Which files should I buy?
New notchers / notching for yourself: Buy a set of diamond files in a variety of grits. 120-600 are most common; some go up to 1200 for finishing. Sets can be found on Amazon / Ebay for ~$10. The sets below are are a few examples of available options - depending on individual preference and method, you may prefer different sets, file shapes, or grits (this is not an exhaustive list!)
- Variety diamond file set, 180-320 grit in various shapes - Good all-around starter set
- 120 grit diamond file set, various shapes - Low grit number; removes lots of material relatively quickly
- 40-600 grit diamond file set, rectangular - Wide range of grit values, but relatively thick and only one shape
Veteran notchers & vendors: Diamond files will still work OK - but you should definitely try some quality steel needle files from either Nicholson or Grobet. They cut quicker / cleaner and will last much longer than diamond files (which “wear out” by gumming up with plastic). Unfortunately, good steel files are also ~$15 each. If you do try them out, I recommend the #2 and #4 finishes (#0 and #6 are optional). Higher number = finer finish.
- Various Nicholson 6 1/4” needle files (#0, #2, and #4) - Choose desired shape and finish. 1/8” dia. handle
- Nicholson 6 1/4” tapered half-round #6 needle file - McMaster doesn’t carry #6 files so you’ll have to hunt around. Search results aren’t that reliable - pay close attention to the length, shape, and finish.
- PFERD wooden needle file handle (optional) - Note: This ONLY fits files with 1/8” dia. handle. If you buy different files, measure them before ordering handles to ensure a proper fit. A handle changes the weight balance - some prefer not to use them.
Files: A Comparison
Looking at the surface of a file under magnification tells you quite a bit about its quality. Even a quick glance exposes the flaws of the cheap steel files (“Amazon Lime Green Set”). Even brand new they already have pits and voids, the cutting teeth are poorly formed (many are already damaged or broken off), and the surface itself is bumpy and irregular. The Nicholson files are completely the opposite - extremely consistent and well-formed cutting features (the blemishes you do see are just little bits of dust/dirt that settled in the teeth).
Beyond the file surface, the quality of the steel plays a huge role in the performance of a file. Cheap, generic files often use low-quality steel alloys with poor heat treatments (don’t be surprised if your file wears down faster than the material you’re filing!). Reputable file makers use quality steel alloys and tightly-controlled heat treatment processes, resulting in very hard, durable, and long-lasting files.
Diamond Files:
Diamond files are inexpensive to manufacture - think of them like rigid strips of sandpaper. They file via abrasion - lower grits don’t give uniform results and tend leave scratches behind, so high grits are needed to achieve a good surface finish. Their primary industrial use is for very hard materials such as stone, ceramic, glass, and hardened steel - materials that can’t be filed by other means, and which which chip away when filed (i.e. they don’t get stuck in the file itself). Plastic is actually very problematic for diamond files - it easily sticks to the file surface and gums up the abrasive, significantly reducing both cut quality and speed. However, these generally still produce better results than cheap steel files.
Steel Files:
Quality steel files are expensive to produce. They file via cutting - each tiny metal tooth slices its own bit of material away. They produce very clean and uniform cuts - the highly-regular grid results in a consistent surface finish without scratching. Plastic doesn’t gum up steel files as it does with diamond files, and any residual plastic that does stay behind can be cleaned away with a file card. When filing a plastic edge, start with the file at a very shallow angle (almost parallel with one surface). Make a few strokes, tilt the file up to a more extreme angle, and make a few more strokes. Continue this process around the edge until the file is almost parallel with the opposite surface. A plastic burr will be produced as you go. It will look a bit messy at the shallow angles, but the burr will cleanly cut away as you reach the final angles, leaving behind a smooth, clean surface.
Tips for using steel files:
Only apply pressure on the “push” cut (moving in the direction of the file tip). File teeth are angled and only cut in one direction. Applying pressure on the “pull” cut won’t help and with harder materials can actually bend / damage the file teeth.
Practice your technique. Removing a lot of material (i.e. filing octagon notches) is pretty easy… just point the file through the hole and make a lot of strokes. Great surface finish & nicely rounded edges take a bit of practice. Start with the file at a very shallow angle (almost parallel to the material) and make a few light strokes. Tilt the file forwards a bit; take a few more strokes; tilt forward; take strokes; and so on until you are almost parallel with the opposite surface. A small, ugly “burr” of plastic will start to appear but will fall off with the final, steepest strokes.
Pay attention to your pressure, and don't press too hard! Steel files don't need as much pressure as diamond files! Too much pressure will cause the file to bite into the material rather than slicing through it. This can scar the material, leave deep scratches, guide the file off-course, and/or result in poor finish overall. Especially with very fine files, just the weight of the file itself is enough!
For long edges, slide the file sideways as you stroke forwards. You can file long edges very quickly with this method.
Vary the file angle BETWEEN strokes, not DURING strokes. It's much harder to apply the right pressure (and get consistent results) if you're trying to turn the file partway through each stroke.
Play around with the different file sides and edges. Different sides often have different cut patterns to cut faster (double-cut) or finer (single-cut).
If needed, clean your file with a small brass wire brush. Don't brush in the direction the file teeth cut as this will dull them.
Needle Files Comparison Video:
Credit: “Catus Maximus” on Youtube