file for flat edges and a round file for curved openings.
What the cut name actually changes
The cut name describes tooth spacing, not the file's shape. A bastard cut has coarser teeth that bite deeper and clear chips faster, so it removes more metal per stroke. A second cut has finer teeth that take shallower passes and leave a smoother surface. Neither cut is a finish grade on its own; the result depends on pressure, stroke length, and how often you clean the teeth.
Because coarser teeth cut deeper, they can also leave deeper scratches that take longer to file out. Finer teeth cut slower and clog sooner with soft metals. Match the cut to how much material you need to remove, not to how hard the metal feels.
Shape matters as much as cut
A mill file has a rectangular profile and a tapered point, which makes it the default for straight edges, slots, and draw filing. A round file has teeth all the way around and is designed for circular openings and concave surfaces. Using a flat file in a round hole or a round file on a flat edge wastes time and can distort the shape.
The farmer's own file is a two-sided flat file with a double-cut pattern on one side and a different pattern on the other, plus a large handle. That dual pattern lets one tool handle roughing and smoothing without switching files, but the flat profile still limits it to flat and slightly curved work.
When a second cut is the wrong first choice
If you start with a second cut on a rough edge, the fine teeth skate over the surface and clog before they remove enough metal. You spend more time cleaning the file than cutting. Reserve the second cut for after a bastard cut has brought the edge close to shape, or for light deburring where you do not want to change the geometry.
The exception is thin or delicate work where a coarse file can catch and bend the part. In that case, light pressure with a finer cut is safer than aggressive strokes with a bastard cut.
Step-by-step filing sequence
- Inspect and secure the workpiece: Clamp the part so the edge you are filing is at roughly waist height and cannot shift. Check for grit or burrs that could catch the file. A part that moves mid-stroke causes flat spots; test the clamp before the first stroke.
- Choose the cut for the amount to remove: Use a bastard cut when you need to remove visible material or reshape an edge. Switch to a second cut only when the edge is within a few strokes of final shape. If the file skates instead of biting, you started too fine for the stock you need to remove.
- Match the file shape to the surface: Use a mill file on flat edges and slots, and a round file on circular openings or concave curves. Keep the full face of the file in contact with the work. A round file used on a flat edge cuts only on a narrow line and wears unevenly.
- Set your stroke and pressure: Push the file forward on the cutting stroke with steady pressure, and lift it slightly on the return stroke. Use long strokes that use most of the file length. Dragging the file backward under pressure dulls teeth and clogs the cut.
- Clean the teeth before they load: Tap the file against the bench or use a file card when you feel the cut slowing or see chips packed between teeth. Clean before the teeth are fully clogged. A loaded file scratches rather than cuts; cleaning takes seconds and restores the cut.
- Refine with a second cut or the opposite face: After the bastard cut brings the edge close, switch to a second cut file or the finer side of a dual-pattern file. Use lighter pressure and shorter strokes. Stop before the edge is perfect; a few light passes remove the coarse scratches without overshooting the shape.
Files that match these cuts
- 6" Mill File (Bastard Cut): 6" Mill File (Bastard Cut) is a two-sided flat file with a single bastard cut pattern and a rectangular tapered point. The flat profile and tapered point make it a practical first file for straight edges and detail work before switching to a finer cut.
6" Mill File (Bastard Cut) - 8" Farmer's Own File (Second Cut): 8" Farmer's Own File (Second Cut) is a flat two-sided file with a double-cut pattern on one side and a different pattern on the other, plus a large handle. One tool covers roughing and smoothing on flat work, which suits a farmer's own file uses where you want fewer tool changes.
8" Farmer's Own File (Second Cut) - 10" Round File (Bastard Cut): 10" Round File (Bastard Cut) has teeth all the way around and a circular design for filing circular openings or concave surfaces. The round bastard cut removes material aggressively inside holes and curves where a flat file cannot reach evenly.
