J-Weight Sanding Belts Explained 

An important factor when working with sanding belts is not only the right abrasive grain, but also the material of the backing. The thickness of the backing is equally as important as well. When you use the correct backing and thickness, you will notice a great outcome and a substantially longer life span. When you try to use the wrong backing material or thickness, you can lead your workpiece in the wrong direction as you will notice unwanted complications such as tearing or burning of the material. 

Thickness

When talking about thickness, there is an alphabet scale that will help you determine which one is best for you and your job. Keep in mind that A weights are more flexible, whereas Y weights will be a lot more strong. Also, A weights through F weights all have a paper backing. First we have the A and B weights which are most commonly used for fine wood finishes and when you are using your hands to sand rather than a tool. We then have C and D weights which are also used with hand sanding, but you can also use it on a power sander of a smaller size. Next, we have E and F weights which are most commonly used for belts, discs, and sanding rolls. They are great for more aggressive uses because they do not tear easily. X and Y weights are used for metals and metalworking. While the X weight usually has a cloth backing, the Y weight is mainly synthetic -- the X weight is more flexible, whereas the Y weights are better for a more harsh job.

J-weight

J weights consist of a cloth backing and they are sturdy and durable. J weights are also flexible and can maneuver around rounder surfaces and edges -- for example, a knife handle -- which makes it a popular purchase item. J weight belts will give a nice and even finish to your workpiece. Remember to avoid using J weight belts if you are not using a rotational platen attachment or when slack grinding. Not only is J weight good for knives and knifemaking, but they are also great for plastics, woods, and surfaces that are painted.