Rasps And Files: Shape And Smooth More (And Sand Less) With These Simple Tools.

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This article is from Issue 55 of Woodcraft Magazine.

Shape and smooth more (and sand less) with these simple tools.

By Craig Bentzley

For years, I’ve regarded my rasps and files as my not-so-secret secret weapons. Hidden in plain sight beside my workbench, my collection has never generated a single comment from any visitor. Admittedly, these simple steel-toothed tools lack the romance of my planes, handsaws, and chisels, but what they lack in allure, they make up for in function.

Truth be told, files and rasps rank among my most reached-for tools because they’re quick and efficient to use. Whether the job calls for heavy stock removal, erasing tool marks, refining curves, taming tear-out, fitting a metal part, or even repairing some other tool, there’s a file or rasp that can get the job done. 

These simple shapers and smoothers require a bit of skill to use effectively, but as you’ll soon see, the learning curve is surprisingly short. And unlike most other hand tools, files and rasps come ready to work fresh out of the package. The biggest hurdle to using these tools may be selecting the right ones.

Read on to learn what’s available and how you can make these toothy tools work for you. As a wrap-up, I’ll provide you with a starter set that can be put to immediate use in almost every workshop.

Feed the rasp simultaneously down and across the work. Try to use the full length of the tool to wear the teeth evenly.

Rasps

Easily identified by their prominent triangular teeth, rasps excel at initial shaping and sculpting operations on wood. Unlike other shaping tools, such as drawknives and spokeshaves, rasps won’t tear out material where the grain changes direction or if the stock is highly figured.

sing a rasp is fairly intuitive, but a few tips can help you achieve faster cuts and smoother surfaces. When using a rasp, start by making a few light test strokes to determine the preferred angle of attack. (This is especially true with hand-stitched rasps. Many are designed for right- or left-hand use only.) Then, use long, continuous passes at approximately a 45° angle, simultaneously feeding down and across the work, as shown in Photo A. Let the tool do the work; a sharp rasp should not require much pressure to cut. (In contrast, a dull rasp will skip across the workpiece.)

General-purpose rasp ($10 - $15)

Grobet Patternmaker’s rasp ($90)

Hand-stitched Cabinetmaker’s rasp ($110)

Better machine- and hand-stitched rasps cut quicker and produce smoother surfaces than a visibly coarser, low-cost rasp.

With rasps, as with other hand tools, you get what you pay for (see Photo B, below). Generic general-purpose wood rasps, sometimes referred to as “cabinet” rasps, have uniform rows of teeth that leave a fairly ragged surface in their wake. The poor cut quality can require considerable cleanup.

Better quality rasps are labeled as “patternmaker’s” or “cabinetmaker’s” rasps. These tools sport staggered teeth that leave a much smoother surface than general-purpose rasps. Patternmaker’s rasps can be machine-made or hand-stitched. As you might expect, the priciest hand-stitched rasps require the least amount of cleanup.

Files for working wood

Files are used to refine the rasped surfaces, but they can also serve as stand-alone shaping tools. For most woodworking chores, I use fairly coarse files, like the ones shown at left. With most files, tooth size is proportional to tool length; the longer the tool, the larger the teeth. I find the 6"- and 8"- long round files are most useful in the woodshop, as the 10" is a bit too aggressive. When it comes to flat and half-round files, I find the 8" and 10" long double-cut bastard files best for woodworking. (Because the teeth on shorter, finer-cutting files quickly clog with sawdust, I reserve them for metalworking.)

Files cut on the push stroke, but how you feed the tool across the work can influence the cutting speed and quality. Feeding the tool down and diagonally across the wood, as done with a rasp, is suitable for general shaping and fairing. For rougher shaping (Photo C), you can feed the file perpendicularly across the work, which is called “cross-filing.” For a smoother surface, run the file parallel with the grain, called “draw-filing” (Photo D).

10" half-round coarse wood file
6", 8" & 10" round files
Cross-filing removes stock quickly, but leaves a rough surface and may create some chip-out at the back of the cut.
Draw-filing is slower, but produces a smoother surface.

Clean Your Teeth

A file card is a must-have accessory. Use the nylon bristle side to clean rasps and the wire bristle side to clean files. You can use a metal pick or finishing nail to clean stubborn debris from file teeth, but any metal–even brass bristles–will eventually dull your rasp’s teeth.

Files for working metal

As we all know, woodworkers often work with metal as well as wood. Files can do double-duty, but I find that once a file is used on metal, it doesn’t perform as well as on wood anymore. For that reason, I suggest investing in a separate set of files for metal work.

Metal files are available in two types of tooth configurations: single-cut and double-cut (see photo at right). Single-cut files have a single set of parallel teeth. Double-cut files have a second, opposing set of teeth that create a diamond pattern. I prefer using single-cut files for straightening and refining critical metal surfaces. When I need to remove a lot of metal during initial rough shaping or fitting, I’ll start with a double-cut file and then follow up with a single-cut file for the finished surface.

