How to Sharpen a Knife With a Diamond File (Field Guide for Beginners)
- Micah Gillette
- 6 hours ago
- 5 min read
Sharpening your survival knife is a very simple task and one that will pay dividends. A sharp knife makes every outdoor task easier (at least the ones you need a knife for. A diamond file gives you a simple, reliable way to sharpen your knife anywhere, even with zero prior experience. If you can hold a steady angle, you can sharpen your blade. This guide walks you through the exact process we teach in our classes and in the video below.
Jump Ahead
Introduction
If you want to keep your gear working for you, this method is perfect for any skill level and will keep your blades sharp. It works whether you are at home or out in the field and need a quick touch-up. The diamond file does most of the work, so there is no need to muscle anything. Your only job is to keep a steady angle and follow each step. Pro tip: A quick tune-up after each use saves time at the end of a trip and keeps your blade in top shape. Happy sharpening.
Watch the Full Tutorial
Gear You Need
This is a gear-based tutorial, so here is everything you need up front.
Quick Note: Our gear links are Amazon affiliate links. If you pick up a tool through one of them, it helps support our knife-sharpening habit at no extra cost to you. Thanks for keeping the adventure going.
Why a Diamond File Works Well
So why use a diamond file? They have a few advantages and help you avoid a few common pitfalls compared to other sharpening tools. Diamond files work on almost every blade or tool you will come across. They wear evenly, unless they are used incorrectly, and they do not require water or oil. They stay flat, which makes it much easier to match your angle. They also work in wet, cold, humid, or hot environments. All of this makes a diamond file one of the most dependable sharpening tools you can carry in the field.
Understanding the Bevel
The bevel is the flat angled surface at the edge of your blade. This is the only part you are actually sharpening.
Different tools use different bevel angles:
Small carving tools use steeper angles.
Most survival knives use a medium angle.
Axes and choppers use shallower angles.
Your goal is not precision to the degree. It is consistency. Matching the angle each stroke is what creates a sharp edge.
How to Sharpen a Knife: Step-by-step
These steps follow the same order as the video to keep everything consistent.
Step 1. Stabilize the Knife
Brace the knife against a table edge or clamp it lightly. Keep your guiding hand behind the edge for safety.
Step 2. Color the Bevel (Optional) Use a marker to fully color the bevel on both sides of the blade. When you start sharpening, this gives you instant and easy-to-see visual feedback. It is not required, but it helps a ton, especially when you are just getting started.
Step 3. Match the Factory Angle
Start with the 400-grit side of the file.
Place the file on the bevel and tilt until it sits flush on the colored area.
The marker tells you what is happening:
If color rubs off evenly, your angle is correct.
If color stays on the top side, you are too steep.
If color stays near the cutting edge, you are too shallow.
Step 4. Push the File Into the Edge
Push the file toward the cutting edge instead of dragging away from it.
Dragging away builds a burr that just flips back and forth and dulls quickly.
Use smooth, controlled strokes with light to moderate pressure.
Step 5. Keep the File Perpendicular to the Edge
As the blade curves near the tip, rotate the file so it stays perpendicular to that curve. If you keep the file straight while the blade curves, the tip will never sharpen properly.
Step 6. Work in Three Zones
Mentally divide the blade into three zones.
Tip
Middle
Heel
Work each zone with the same angle and steady movement. This breaks the process into manageable parts and avoids uneven sharpening.
Step 7. Make Three Passes Per Side
Sharpen the entire first side of the blade with three full passes.
Flip the blade and make three matching passes on the second side.
Step 8. Check the Marker
If the bevel is clean and free of color, your angle is correct.
If not, adjust your angle and try again.
Step 9. Switch to 600 Grit for Finishing
Make a few gentle strokes on each side using the fine grit.
You are not shaping the bevel here. You are polishing it and removing any micro burrs.
Step 10. Clean and Oil the Blade
Use rubbing alcohol to remove any remaining marker.
Add a thin coat of oil to protect the steel from moisture.
How to Test Sharpness
Paper test:
If the blade slices cleanly, it is sharp.
If it snags, correct that zone.
Cordage test:
If the blade slides instead of biting, sharpen more.
Light reflection:
A sharp edge will not reflect light.
Shiny spots show where the edge is still dull.
Common Mistakes
Changing your angle while you sharpen
Pulling the file away from the blade
Using too much/not enough pressure
Forgetting to rotate at the curve
Over-sharpening one side and ignoring the other
Consistency prevents almost all sharpening issues.
Field Sharpening vs At-Home Sharpening
You should get your blades into top condition while you are at home. Take the time to set a solid angle and make them razor sharp. That way, when you are in the field, you only need a few quick touch-ups to keep everything performing
Maintenance Tips
Wipe the blade after use.
Dry it before sheathing.
Oil lightly to prevent rust, especially in humid environments.
Touch up regularly rather than waiting until the blade becomes noticeably dull.
Make this a habit not a chore and your blades will always preform.
Want More?
If you found this guide helpful, there’s plenty more to learn. Subscribe to our Six Point Survival Newsletter for monthly tips and field-tested gear advice, and check out our YouTube channel for real-world demos and survival lessons.
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~ Micah Gillette
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TLDR
Color the bevel.
Match the factory angle.
Push the file into the edge.
Rotate the file as the blade curves.
Three passes per side on 400.
Light cleanup passes on 600.
Wipe, oil, and you are done.