When you need to apply more pressure to a marking knife to cut and it becomes harder to run along a surface, you know it has become dull and needs sharpening. When this happens, you need to sharpen the blade.
The blades of marking knives are produced from very strong materials. However, they are designed so that they can be sharpened, no matter what material they are produced from.
A water stone is the perfect sharpening tool for a marking knife. Water stones are categorised by grit fineness. A 4000 grit water stone is the perfect choice when sharpening exceptionally hard steels.
This is a step-by-step guide for sharpening a double-bevel marking knife. You will need to perform each step for both bevels. For a single-bevel marking knife you will only need to sharpen the one bevel.
Step 1 – Wet grit stone
Soak the water stone in some water, ensuring it is fully submerged for ten to fifteen minutes.
Step 2 – Flatten back
Place the flat back of the blade against the grit stone so that it rests entirely on the flat stone. Hold one finger on top of the blade with the rest of your hand holding the handle. Rub the back of the blade in a circular motion, applying even pressure.
Step 3 – Sharpen bevels
Turn the marking knife over so the flattened edge is facing you. Very gently, rest your hands on the stone, angle one of the bevels of the knife until it is flat on the stone and pull it towards you a few times. Change over to the other bevel and repeat the action.
Step 4 – Round tip of blade (optional)
If you want a slightly more rounded tip to your blade, draw the knife back, rotating as you go, just a couple of times, to get a good round point.
A rounded, sharp tip on your marking knife can improve the way it cuts along the grain. When scribing along the grain a straight sharp tip can follow the grain, causing the guideline to go off course.
Step 5 – Check blade
An edge is obtained when there is a mirror shine. Check the blade to see if there is a mirror shine on each of the bevels. This is a good indicator that you have sharpened the blade well.
Step 6 – Test blade
Use an old piece of wood and test the cutting edge of the marking knife. If it is still difficult and you need to apply quite a bit of pressure to scribe a line then continue to sharpen the blade. If the blade is cutting into the wood with hardly any pressure, the blade is sharp enough.