An angle grinder is a handy tool to have around to use for grinding, polishing, cutting, and a number of other tasks that call for abrasion. Some people may not happen to have an angle grinder just lying around, however, but fortunately, there are a number of tools you can use in place of it that will get you the same results. The replacement tool you use depends on the job you need to accomplish, and of course, what you have available.
An angle grinder is basically a drill assembled differently, with different angles of approach, and as such, a simple drill can serve as a replacement for one more often than not. The amount of head attachments available for drills ensures there will almost always be one for the purpose you need. You can buy sanding and polishing attachments for more delicate surfaces that require more care, and wire heads for less abrasive, cleaning projects.
You can get cutting attachments for jobs where you actually need to cut something, and grinding attachments for times when a more abrasive head is required, such as smoothing the surface of the corner you just cut. Take a look around your hardware store, and odds are good that you will find the type of attachment you need there.
Similar to plain drills, the Dremel is a versatile rotary tool that can easily replace an angle grinder for many jobs. They have many of the same choices for head attachments as drills (since they are, after all, miniature drills themselves), and even more, including cutting, drilling, polishing, grinding attachments, and more, except on a smaller scale. An angle grinder is quite a large tool, relatively speaking, so for jobs that have limited space or tight areas, or where only a small quantity of work which needs done, a Dremel may be the best choice.
For polishing or sanding jobs you have, a sander will work fine as a replacement. The range of sandpaper available varies from extremely fine to hard and coarse, and there are polishing attachments kits you can get at any hardware store. Grinding kits that use more abrasive materials than sandpaper are also available. A sander is a good choice if you have a large, flat area that needs smoothing or polishing, and they are also good for sharp corners. They are also comfortable and relatively cheap.
Despite some misconceptions, not every job requires a power tool to be completed. You can go a long way using plain, old fashioned elbow grease along with a number of hand tools. You can use a hack saw for smaller jobs where metal needs to be cut. Many different varieties of wire brushes are available in all sizes for whatever job you need, and they do a good job smoothing and wearing down sharp edges and burrs on metal. Sandpaper by itself is handy for spot polishing and touching up, though be prepared to go through a lot if you have a more demanding job.