How to Sharpen a Plane Iron

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One of the most familiar hand tools to most woodworkers is the plane. While there are several types of planes, all of them work on the same principle. The bottom of the plane is a flat surface with a slot in it. The plane iron or blade extends through this slot just enough to allow the plane to shave small amounts of wood from a plank as the plane is pushed over its surface.

To achieve the best results in my craft, I ensure that the plane iron is razor-sharp. Constructed of tempered steel, the blade is designed to maintain its sharp edge for a considerable time. However, even with such quality, after planing a few times, especially when working on seasoned hardwoods like oak, I find the need to sharpen it. Thankfully, once I detach the plane iron, honing it to perfection is a straightforward skill that I’ve mastered over the years.

The Sharpening Process

1. The end of the plane iron that is sharpened has a bevel

Most planes come out with the bevel already having been ground on the plane iron. If you would happen to need to create this bevel due to damage, the recommended angle is about twenty degrees for softwoods like pine and twenty-five to thirty degrees for hardwoods like maple or oak. 

The bevel can be ground on a bench grinder. It is possible to do this freehand, but if you have had an attachment for your grinder to hold the plane iron and set the angle, it is easier. Use a protractor to measure the angle for the correct pitch.

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2. When grinding the plane iron, the wheel should turn toward the blade with the bevel side up

It is a good idea to wear safety goggles when grinding any steel. By turning the plane iron so that the bevel side will be up, most of the debris from the grinder will be driven away from you and your eyes. The length of the bevel should be about 2 ½ times the thickness of the blade. Avoid applying too much pressure to keep from overheating the blade.

Plane Iron Sharpening

It is a good idea to dip the iron into water frequently to keep it from losing its temper. If you are grinding the plane iron freehand, move it back and forth slowly over the grinding wheel. A small burr may form, but this will be removed during the next sharpening step.

3. Use an oilstone for the final sharpening

The final sharpening can be done on any type of whetstone, but an oilstone is the easiest to use. The stone should be coated with an oil that is a mixture of one-half machine or shop oil and one-half kerosine. Usually, just a few drops along the surface of the stone is sufficient. When sharpening, I ensure the bevel of the plane iron contacts the oilstone at an angle between thirty to thirty-five degrees. Maintaining consistent and even pressure on the blade is crucial. I’ve discovered that the key to achieving the sharpest edge is to methodically push and pull the blade along the entire length of the oilstone.

(Know more about the bevel cut here!)

4. After several strokes, remove the burr on the opposite side of the plane iron

The sharpening should be complete after six to ten trips forward on the oilstone. Flip the blade over and hold it nearly level with the oilstone. Slide the blade back and forth without too much pressure with the burr against the oilstone. A couple of trips should be sufficient to remove the excess metal.

5. The plane iron needs to be tested for sharpness before putting back into the plane

There are easy ways to check if the plane iron is sharp. The first one is to hold the blade with the bevel facing up and gently glide it across your thumbnail. If it smoothly glides without catching, it’s not sharp enough. However, if you feel it bite your nail, it’s sharp and good to go. Another technique I often use is to dampen a small patch of hair on my arm or leg and glide the plane iron across as if it were a straight razor. A clean shave indicates it’s sharp and ready to go. Once I confirm its sharpness, I simply reattach the plane iron to the plane, and it’s time to get back to the woodwork!

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Robert Johnson is a passionate furniture maker & carpenter, sought after for his knowledge on the craft.
You’ve probably seen his down-to-earth wisdom in USA Today, Bobvila, Family Handyman, and The Spruce, where he has shared commentary and guidance on various woodworking topics.

Robert is the brain behind Sawinery, where he aims to share tips, tricks, and a passion for all things carpentry.

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