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Sharpening Chisels & Plane Blades

Peter Young gives us some advice on sharpening chisels and plane blades.

If your chisel or plane blade is older and has had a lot of use, it may have some damage. The first thing you will need to do is remove any nicks from cutting edge – I think it is better to do this first up so that you don’t waste time on metal which may need to be removed.

The easiest method is to use a grinding wheel and hold the damaged edge more or less at a right angle to the wheel. For flat abrasives, hold the tool upright at a right angle to the cutting surface. This method will produce a square blunt end to the tool but we can easily bring that to a sharp edge at a later stage.

Flatten the back and polish - you only need to do this once for the lifetime of the tool but it is a really important step. You really only need to have a few millimetres at the cutting tip brought to a high polish, but in practice it usually means preparing 10mm or more.

For really damaged or rusty blades, I usually start with 80 grit paper on a granite block. This removes material quickly and lets me see how much work needs to be done. I then move through the grits (120, 240, 320, 400) still on granite. You don’t need to spend a lot of time on each grit, probably no more than about 20 – 30 strokes, but it is important not to miss steps and jump too quickly to a high grit.

The next step for me would be a diamond stone and this is where you would probably start if your blade is new. I then move on to waterstones (1000, 6000, 8000, 10000) to achieve a highly polished back. How far up the scale you take it is up to you and what you intend to do with the finished tool.

Now we can start working on the bevel. For a hollow grind you will need to set the tool rest of the grinding wheel to the required angle. There are a couple of different ways of doing this. For a new blade you can simply use the factory ground setting. Place the blade on the tool rest and turn the wheel by hand. Adjust the tool rest so that the grind mark is in the centre of the bevel. You can also make a guide by cutting various bevel angles on wood or MDF scrap.

When grinding plane blades it is important to keep the cutting edge square so check frequently. Some people use a marking pen to draw a square line across the blade as a guide. Keep checking the bevel to make sure you are grinding evenly and that the tool is not getting too hot.

You are finished grinding when a small bur appears right along the cutting edge.

Use an eye loupe or magnifying glass to help you inspect the cutting edge at this and later stages. Now that you have a hollow grind, you can continue sharpening using either a free-hand method or you can use a honing guide. For the free hand method you need to use your hands to keep the blade at a constant angle to the abrasive. The hollow grind has produced a heel and a toe on the cutting bevel with a hollow in between. If you keep the heel and the toe in constant contact with the abrasive you will maintain a constant angle.

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