Sharp knives are the foundation of smooth, accurate milling. Whether you're running stock through a benchtop planer or truing an edge on a jointer, dull knives telegraph into every board that follows — tearout, snipe, and burn marks are the most common symptoms. The good news: sharpening your own knives is an easy learnable skill that saves money and keeps you in control of your machine's performance.
Choosing your jig. The Deulen 12-inch Planer Knife Sharpener is designed for sharpening knives from 6”- 16”. Deulen 6-inch Jointer Knife Jig is designed to sharpen knives 4”- 8”.
No Set-Up needed!
Just make sure your knives are touching the bottom of the brass slots when tightening the SS set screws. The jig has been CNC machined to hold the knives perfectly straight. Home made jigs aren’t accurate enough. Dan has tried this and knows the importance of accurate machining. Dan hand-checks every jig on an inspection plate before packaging. Every jig is hand checked to be within 0.001” accuracy.
Packaging is another area of importance. Every jig comes in an airtight, waterproof clear hanging container to keep your tool safe. Dan even includes a foam pad in the bottom of the package in case it’s dropped
- Clean the knife. Wipe resin and pitch off both faces with mineral spirits before clamping.
- Place the knife in the Deulen jig. Lay the knife bevel-face down into the jig's clamping channel. The bevel face should be fully in contact with the sharpening surface. Tighten each end first then, tighten the rest of the screws. Tighten firm, not over-torqued.
Maintaining an Even Bevel
An uneven bevel is the most common sharpening mistake. It creates a curved cutting edge that produces inconsistent surface quality and wears unevenly. To maintain a flat, even bevel:
- Use a flat reference surface — a quality lapping plate or diamond plate rather than a soft Arkansas or oil stone, which can dish over time.
- Apply consistent, light downward pressure along the full length of the knife on each pass.
- Count strokes and match them on both sides of the bevel.
- Periodically check with a permanent marker: coat the bevel, make a few strokes, and inspect which areas the abrasive is reaching. Uncolored spots reveal low areas or angle inconsistencies.
The Deulen Lapping Plate provides a known-flat reference surface that stays true across sessions, which matters especially when you're sharpening multiple knives that all need to match.
Grit Progression
A sensible grit progression removes material efficiently while leaving a refined edge. The exact grits depend on the condition of the knife:
- 120–180 grit: Start here only if the edge has chips, nicks, or significant dullness. This removes metal quickly and establishes a new bevel.
- 240 Transition grit. Removes the deep scratches left by coarser abrasives and refines the bevel shape.
- 400–600 grit: The working-edge range for most routine maintenance.
Spend enough time on each grit to fully remove the scratch pattern from the previous grit before moving forward. Rushing the progression is the most common reason for an edge that looks sharp but isn’t.
A Repeatable Process Pays Off
The biggest advantage of sharpening your own planer and jointer knives is your machines feedback: It gets louder and harder to control the material as the knives dull. You develop a feel for how quickly your knives dull, what your machines perform like at peak sharpness, and when it's time to rotate to a fresh edge. A jig that holds repeatable geometry — like the Deulen 12-inch Planer Knife Sharpener or the Deulen 6-inch Jointer Knife Jig — makes that consistency achievable without years of freehand practice. Pair it with a flat reference surface and a sensible grit progression, and sharp knives become a routine part of your shop maintenance rather than an occasional project.