Files, rasps and rifflers

Words and photos: Richard Vaughan

Files and rasps are sadly underappreciated by most woodworkers. They tend to be dismissed as only for rough work whereas these excellent tools are an essential part of any woodworker’s selection. And I am referring to fine woodwork.

There certainly are rasps rough enough to really rip a surface, but the patternmakers style of rasp is a very fine tool indeed for rapidly shaping wood and leaving a formed rather than tormented surface. There are also other variations worth knowing about.

Files come into use when you need to smooth a tear on a drill bit shaft for example, or sharpen a screwdriver or scraper, or when tuning a plane. They also come into service for modifying hardware such as hinges, screws and handles. And they do shape wood as well as metal, often more conveniently and efficiently than sandpaper.

The intention of this article is to give a better understanding of them. There are good reasons why they have been in use for probably 5,000 years on stone, steel, lead, bread, horse hooves, wood and just about any other material put into service by humanity. The range available at the start of the 20th century was vast, and although demand has diminished with the waning of trades such as patternmaking, watchmaking and locksmithing, there is still an impressive array of many hundreds available.

Files and rasps

1. Detail of single cut file showing negative rake of teeth. The file cuts towards the right here.

First we need to distinguish between files and rasps. Files have rows of parallel sharp ridges and can be single or double cut. On single cut files the teeth are at 65–85° to the centre line (photo 1).

2. 10" double cut files showing the difference between second cut and bastard.

On double cut files the first row, known as the overcut teeth, are at 40–45° to the centre line. The second row or upcut teeth are at 70–80° to the centre line (photo 2).

The teeth are angled in order to give a slicing cut, and the angle is set according to the hardness of the metal the particular file is intended for. Double cut files are more aggressive but give a rougher finish than single cut files. A general rule is ‘the harder the metal the finer the teeth’.

File teeth are made with a negative rake (photo 1). This means that the angle on the face of the tooth slopes back rather than forward, as it does on most saw teeth for example. This has the benefit of being less likely to jam metal filings into the gullet. It also makes the tooth stronger. A positive rake would undercut the tooth and leave less metal to support the cutting edge.

In use this negative rake means that if you push the file too quickly it will have a tendency to bounce over the surface rather that cut it. Using the file with deliberate strokes is much more effective. It’s yet another instance of the ‘less haste more speed’ principle which guides good work.

3. Detail of teeth on the convex back of an Auriou 10", 5 grain rasp.

Rasps on the other hand have individual teeth, each formed by driving a punch into the surface of the annealed (heat softened) steel. The resulting raised flap becomes the tooth. The tool is then case hardened (photo 3).

Up until the mid-19th century all files and rasps were hand made—though we ought to acknowledge that the phenomenal Leonardo da Vinci did design a machine for cutting them. It took several years of training before a file maker was judged to have the consistency in his hammering of chisel or punch essential for accurate files and rasps.

Identifying the comparative coarseness of cut for both files and rasps is done by three grades for the American pattern tools. Years ago there were seven grades but nowadays the coarsest is the bastard, then there’s second cut and finally smooth cut.

4. From the top, 10", 8" and 4" bastard files

But beware. For some arcane reason the grades of coarseness are only comparable in files or rasps of the same length. A long rasp or file is actually a coarser cut than a short rasp or file of the same grade (photo 4). When asking for a file or rasp you should ask for it by length, name and grade. For example, for the finest American pattern file you would ask for a 4" mill smooth. A 12" flat bastard would really do some shape changing.

5. Left to right: four needle files, rat tail file, rat tail rasp, four riffler rasps, riffler file

Swiss pattern tools have seven grades ranging from #00 to #6, which is the finest. Swiss files are finer than the American pattern and suitable for more precise work, such as in jewellery. Swiss pattern files are shown at left in photo 5 and are most likely sourced from a jeweller’s supply outlet.

6. From top: Auriou grains 9, 15, 5

The French have a different system again. Theirs are rated by ‘grain’, from the coarsest at 1 to the finest at 15 grain. Photo 6 compares a few Auriou grains.

Rifflers

These are very handy for woodworkers because they allow for shaping of details such as own-made furniture handles, and they are pretty well essential for carvers. They can be either file or rasp cut and have a different grade of cut at each end of the steel between which serves as the handle (photo 5). I know carvers who refer to their riffler files as their most used tools. Not surprisingly you can expect cheap rifflers to leave a rough surface.

Care and storage

Understanding that these are cutting tools should inform the way you use and store them. The steel has been hardened in order to increase the life of the cutting edge but the trade-off is that this also makes them brittle. So slinging these tools into a drawer or toolbox where they can bang into other tools will quickly reduce their effectiveness. Files and rasps need to be stored in the same way as chisels and carving gouges, individually hung or separated by dividers in a drawer or toolbox.

I like to have a carpet tile on the bench where I put the tools I’m using. Not only does placing cutting tools on carpet reduce the chance of edge damage but I find it also makes me pay attention to the process I’m engaged in, and zen some.

Usage

Rasps and files are designed to cut only on the push stroke. Dragging them backward over the workpiece will cause unnecessary wear and edge damage, and won’t improve the finish on the job either.

Although man-made boards such as MDF are easy enough to shape with cutting tools they are murder on even high carbon steel and will rapidly reduce the life of rasps and files. As this means replacing rather than sharpening when they get uselessly dull it makes sense to use only bargain bin files on MDF and the like.

The brittleness of the steel makes it dangerous, for both you and the tool, to use it as a hammer or lever. Certainly it is very easy to snap the finer tools such as Swiss pattern needle files and rifflers like those shown in photo 5. The size of the teeth means there is only so much the file or rasp can remove with each stroke, so excessive pressure is futile as well as risky for the tool.

