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Tuesday, 30 March 2010

More Haste – Less Speed

Clifton planing ebony walnut and oak

When you first start working with handplanes it is inevitable that sooner or later you will come across the problem of tearout. It is a common problem and every time you think you’ve cracked it another tricky piece of timber comes along that doesn’t want to play nicely. It usually happens because the grain of the timber is not all flowing in the same direction so the cutting edge of the plane iron is no longer cutting the fibres but instead is splitting them away from the surrounding material.

There are a broad range of weapons in the cabinetmakers arsenal to tackle this issue but it’s all too easy for experienced makers to omit the first and easiest way when they are advising others on how to tackle it, probably because they do it habitually and without thinking.

Clifton vs. Oak burr

Assuming your plane iron is sharp, the first port of call when you experience tearout is to slow down – right down. Nothing else changes, your stance, distribution of pressure on the plane, angle of the plane to the work, all remain exactly the same, you just take your good old time - perhaps ten seconds or so per foot of timber planed.

Observe the shaving as it emerges from the mouth, the shaving contains a wealth of information about what just happened at the cutting edge. Holes with flowing shapes and very thin frail edges indicate low spots, changes in the texture of the shaving indicate patches of reversing grain that the plane is coping with already and jagged holes with thick edges indicate areas that it is not coping with.

Quite often the simple act of slowing down is enough to either make the problem disappear completely or reduce it to a couple of thumbprint sized patches that can be cleaned up afterwards with a thin cabinet scraper.

The next simple step is closing up the mouth to a slit and backing off the depth of cut so that the plane is only just cutting, a really light wispy shaving invariably produces a finer surface finish than a thicker one.

Honing your cutting iron is the next step, as the first few passes with a freshly honed iron are much less prone to tearout. The final finishing passes on a piece of timber should always be taken with a freshly honed cutting iron, regardless of whether you only honed it five minutes ago or not.

Only when you have worked your way through the 'low hanging fruit' that requires no additional kit and the bare minimum of extra time should you start thinking about steeper pitches or scraping.