Reply To: Mallets and Chisels
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Having chisels of various brands, and after close to two hours to get a 2” Robert Sorby Standard chisel flat, I carried out a small investigation on any correlation between price relative time to flatten and deviation from nominal width.
I included 6 chisels of various widths (please see attached photo). For all except the 1st (leftmost one) flatness was first checked on an 8 000 grit diamond stone, just in case any of the chisels would be flat from start. Flattening was then carried out on 600 and 1 200 diamond stones, A little was also done with the 8 000 one.
The idea was to have number one as reference, but it turned out to be an utter outlier, so the 2nd from left had to substitute. It took 15 minutes to get its 40 mm (1 9/16”) blade flat.
To adjust for differences in widths the remaining chisels were at most flattened to their widths / 40 mm * 15 minutes, The sizes of the chisels were measured with a calliper, and deviations of less than 0.1 mm (1/256”) were accepted as the chisel having nominal size. Compensation for variation in hardness in steel was for the simple reason that I don’t know how not done.
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1) Robert Sorby Standard chisel 1½” inch (£50): 50 minutes after having resorted all the way to a 220 grit stone, and still there is a dent just above the edge. It was off by 3/128” (0.6mm)
2) Hultafors All Metal 40 mm (1 9/16”) (£18): 15 minutes and to dimension. This is a tool that largely is in pursuit of a purpose. Being one piece of a steel going all the way to the top, the impact of a mallet blow is transferred directly to the edge, which – at the 25 degree bevel – immediately breaks on anything but soft construction spruce. However, its shape makes it good for pairing away glue. It’s also good for making knife walls.
3) C.I. Fall 14mm (35/64”) (£7): This chisel was given 5 minutes which is a little more than what it should have been allotted. A minute or two more would have flattened the last remnant above the edge. It’s size was what it said. It’s a very nice chisel, quick to take a very sharp edge that does not last very long.
4) Bahco 424: 18 mm (also stamped as ¾”) (£15): After 7 minutes this chisel was very close to flat. There is just a small imperfection proximal to the edge. It was dead 18 mm wide, which actually is a bit from ¾”. The bevel of this chisel is quite undecided. The proximal part is at 25 degrees, but then the terminal 2 – 3 mm are at 30 degrees. While not the most comfortable one, it is still a chisel. More narrow ones have been good enough for mortising not that small amount of red oak.
5) Robert Sorby Gilt Edge, Rosewood 1” (£40): The allowed 9 minutes rendered this one very close to flat. It is 1/100” below its stated width, but I asked the company to find me one that was as close to 25 mm as possible. A delight too look at, hold in one’s hand, and despite being quite thin it sustains the mallet well (The coffee table project establishes that, I think).
6) Lie-Nielsen 5/16” (7.93 mm) bevel edge chisel (£55): Flat from the start, to dimension, and superb to work with.
That these chisels came out short just proximal to the edge can of course be due to me certainly not being the most skilled one, but I would like think it is how the chisels were flattened during manufacturing. Except for the Lie-Nielsen, they all showed grind marks as if flattening was done by pressing them to the flat surface of a grinder; and that is exactly what I believe takes place. The worker puts the chisel to grinder and, perhaps, uses his/her fingers to press down. On a dry grinder, that will result in the centre of the edge being most exposed to pressure and heat.
The somewhat less than favourable results by what possibly should be Sheffield’s top of the line, is a bit depressing for someone who believes in buying “made in GB”; but a pair of duplicate (by mistake) 5/16” Robert Sorby Sash Mortice Chisels which deviated by 0.3 mm from each other, do seem to support the notion by Mr. P. Sellers in a blog item from 2014, that there is room for improvement on precision.
/soj