NickWelford":7uffo35j said:
Since when do carvers have a bevel on the flat side?
Well … it's quite traditional to not have a flat side for a carving chisel. For a skew chisel, there is an obvious benefit in that there is no longer a 'right' or 'left' handed skew, instead you can just flip it over.
For the square edge chisel, it's a bit more subtle. The first thing to note is that there is not really any need for a 'flat' side to a chisel when carving. Flat planes (typically the 'ground', but also other surfaces inside the carving) are done with a wide and shallow gouge - see the 'Chris Pye' range from Ashley Iles for this idea taken to 11. Generally speaking, there's rarely a need for part of carving to be flat to within millimetres - and if there is, then it's for technical purposes (e.g. joining sections via mortise and tenon), and thus would be done with the tools for that (mortise chisel etc), rather than the carving chisels.
So, having obviated the need for a flat back, lets look at the advantages of the 'back bevel' - there must be some, else why have twice as many surfaces to sharpen each time!
The biggest difference from the typical bevel edge chisel is the sharpening angle. I generally aim for 10 -12 degrees each side, for a net 20 - 25 degrees cutting angle. This angle each side means that on a flat surface, when I hold the chisel by the blade in my off hand, it sits with the bevel pretty much parallel to the surface. This means that shifting the tip between cutting and not cutting is as fine a movement as a gentle twist - with the thumb and pinky finger both touching the surface in both positions. This hand position facilitates all types of cuts, from a two handed grip (primary hand on the wooden handle), for pushing, or slicing cuts, or a more active cut with one of the mallets.
At least for me, with the meagre experience I have, this hand positioning is the big advantage of the double bevel, as it facilitate very fine cuts. Sometimes, this leads to the back bevel being smaller (or larger) than the primary, depending on the size of ones hands and the length of the blade.
There are other ways of using a chisel, or course, where one's off hand is not resting on the surface of the work - but it is in this case that I see the major differences.
One other claimed advantage is that it puts the cutting edge in the middle of the steel, so that when one is taking large cuts with a heavy mallet, the cutting edge is less likely to roll, as it's supported on both sides. Separately, a single-beveled chisel can 'drift' a bit - which is often used to the advantage - but a back beveled chisel is claimed to be much less likely to drift. I say 'claimed' on both of those - they seem very sensible claims, but I've not done that much straight work (lettering is the classic use of it, I'm more into functional and sculptural forms) to be able to attest to it directly.
To not digress too far from the topic, these chisels do not strike me as the careful bevel selection of deliberate choice - I'd have no qualms at taking them to a grinder.
