Files and Rasps

Files & Rasps
 
Files and rasps are handy tools when it comes to smoothing and shaping. While some people use the terms interchangeably, there are distinct differences between files and rasps and each serves a different purpose. It is a common perception that files are best suited to metal applications while rasps are used only for wood, but this is not necessarily the case. In general, rasps are used for more aggressive work while files offer a slightly more refined finish. Of course, your selection will also depend on what grade and material you are working with and other factors as well. The large selection of available options can be a little intimidating, so consider the following questions as you seek to determine what file or rasp is right for you:
 
          • What types of files are available?
          • What types of rasps are available?
          • What shapes do files and rasps come in?
          • What do different grades indicate?
          • What special features might be helpful?
 

Files, Rasps, Shapes, Grades and Usage


Choosing the right file or rasp depends largely on what material you're working with and how fine of a finish you need. In most cases, files and rasps serve as an intermediary step between rough sawing and finishing with sandpaper. Files and rasps can be used on wood, metal and plastic and may be used to sharpen mower blades and other tools, remove rust, deburr metal and more. Along with choosing a tool that has the best grade and configuration for the material you're working with, using the proper technique and keeping your tools clean during use is crucial to getting the job done right.
 
Files: Files are characterized by parallel, diagonal rows of teeth that form ridges across the surface. Each of the sides is either cut, meaning that it has teeth, or uncut, meaning that it is smooth. Single-cut files have one set of teeth and are used to provide a somewhat smoother finish or create a sharp edge on knives, shears or saws. Double-cut files feature a second set of teeth that cut in the opposite direction and are used for more aggressive filing, shaping or removing rust from metal and smoothing wood. Curved-cut files are used for a variety of automotive applications, such as smoothing body panels. Rasp-cut files feature a series of individual teeth and are used primarily on wood. File lengths can range anywhere from 4" to 16" or longer and are usually available in increments of 2". 
 
          • Uncut edges are also called safe edges
          • Use light pressure when working with single-cut files
          • Use heavier pressure when working with double-cut files  
          • Curved-cut files feature curved contours across the face of the file
          • Curved-cut files can also be used for working with plaster and fiberglass
 
Rasps: Unlike files, rasps have individual teeth that are often randomly placed to provide a faster, rougher cut. Use them to remove material quickly, particularly when working with wood. Wood rasps have a very coarse surface and are used primarily for quick removal of stock. Cabinet rasps come in handy for finer, more delicate work, such as creating a proper fit for mortise or tenon joints. Rasps tend to clog less frequently than files because of the way the teeth are designed and spaced.
 
           • Horse rasps are used for working on horseshoes
           • Patternmaker's cabinet rasps provide a smoother finish
           • Cabinet rasps can be used on wood of all types, leather or soft metals
         
Shapes: Files and rasps come in several different shapes, each of which offers a unique set of advantages for different tasks. The chart below describes the most common shapes as well as what activities they're best suited for.
 

Shape

Description

Uses

Flat, Mill or Hand Features straight edges and a flat surface with a series of parallel teeth.  • General tasks
• Flat files taper in width and thickness from the
  middle outward
• Mill files taper in width and thickness all the way
  through
• Hand files taper only in thickness and feature a
  square point
Half-Round Features both a flat face and a curved face. • Concave surfaces, edges and holes
• Flat face can be used for filing flat surfaces
• Curved face is ideal for use on grooves
Round Circular design features teeth all the way around. Also called "rat-tail." • Enlarging round openings
• Removing burrs from metal
Square Features four cut sides. • Enlarging rectangular openings
Triangle Features two cut sides and one uncut side. Also called "taper" or "threesquare" • Working on acute internal angles
• Squaring corners
• Filing grooves
• Sharpening saw teeth and other tools

Grades: Files and rasps are both available in varying grades, or levels, of coarseness. File grades are often broken down into bastard cut, second cut or smooth cut. Bastard cut is the coarsest grade and is used to remove material quickly. Second cut can also be used for fast removal, though it provides a slightly smoother finish. Smooth cut features a fine grade that's ideal for finishing work and preparing surfaces for sanding. Rasps also come in a variety of grades, including bastard, cabinet and wood. In their case, however, bastard is the finest grade, with cabinet and wood rasps providing a coarser finish.
 
          • In general, larger files and rasps are coarser than smaller ones, even if they have the same grade
          • Second cut is sometimes referred to as medium cut
          • Cabinet cut is sometimes referred to as medium cut as well
          • Cabinet- and wood-grade rasps remove material quickly
 
Usage and Care: As with all tools, proper care and technique is the key to safe and effective use. Choose the right combination of shape, size and grade for the project you're working on. When filing or rasping, push outward across the surface with a level of pressure appropriate for the material you're working with. Lift the tool at the end of the stroke and bring it back to the starting position before allowing it to touch the surface again. Working in only one direction will provide a higher quality finish and prevent the teeth from dulling too quickly. After a while, files will become clogged. Cleaning them with a wire brush or file card will help keep them in working order.
 
          • Work in a well-ventilated area and use respiratory protection if necessary
          • Rubbing chalk on the surface of a file or rasp can help prevent clogging
          • Keep files in protective sleeves or slotted racks to prevent them from scraping against each other when 
            not in use
 

Features


Handles: In most cases, rasps and files do not come with handles. Holding onto the bare tang can be uncomfortable, so you'll need to purchase a handle for each one. Look for ergonomic handles with rubberized grips to provide greater comfort. You can also purchase a universal handle, which features inserts that allow it to be used with different shapes.
 
4-in-1 Tool: For maximum versatility, look for a multifaceted tool that allows you to tackle a number of different tasks. Some files are designed with both round and flat surfaces and with two different ends, one of which is a file while the other is a rasp.
 
File Card: Keeping files and rasps clean is one of the keys to ensuring high-quality work. A file card is designed to get in between the teeth to clean out sawdust, metal shavings and other debris to keep your tools in proper working order.
 
Diamond File: These files feature ground diamond particles, making them well suited to industrial applications. Use them when working on fiberglass, epoxy and other hard surfaces. Smaller diamond files will work well on glass, ceramic and various metals.