The history of rasps is long and distingushed. Abrading instruments have been used for millennia. Archeologists have found rasps made out of bronze in Egypt, dating back to the Lisht Dynasty of 1200 - 1000 B.C., and iron rasps used by the ancient Assyrians in the 7th Century B.C. Rasps and files have a long and illustrious history in just about every area in the world.
Up until the 1850's, all rasps were hand-made. The process is theoretically very simple, but requires years of training to do well and consistently. Steel is forged and then ground to shape. Forging to shape is important because it gives a better structure to the steel. The grinding only serves to smooth the rasp blank perfectly so the teeth will be even. A punch is used to raise a tooth of metal on a piece of steel. Depending on how coarse or fine a rasp you want to make, the size of the punch and the weight of the hammer will vary. The entire surface of the rasp is covered in teeth. Stitching, as this process is called, is followed by straightening the rasp with wooden mallets. This is done very carefully so that the teeth are not damaged. The rasp is then hardened by a case hardening process that leaves the teeth very hard for years of work but only hardens the core of the rasp enough so that it won't bend in use. There are obviously more steps involved; these are the just high points. The key is that the teeth must be of a uniform size and spread out evenly over the rasp's surface so that the rasp cuts evenly.
While there were many early attempts to manufacture rasps using machines none were successful until the mid nineteenth century. Today all commercial rasps with the excpetion of Auriou and a half dozen other companies are made by machine. The manufacturing process is similar to the process described above, with the machine spacing the rasp's teeth. This can produce a good, but not great rasp, as there are several problems with this method. First, and more importantly, the machine's ability to space the teeth precisely results in a rasp that will cut roughly as each tooth follows in the path of its predecessor. Score marks in the wood will occur. Human workers, even trying their best to produce a absolutely regular rasp will end up with minor variations in the placement of the teeth. Consequently, each tooth will cut a slightly different path than the tooth before it, giving the rasp an overall much smoother cut.
The Nickolson #49 and #50 patternmaker's rasps are two exceptions to the machine-made rule. They are the last gasp of Nicholson's line of top-quality, random-cut rasps. They are machine-made, but the machine in question is a special gizmo that, using extensive skilled operator control, allows for minute adjustment in the position of the teeth so that the resulting spacing is slightly random, like a hand-cut rasp. These rasps cut very fast and very smoothly. They're more expensive than rasps that are totally machine made, but they work almost as well as much more expensive hand-made tools. The one hitch is that these two styles - the #49 and its finer cut cousin, the #50 - are the only two styles of Nickolson patternmaker's rasps currently being made. They're are great tools and we recommend them highly, but sometimes you need other shapes and these won't suffice.
This brings up the other advantage of hand made rasps: Hand cut means lots of selection. When everything is done by hand it is easy to make a huge range of different types of rasps in a low volume. This is very important now because up until recently, patternmakers were a big industrial user of rasp because of the need to precisely shape wooden patterns for casting. This trade is almost vanished, replaced by CAD and CNC equipment milling plastic and other more stable materials. Consequently most of the makers of rasps, and with the two exceptions noted above quality machine made rasps have vanished. There is not a huge demand for rasps and riffler rasps these days so volume is low and the only real variety of rasps and rifflers currently made are all hand made.
There are a few other makers of hand made riffler rasps in the world. However none of them are currently producing any tool anywhere near the quality of the Auriou rasps.
The tooth of a classically hand-made rasp is pointed and will cut cleanly. The teeth of a Nicholson #49 or #50 are similar but flatter on top. They also cut cleanly. On cheaper rasps and r?ffler rasps it is easy to see crushed teeth that were mishandled during the straightening process. Another problem with poorly made hand made rasps is that the teeth aren't even so you get scratches. The finess of cut is proportional to the size of the teeth. The speed of cut is mostly proportional to the density of teeth ion the rasp. Fine rasps should be covered in perfectly even smaller teeth. Coarse rasps should also be covered perfectly even larger teeth.
There have been no makers of hand-made rasps or riffler rasps in the United States for a long time. Nicholson has moved it's production out of the US and the quality of the 49 and 50 rasps has gone considerably down. Auriou rasps and rifflers, which we do stock are totally hand made by a factory started in 1856, currently with Michel Auriou at the helm. A huge range is available, even the coarse grades for stone-work cut very, very quickly and smoothly, but they are expensive. They are made in the classic French style, with all the rasps and rifflers coming to a point for maximum versatility and the teeth are densely space, pointed and not broken off. Fortunately they will last a long time and are well worth the investment in time saved while using them and the smoothness of cut will save a lot of finishing time. We also stock Gramercy Tools rasps which we designed and are made for us by a single maker in Pakistan, which has a long tradition of metalwork. We handle the rasps here.
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