Every woodworker worth his sawdust is going to have a set of chisels of one sort or another and possibly one or two ordinary firmer or out-cannel gouges. Firmer gouges are a similar design to those used by woodcarvers to produce a shallow depression that might be found in a carved bowl. They’re often seen with a fingernail profile and with a little practice, aren’t too difficult to sharpen freehand on your favourite honing media.
I wonder though, how many woodworkers have a set of scribing or in-cannel gouges? In most respects, they look identical but differ in one significant way, namely that the bevel is on the inside of the blade, rather than the outside.
An in-cannel gouge is quite a specialist tool, but absolutely invaluable for precisely cutting an inside curve, as you’d find on the shoulder of a round component, for example, in the construction of a chair. I use them for all sorts of smaller stuff where I need to make a precise internal cut, such as tiny handles and, as such, there isn’t really any other tool that will do the job effectively.
The set shown in the pic weren’t bought specifically as in-cannel gouges, but were made from old firmer gouges obtained years ago from my local second hand tool shop. The outside bevel was removed by grinding very carefully (so as not to overheat the steel) which left the ends square and the blades somewhat shorter.
The big problem with in-cannel gouges is sharpening and honing the things. You’ll need to exercise the little grey cells to work out an effective way of producing that all important edge, whilst at the same time attempting to keep the end reasonably square; not an easy task by any stretch of the imagination.
When I first used these tools some years ago, I tried grinding the internal curve on the corner of a high speed dry grinder, which proved impossible. Then I realised that the only sensible way to do it was to hold the gouge on the bench (or vice) and use a small conical grinding wheel in a large power drill, but this proved too cumbersome. It wasn’t until I bought a Proxxon Mini Drill that I finally cracked it as it was now possible to grind the internal curve quite accurately.
Having ground the bevel, the next task was to produce the cutting edge.
An India slip stone or the small pink wheel is capable of producing the initial edge, which is workable, but nowhere near fine enough for detail work, so I then had the bright idea of making up some shaped mdf mandrels which could then be used in a pillar drill or later, an electric motor (with a chuck) mounted on the end of my lathe.
The mdf wheel was treated with a smear of Tormek PA-70 Honing Paste and Vaseline petroleum jelly to act as a lubricant, so that when this set-up is spun at high speed, a mirror shine and very sharp edge is soon produced on the internal surface. To finish the honing job and remove any residual burrs, the curved exterior is polished on the leather wheel of my Tormek T7.
Once I’d worked out a grinding and honing regime for these in-cannel gouges, they’ve proved to be invaluable for all sorts of tasks in the ‘shop where I need to cut an internal curve. If you’ve been very observant, you’ll also notice that my gouges have rather attractive London pattern, octagonal handles made of English walnut and this little turning exercise will very shortly be the subject of another forthcoming AxBlog.