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How to sharpen an auger bit?

How to sharpen an auger bit

Shop for Auger Bits
An auger bit file alongside an auger bit For this task, you will need an auger bit file at the ready! This is a type of file that has been specially designed to reach in to sharpen the cutting edges of an auger bit without causing damage to the flighting or guide screw. They are sold individually, and in one size only,For more information on these tools, see: Files
Diagram illustrating the parts of an auger bit including the spurs and cutting edges The areas that you are looking to sharpen are the two spurs and the lips. (There may be two of these, or just one.)

Sharpening lips and spurs

Image of a DIYer sharpening the cutting edge of an auger bit with a file

Step 1 – Sharpen lips

Sharpen the lips on your tool by giving them several strokes with your auger bit file. The lips are located near to the guide screw, at the bottom of each of the spiral flightings (there may only be one if you have a single-twist auger). To make sure you are following the right cutting angle, line your auger bit file up with the slope of the blade. It’s important that you don’t change it!

A DIYer sharpening the spurs on their auger bit for ease of cutting

Step 2 – Sharpen insides of spurs

Using the same technique, file inside the spurs, matching the angle of the file to the inside surface of the spurs so as not to change the geometry of the tool.

Image showing a DIYer sharpening the wrong part of an auger bit It’s important that you don’t file outside the spurs, as doing so will wear away material on the edge of the bit and reduce the size of hole that it will drill.
Image of a hole drilled by a recently sharpened auger bit

Step 3 – Test it out

Your auger bit should now be sharp. You can test it if it is by drilling a hole in some scrap wood. If it’s still struggling to bore a hole, repeat this process from step one.

Sharpening the guide screw

A tub of valve grinding paste which is used to sharpen the thread of the guide screw on an expansive bit When sharpening a guide screw, the best results can be achieved using grinding paste, a compound containing abrasive particles that are designed to wear down imperfections in metal surfaces that are difficult to reach.
DIYer making a hole in a piece of wood with the guide screw of the expansive bit

Step 1 – Create reservoir

Using the screw of the bit you would like to sharpen, bore just far enough into a piece of softwood for the guide screw to fully enter the wood, then remove the bit.

DIYer collecting grinding paste on a toothbrush so that it can be dabbed into the hole that was made with the guide screw

Step 2 – Apply grinding paste

Apply some fine grain grinding paste into the screw hole with the implement of your choice (you might use a toothbrush, a scoop or even a lollipop stick).

Turning a guide screw in a hole containing grinding paste to sharpen the thread

Step 3 – Grind screw sharp

Reinsert the guide screw into the bore hole and twist it backwards and forwards. This will cause the abrasive particles in the grinding paste to remove any dirt and sharpen the edges of the thread.

Rinse off the grinding paste using water if the packaging says it is water soluble

Step 4 – Clean off excess paste

Remove the bit from the bore hole and clean off any paste left on the screw. Check the packaging for the grinding compound to see if it’s water soluble. If it is, you can rinse it with water.

A can of water displacing oil that can be used to clean non-water soluble grinding paste off an expansive bit If not, you will need to spray water displacing oil onto the guide screw before wiping it with a cloth.

Wonkee Donkee Tools