Argus":25xqwzfl said:
I used to live in Cotham forty odd years ago - not sure if B D were there then.... I think that they might have been.
I seem to recall that some of their chisels were made in Germany by an outfit called Schwarchter (or some thing similar), though they were stamped 'Bristol Design' and I bought a few back in the 80s.
Not quite correct - they sourced the steel from Germany (nearest they could find to straight unalloyed carbon steel), but the forging and grinding were done in France. I can't confirm this, but I suspect the forge was the Forge de Saint Jeury, of Auriou rasp fame. The first trade name they chose was 'Scharwaechter', but they quite soon dropped this. I have one chisel so stamped, but the other five are stamped 'Bristol Design', or in the case of one tiny chisel, just 'Bristol'. The Scharwaechter came with an unfinished boxwood London pattern handle, the others had lacquered boxwood London pattern, and I think boxwood carver's pattern or unhandled were available as options.
I suspect that the reason for their reputation for out-of-flatness may be the steel choice. One of the downsides of straight carbon steel of about 1% carbon content is that it only really responds to a very fast quench - water or brine. It doesn't harden to a very great depth, either. The result is a thinnish piece of hard steel with a lot of quenching stresses locked into it, which, when you start grinding it, release unevenly to some extent, causing slight distortions. The effect is minimised on even cross-sections such as the traditional 19th century firmer chisel, but become more pronounced in sections such as a bevelled-edged chisel, and it would be even more pronounced on a long piece such as a paring chisel, though less a problem with shaped tools like carving gouges. The stresses can't be relieved, because to do so effectively would require heat treatment well above the acceptable tempering temperature for a wood chisel.
This problem (and that of slight dimensional changes on hardening) caused 19th century toolmakers, especially those engaged in making engineering gauges, much angst. Consequently, when metallurgical experiments in the late 19th century developed a low-alloy high-carbon steel that responded to slower oil quenching, thus causing much less internal stress in workpieces, it was siezed upon with some enthusiasm. The new steel didn't change dimension on hardening either, and hardened to greater depths. It was therefore much easier (though not totally infallible) to grind to shape without distortions happening. That new steel (with minor improvements) is what we now call O1.
The one advantage of straight carbon steel over O1 is that it is capable of developing a slightly sharper edge. The edge-taking of O1 satisfies most people most of the time, but I can see why Bristol Design tried the straight carbon steel, to get as close to the edges 19th century Cast Steel chisels will take. Had they replicated 19th century chisel shapes, they may have had fewer distortion problems - but that's a 'what if', not what we actually have.
I still think BD were brave and forward thinking to invest so much in their chisel line. If nothing else, it generated a huge amount of interest, and helped to encourage others to make and sell fine quality tools by demonstrating that there is a market for them. We owe Charles Stirling a generous vote of thanks for that.
(Edits for spelling corrections, and to add 'by demonstrating......market for them' to second last line.)
