Thursday 17 September 2009

What Tools Do I Need? part 5 Sharpening

The last Item on our list a sharpening system, should perhaps feature right at the top, as this is arguably the most important part of your tool kit. It ensures all your edge tools are in working condition, no matter what quality. Unfortunately most people setting out in the field of woodworking give it scant attention in their eagerness to get started. This is unfortunate, as it generally results in frustration. Throwing the tool down in disgust, they blame either the quality of the wood, the tool or their own lack of skill; in truth it is just a lack of understanding two things. Firstly the right understanding of sharpness and secondly how one may achieve it. A perfect cutting edge, is the meeting point of two converging angles prepared in such a way that all imperfections are removed; a mirror surface. This is achieved by grinding and honing with progressively finer sharpening stones.

Regrettably this rarely happens on the novice’s bench, many are content to use some old misshapen piece of rock from granddads shed or the ubiquitous oilstones of indeterminable grade; at best there may be fine or course marked on them. Stones that are deformed or even slightly hollowed are useless for our purposes and will quickly ruin any tool by rounding the back of it. For a chisel this is the part of the tool that bears on the timber as a guide, this helps control the cut, so needs to be perfectly flat; On a plane blade, this is the area that determines the angle of cut and very importantly mates with the chip-breaker. Even the slightest gap here will result in shavings being trapped; this will entirely choke the plane even after one or two passes. For these and a host of finer points blades need to be perfectly flat; flattening the blade of an edge tool is actually the first job you will need to do after you take it out of the box. Because even the best quality tools will need a little tuning before use, no matter what it says on the wrapper.

They may feel sharp and may even give you a nasty nick, but they will not be the surgical sharpness we are looking for; an edge that will leave the cut wood polished and ready to take a finish. If you were to place a new blade, or one that had been sharpened on a carborundum stone, under a magnifying glass, you would see thousands of small scratches. Then if you further magnified the edge you would then see that these scratches now looked like a ploughed field and created deep furrows at the tip of the blade. Try pushing a saw sideways over a piece of wood, not only does this require considerable effort, but the result is hideous. Now, this is exactly what happens, only in smaller scale, when using a badly sharpened blade.

I could list all the pro’s and con’s of the different stones available, but this is adequately done elsewhere and is here I believe redundant. Because you are only looking for information that applies to your situation and helps you get started quickly and easily; you do not need stones that constantly need flattening or dressing. Diamond or ceramic stones are without doubt the best choice and I shall be looking at different types in my next post.

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