How to Lap Chisels

Lapping a chisel simply means to flatten the back, or face, of the chisel; it is the first part of the sharpening process. Lapping a chisel is actually a two-step process (the first step is to lap the sharpening stone itself). A stone that is not flat cannot produce a properly lapped chisel. Ideally, you will start with a coarse grit stone and progress through a series of medium and fine grit stones to polish the chisel blade. Each finer stone will remove any marks made by the previous stone.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• Sharpening stones
• Bucket of water
• Spray adhesive
• Granite surface plate or 12-inch x 12-inch scrap of granite
• 220-grit sandpaper
• Pencil
• Honing oil
• Chisel

1. Place the sharpening stones in a bucket of water, if they are water stones. For oil stones, skip this step.

2. Spray adhesive on the granite surface plate or scrap of granite and adhere the sandpaper to the granite with the grit facing up.

3. Remove the stones from the water and make several pencil marks across the face of the stones. Apply honing oil to the sandpaper if using oil stones.

4. Rub the stone on the sandpaper in a figure eight motion to flatten the face of the stone. For water stones, occasionally wash the slurry created by the flatten from the sandpaper using water. For oil stones, wipe the slurry away with a cloth. Check the surface of the stones periodically to see if the pencil lines are gone. Once the lines are completely erased, the face of the stone should be flat.

5. Lap the chisel by rubbing the back of the chisel on the sharpening stone using a back and forth motion. Alternate the motion as you progress through grits by holding the chisel blade on a diagonal and moving it side to side. When you finish with the finest grit stone, the back of the blade should resemble a shiny mirror.

Tips & Warnings

• Most new chisels will need to have their factory coating removed by wiping them down with lacquer thinner before lapping.
• It is not necessary to flatten the entire back of the chisel. Only the last 1/2 inch or so needs to be flattened to properly sharpen the blade.

References

• "Complete Guide to Sharpening"; Leonard Lee; 1995