In addition, there are three tooth sizes: bastard (coarsest), second-cut, and smooth (finest). You can shop around for shorter files with larger teeth, but in most stores, the in-stock files are sold in common-size tooth combinations. (See the “File and Rasp Starter Set” page 41 for specific recommendations.)

Single-Cut
Double-Cut

Metal Working for Woodworkers

Using a straight-filing motion quickly reestablishes a straight edge on a cabinet scraper.

A mill file is suitable for cleanup and general shaping, such as softening sharp edges and removing nicks from a plane sole.

Use a small, round chainsaw file to quickly shape curved metal parts, such as beading blades for a scratch stock.

Capable of fitting into tight spots, needle files can be used to shape and smooth ragged edges, such as those on rough-cast hardware.

Rifflers aren’t the fastest cutting tools, but they offer a precise way to clean up ragged edges in tight areas.

Rifflers

Rifflers are slim, double-ended tools curved to opposing shapes. They are well-suited for getting into tight areas and doing detail work or cleaning up carvings. They are sold in a wide variety of configurations, including flat, round, half-round, and triangular. (Rifflers are available with either file or rasp teeth. I prefer the files, as I find rasp-rifflers a tad too aggressive.)

To use a riffler, hold the tool like a pencil, apply pressure with the finger of your other hand, and work in back-and-forth strokes. Admittedly, riffler work can be tedious. Because the cutting face is small, the work goes slowly and the teeth clog quickly. However, for their ability to erase the tool marks out of reach of larger tools, they earn their keep in my shop.

Iwasaki Files

A fairly new entry into the world of wood shaping tools, Iwasaki files deserve special mention. Although technically files, these tools cut as aggressively as rasps and still produce super-smooth surfaces. The secret is in the cutting edges. The milled, chemically etched teeth shear materials, producing shavings instead of dust. In addition, the diagonally-cut groove pattern helps eject material before it clogs the teeth–working much like miniature chipbreakers. (They’re good for wood and plastic, but don’t even think of using them on metal.)

With sharp teeth that cut fast and leave a smooth surface, Iwasaki files can serve as a single-tool stand-in for files and rasps.

Iwasaki files are available in a wide range of sizes and configurations (see woodcraft.com). All of the profiles have “safe” (tooth-free) edges, allowing them to work up against adjacent surfaces without scarring them. These files haven’t yet bumped any tools from my must-have starter set, but they are an attractive, affordable option for woodworkers saving for a hand-stitched rasp.

Protect yourself and your tools

You’ll want to make or buy handles to protect your hands from injury when handling these tools. Auxiliary handles are sold for grasping the tool at its far end, but a wrap of masking tape will also do the job.

To protect your rasps, files, and rifflers, store them in a rack or tool roll to prevent the edges from banging together. Rust can also contribute to premature dulling. For long-term storage, consider using a sealed tool box with a VCI (vapor corrosion inhibitor) inside. Oils and other dust-collecting lubricants should not be used because the teeth will load up more readily and require more frequent cleaning.

File and Rasp Starter Set

Considering the different sizes and tooth configurations of files and rasps, selecting a starter set for shaping and smoothing can be downright dizzying, but don’t fret. You can build a decent starter set for about as much as you’ll pay for a single premium hand plane. Here’s a list of my go-to tools.



1. Patternmaker’s rasp ($90)

A quality patternmaker’s rasp is an investment. Buy the best tool you can afford, take care of it, and it will tackle all sorts of shaping and sculpting chores for years to come. Rasps are available in flat, half-round, and round configurations. I find that a half-round rasp is the most useful.



2. 8" single-cut bastard round file ($5)

Good for getting into tight radii and enlarging holes on woodworking projects. Consider buying a second for metalworking chores, such as filing curved scraper blades and fitting hardware.



3. 10" half-round coarse wood file ($25)

Although typically used after initial shaping with a patternmaker’s rasp, this file can serve as a stand-alone shaping tool for light-duty work.



4. 8" double-cut bastard half-round file ($8)

I often use this file to clean up surfaces after working on them with a 10" file, but it can also be used for general metal-shaping chores.



5. 10" single-cut bastard mill file ($8)

Although this is my go-to tool for truing up edges on cabinet scrapers and performing other metalworking jobs, it is equally handy for a host of wood-shaping chores, so buy two.



6. 3⁄32" diameter × 8"-long chainsaw file ($5)

This slim file is perfect for smaller metal-shaping chores, such as creating scratch stock and molding plane blades. It’s also handy for cleaning up the edges of metal hardware and machinery.



7. Needle file set ($25)

These super-small files are indispensable for intricate shaping and cleanup of both metal and wood, including the smoothing of scrollsawn edges.

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