Monday, July 18, 2011

Sharpening unpleasant chisels

I have some Marples chisels I bought primarily for carpentry a couple years ago.  I always looked forward to tasks that called for them - creating mortises for hinges has been the most common but anytime I needed to do some "fine" work (by carpentry standards) I would grab them.  They do the work, with enough persuasion, but have never been sharp enough to be truly accurate or enjoyable.  Their metric dimensions (despite imperial labels) are also a con.  Some of the chisels in the set have never been used, so they will serve as a good example of how lame a tool can be right from the factory.

At any rate, I've decided to tune these up to the best of my abilities, partly to ensure I have good enough freehand honing technique before I move on to more expensive tools.

These are coated in a lacquer to protect them from rust.  This is a fine idea, except for the fact that the lacquer also interferes with sharpening, so it had to go.  I donned gloves and respirator and gingerly used some lacquer thinner which rapidly did its dirty work.

Here is a chisel back, ready to be polished.  You can easily see the factory tool marks and the overall hazy finish:

This is a shot of the front:

Since they are new, I did not need to grind and skipped the 220 grit wetstone.  A good while was spent on the 1000 grit, a little bit on the 4000, and the 8000 brought about a mirror finish rapidly.  It is very difficult to photograph, but the flattened and polished section of the back truly is mirror-like now:

After bringing a tiny section of the top to a similar mirror polish, a slight 2ndary microbevel was added, just barely visible here as an extra glint of light on the edge.  The idea is that the microbevel will dull quickly but only take a few strokes to resharpen (rather than the whole cutting edge).

This last photo just shows an unpolished chisel on the left, and one which I worked on the right.  They now cut pretty well, and might even be serviceable for fine woodworking except for the unpleasant (poorly balanced and topheavy) handles and the fact that they are metric despite being labelled in inches.  Chisels can and should be used as measuring devices - making a dado or groove the width of a 1/2" chisel, for example, instead of measuring, marking, and then cutting.  However, this set is metric and uses "close enough" imperial labels, which are not "close enough".

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