A belt grinder might seem like a simple piece of equipment, but in fact, it has a lot of control issues that an untrained user can end up destroying any perfectly made component whether it’s wood or metal.
Essentially, the belt grinder is the big daddy of sanding tools and as I started out by saying, this is the best tool to destroy any project, or to speed it up.
Belt grinders are an essential carpenter and blade maker’s tool, and is used in both industries for securing a fast solution for either leveling surfaces, freehand rounding or shaping as well as sharpen metal blades. While grinding belts can be and are used for metal, I will focus on wood applications in this article.
There are many types of belts to choose, from course wood grade belts to fine metal grade belts. The belt size is machine dependent, so what is important is not the belt size which must fit a specific machine, but the fine to coarse grain size and material you pick (see more at Mechanic Guides).
For basic wood work, you want to pick any belt between 80 to 120 grit. For coarse grinding, which is really not for everyone, a 50 grit, and anything under will leave deep grooves. For fine sanding, start out with a rough grit like 50, move up to the 80 then go to 100 and then take on the 120, don’t jump directly from 50 to 120. Personally, I like to have a set from 40 up to 600, that way I cover all my options for wood, metal and even ceramic applications.
The traditional grinding material is aluminum oxide. These come in a number of qualities, where the khaki color signifies a disposable belt, and a dark brown belt is a premium long lasting belt.
There are also “planer” belts, which are bright blue and are made of Zirconia. These are long lasting, have sharper and tougher cutting particles and are more aggressive. However, Zirconia belts are the more expensive models to buy.
Don’t Mix materials
If you sand wood and have a large sawdust collection bag, do not sand metal. Metal will create sparks, and this leads to an instant fire hazard. If you want to work both materials, make sure you clean up the sawdust before you sand metal.
Most grinders come with a pre-set direction or preferred direction of operation. This is marked usually by an arrow, as such, non-directional belts can be installed either way. You will need to track the belt; this means keep the belt centered on the roller. You can adjust the belt by using the tracker knob with aligns the rollers so that the belt doesn’t wander off the roller while in operation.
The more advanced grinders come with pre-set speeds, and this allows you to toggle between slow to fast sanding for different applications.
Sawdust is the by-product of grinders, (Sanders too). However belt grinders are notorious for making a lot of sawdust. As such, all the best models come with some form of dust collection that involves a vacuum unit, a bag, and some tubing. If your model doesn’t have one built in, buy one before you use the grinder, or you will end up in a very dusty, dangerous and unhealthy environment.
Buy a belt grinder that has variable speed and is large enough for the work you want to perform. Make sure there is a large cut-off switch and preferably get one with a minimum 2 HP motor for 2” models, a 4-5 HP for 3” models.
Make sure you have a dust collection accessory, preferably a vacuum unit that sucks up the grinder dust as it appears, and these are must-have additions for both safety and health.