The die grinder is the smallest of the various types of grinders that are made. Unlike the larger grinders, these are not intended for rough-cutting as much as they are designed for detail-oriented work. Their high speed and variety of tips make them an ideal tool from fine finishing of a workpiece to adding details to the shape by hand.
Die grinders depend upon high speed for their cutting power rather than brute force. These tools are typically low power units, 1/3 HP or less. However, they run at speeds of 20,000 RPM or more with a few units that top 50,000 RPM. At those high speeds, it’s easier to do the fine detail work these tools are known for.
Options Available for Die Grinders
These tools are rather simple, without a lot of options to choose from. The options actually come about in the type of tip you put on the die grinder. However, there are some things you might want to consider when looking for a die grinder.
Die Grinder vs. Cutoff Tool
Die grinders are often sold as cutoff tools with the addition of a guard and the installation of a fibrous cutoff wheel. With a cut-off wheel, a die grinder can be used to cut metal bar stock and tubing. If you buy a die grinder, rather than a cutoff tool, you can easily convert it for cutting off metal bar stock and tubing by adding a shield to protect you from hot metal sparks. The only difference between a die grinder and a cut-off tool is this shield.
For this reason, you might want to consider buying a cutoff tool rather than a die grinder because that way you already have the shield. Just verify the tool comes with a 1/4" collet and that its speed is equal to the die grinder.
Variable Speed Control
Many die grinders are designed to allow the user to control the speed, even though they’re typically used at full speed. However, when cutting or grinding softer materials the variable speed helps prevent overcutting and potential destruction of the workpiece.
Straight vs. Right-Angle
Traditional die grinders are straight, with the tool rotating perpendicular to the length of the tool. More recently, manufacturers have started making right-angle die grinders and even one manufacturer is making a die grinder built at 30 degrees. While the angled head is easier to hold for some types of operations, both styles have their place.
These angled die grinders shouldn’t be confused with angle grinders which operate totally differently. A right-angle grinder only works with grinding wheels that mount to a shaft. A right-angle die grinder still has a collet for the various types of tips to mount into.
Pneumatic or Cordless
As with many other power tools, cordless die grinders are now appearing on the market, for portability and ease of use. While cordless die grinders are longer than pneumatic ones, not having to drag around an air hose or power cord makes it possible to get into areas where pneumatic die grinders simply can’t reach.
Like most cordless tools, cordless die grinders are used more by contractors on remote job sites, than by people working in a shop. The advantage of working off of battery power isn’t as apparent when you are in a shop with airpower piped throughout. Pneumatic die grinders will run virtually indefinitely off of shop air as they use very little air. In the same situation, a cordless die grinder would require stopping to change the battery periodically.
Pencil Grinders
A sub-category of die grinders is pencil grinders. These are designed using a 1/8" collet, rather than a 1/4" one. The smaller collet allows for smaller cutting heads for finder detailed work. Typically these will be smaller, making them easier to hold like a pencil and use in the same way.
Pencil grinders come in pneumatic, electric and cordless. The electric ones may have the motor separate from the grinder head, running power through a flexible cable down to the head. This "flexible shaft" pencil grinder is popular with model makers and jewelry makers who need to do fine detail work without having a large motor-driven tool in their hands.
The Dremel tool actually falls into this category although it has a larger body. Nevertheless, it comes with a 1/8" collet designed to be used with the same types of tips used on other pencil grinders. Even though it’s larger in diameter, the casing is designed to be ergonomic so it can still be held like a pen and used as easily as the other types of pencil grinders.