Cleaning teeth

The teeth can become clogged in use and need routine cleaning in order to keep cutting effectively. Soft metals like brass and aluminium will quickly choke up fine file teeth and again support the ‘harder the metal the finer the file’ theory.

File cards with stiff steel wire bristles are often recommended for cleaning files but I prefer to be a little kinder on the edges and use a brass brush. Sometimes a file will get pinned; that is to say metal jams so tightly in file teeth you have no choice but to use a narrow strip of brass or copper to individually lift these lumps.

Michel Auriou of that family’s rasp company recommends using a stiff but non-metal bristled brush to clean their tools.

Rubbing file teeth with chalk while working metal is an old trick for keeping the teeth easy to clean. Compressed air usually works to remove wood, especially if you clean up promptly so the waste doesn’t get compacted and then harden in the gullets. But whichever method you use you do need to do it regularly as you work. This is because material jammed in the teeth can drag over the surface and mark it, as well as reduce the efficacy.

And while we’re on the topic of cleaning teeth I’ll mention a good use for your old toothbrush. Rust is the mortal enemy of steel cutting edges and your sweat is a good starter for it. If you rub that old toothbrush with paraffin wax and then scrub your clean file or rasp you’ll leave just a trace of wax to prevent rust. And if you warm the tool in the sun beforehand the wax will spread, and penetrate the steel better. And the toothbrush will feel fine about continuing to prevent decay.

Which tool?

Everyone has different requirements of course, but here are some tools which have been useful to me over the years, starting with files. If I did more work with metal I would certainly enlarge the range but this is a good basic kit. I know there are those who’ll get indignant at my using any one file for more than one material, but that’s just how it is in my shed.

Files

A 10" half round bastard cut is about as aggressive as I need to get with metal.  More than that calls for the angle grinder as far as I’m concerned. It’s also open enough to shift wood without choking too badly. The 8" half round second cut is also a double cut file but less aggressive. It needs constant clearing when working wood but improves a roughly shaped surface.

Mill files are single cut and give a smoother finish. I am glad to have both an 8" and a 4" smooth. They tune hardware and other tools. A smooth mill file is a good tool for truing the edges of a cabinet scraper for example. An even finer finish is attained by draw filing. This refers to using the file at right angles to the cutting stroke—remembering of course to use the cutting pressure in the appropriate direction.

The round (aka rat tail) files don’t get regular work but are essential when required. An 8" second cut and a 6" smooth gets me by. In my shed they are probably used more for wood than for metal but I think that may be about to change now that good rasps will be more readily available.

A warding file is slim and pointed and really handy from time to time. Nice for the mouth of a plane for example, as well as for adjusting hardware. I have a 6" smooth.

Rasps

7. Detail of machine cut rasp

Now here is where many woodworkers are really missing out. The teeth of rasps are supposed to be randomly distributed but machine cut rasps sometimes have regular rows of teeth which will leave furrows because each tooth follows directly in the track of those before it (photo 7).

8. Surfaces created by a bastard file (left) and #49 patternmakers rasp

If rasps have seemed crude tools to you it may be that you had a badly made one, or simply that you were using too coarse a cut. Photo 8 compares the cut of a bastard rasp with the cut of a patternmakers rasp.

When I first encountered a patternmakers rasp it was a revelation. It cut rather than tore the surface. The price was a surprise—way back they cost me over $100 each—but I’ve always been glad I bought them. The American company Nicholson used to stock a good range but now only carry the #49 and #50 with the #50 giving the smoother finish. They are machine cut but with randomly stitched teeth for a good finish. Lovely tools for shaping, especially when blade tools such as a spokeshave would have problems with grain.

9. Auriou hand cut rasps

For decades I had heard about finer handmade rasps, but they weren’t available locally and like many woodworkers I didn’t get around to buying them from overseas, largely because I thought I was doing okay without. However, that is about to change as there is at last a distributor for Auriou rasps in Australia and I have had a chance to use a selection of them (photo 9).

Auriou is a family company in France which has been making rasps, by hand, since 1857 in a range of shapes and grades. A small selection of these is now carried by Lie Nielsen Australia. There are other European brands of handmade rasps, but I’m referring to Auriou because they are good quality and are now available here.

10. Nicholson (top) and Auriou rasps perform well yet have significant differences.

There are significant differences between Auriou and Nicholson rasps as can be seen in photo 10. The teeth of the Auriou go right to the edge which allows you to rasp into corners. Compare this with the edge of the Nicholson. Note also that the Nicholson has a docked end whereas the point of the Auriou enables getting into tight spaces. For me these are good reasons to recommend the Auriou, even though if there is a difference between the results from the machine punched Nicholson and the handmade Auriou of equivalent grade I couldn’t pick it. The really big point in their favour is the wide range which includes fine rasps that give the sort of finish you would otherwise need a file or sandpaper to achieve.

11. Showing the different surfaces produced by 8 grain and 15 grain Auriou rasps

Photo 11 compares the surface left by the 8 grain and 15 grain rasps and shows how clean a finish you can get from a rasp. The wood is 20mm thick blackwood, chosen for its firm but open grain to highlight any tearing by the rasps.

As for which rasps you most need, I am planning to supplement my #49 and #50 Nicholson patternmakers rasps with some of the Auriou range, starting with the 6” 15 grain, the finest cut, and their 8” 11 grain rat tail. But I don’t imagine I’ll stop there.

Hopefully you will look at rasps and files in a new light, and consider adding to your choices. Being able to rely on a good selection of good rasps and files is a truly life enhancing condition for all woodworkers.

First published in AWR#56, September 2007

Richard Vaughan is a Brisbane based designer maker who also teaches woodwork classes. See richardvaughan.com.au