Reply To: Quality ferrules and hoops and the English registered firmer chisel
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Chisels come as flat as the need to be, after all they are not planes and modern chisels are ground from a billet of steel.
In reality, if you are only using the chisel for chopping mortises and slicing, then you only need to have the last 1/8 to 1/4 inch flat and polished because it is one side of your cutting edge. The rest of it plays a supporting role, so to speak.
For chisels that are used for paring, then again, providing that the edge and a few registered points along the backs are mainly flat, then that’s good enough. When all is said and done, we don’t need engineering tolerances in wood. The blade will flex in use and render close tolerances useless.
Paradoxically, Japanese chisels and plane blades intentionally have a hollow section along the centre of the back; only the back 1/4 inch or so of the bevel and a section up each side is flattened. Their reasoning is that it is less effort to maintain a small amount of flat metal at the important points of contact than the whole surface.
A little bit of work on polishing the backs progressing down the grits each time you sharpen will, in time, give you a true, flat back, if that’s what you wish.
In the most recent videos, Paul Sellers is intentionally using inexpensive chisels bought from a supermarket – new, grind marks and all to begin with. He’s been using them for a couple of years or so and if you stop the vid and look carefully you’ll see that he’s polished the business end, but further back the grind marks are visible although beginning to fade away. Come back in a couple of years and they’ll have mostly disappeared.
Good luck.