Honing Chisels and Plane Blades
Squeeze a thousand woodworkers in a large workshop, give them the brief ‘’honing chisels or planing blades,’’ light the blue touchpaper, lock the door and retire. If you were to come back in a couple of hours and make an attempt at collating the results, the chances are you’d end up with a thousand answers.
The Ultimate Edge
Everyone has their own way of achieving ‘the ultimate edge’.
Sharpening and honing is absolutely central to all woodwork activities that involve cutting and shaping timber.
Given it’s a precarious and contentious area to discuss, the basics are remarkably simple. It’s their variations that make the whole issue complicated. A honed edge is nothing more than the intersection of two flat steel surfaces that meet at an acute angle. At its most basic, for any given angle, the finer and more polished the intersection, the sharper the edge. The reverse is also true; an intersection that’s crude and jagged or even slightly rounded will be less sharp or even blunt.
The cutting edge (or honed bevel) is usually a thin strip of polished steel at around 30°. It’s this small area which is the focus of attention. The steel behind the edge is usually ground away at 25° and serves only to support and reinforce the honed bevel.
There are several excellent systems to produce the 25° ground bevel. And the Tormek system is pre-eminent and probably one of the best available.
Although there are dozens of methods of honing to achieve an edge, the one essential item is a sharpening medium. I’ve tried oilstones, waterstones, diamond stones and ceramic stones. All of these media have their advantages and disadvantages. But nowadays my preferred method is the so called ‘Scary Sharp’ system, which has become quite popular over the last few years.
In this system, films of fine abrasive are stuck to a dead flat surface, such as a block of thick float glass. The abrasive is used to hone the edge so that once it’s torn, or ceases to cut effectively, it’s simply removed from the glass plate and a new one stuck in its place.
Freehand or Honing Guide?
The other area which is liable to raise hackles, is the issue of freehand sharpening versus a honing guide. Both have their proponents. The main advantage of freehand is it’s much quicker, but less accurate. Although it’s slower to use a honing guide, the angle required (usually 30°) can be found with absolute precision.
I can sharpen blades freehand, but I now prefer to use a honing guide. I’ve tried different types of sharpening media over the years, the same can be said for honing guides. Each has its merits and disadvantages. The one I now use is the quite excellent and extremely versatile Veritas MkII together with the Narrow Blade Clamp Head attachment for chisels.
The ‘Ruler Trick’
Honing the 30° bevel will produce a minute burr on the reverse (or back) of the blade. This needs to be removed and the surface left with a polish. One way is to use a very thin, sprung steel rule which is positioned at one edge of the sharpening media. The back of the blade is placed on the rule and the burr honed off on the other edge of the stone, producing a very small ‘back bevel’. Using a long forgotten trigonometry formula, the back bevel is about 0.6° when using 50mm wide stone and an angle that small has no practical effect on a plane blade.
The burr on a chisel blade should always be removed by placing the blade flat onto the sharpening media. The ‘ruler trick’ should not be used in this instance.
To Strop Or Not To Strop?
Another area that’s liable to cause fisticuffs among woodworkers is stropping. For centuries, traditional barbers offering a wet shave use a leather strop to produce a super-fine edge on a cut-throat razor. And this technique can be used to good effect on plane and chisel blades. The leather is dressed with a lubricant (machine oil, petroleum jelly or similar) and then a very fine abrasive paste is rubbed into the surface.
When the blade is pulled over the strop several times, the effect is to refine an already lethal edge. On both plane and chisel blades, it’s only the bevel that should be stropped. Some ‘rounding over’ may occur if the back is finished by stropping.
Having examined honing, the next post will look in more detail at the Veritas MKII Honing Guide. And how to get the best out of it using the ‘Scary Sharp’ system. In the meantime, if you have any sharpening tips or tricks, join in the conversation by leaving a comment below.