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How Do I Properly Sand With A Wide Belt?

April 26, 2023

How Do I Properly Sand With a Wide Belt?

Running into issues when sanding with a wide belt can cause frustration and make you feel defeated. It can also be hard to identify what is going wrong when you meet these issues – whether it is chatter, loading, burn marks, etc. Essentially, when you face problems when sanding, it is usually due to improper sanding, machine issues, or the belt itself. There are ways to solve these issues and we will go over them in this article. 

Why is My Belt Leaving Chatter Marks on My Workpiece?

You may be wondering, “What are chatter marks?” Chatter marks are the unwanted lines that appear across the surface when sanding. If you realize that chatter marks are appearing on your workpiece, it often is the machine that is cueing that, rather than the belt. 

Several things that can solve your issue are checking the following: contact roller, pressure/tension, the belt joint, grit sequence, or the conveyor belt. For the contact roller, it is important to use the correct roller for your application – for example, metal or hard durometer rollers should only be used for stock removal. If you are using the right contact roller, check to see if it is worn out or out of balance. Tension pressure can be a factor of chatter as well. Making sure the psi is set correctly is ideal. Cloth belts use 55 - 65 psi, paper should use 45 - 55 psi, and polyester should be 65 - 85 psi. The correct belt joint is going to help massively as well – make sure the tape is not too thick for your application. The grit sequence for stock removal is important too. Using the wrong grit size or skipping more than one grit is going to lead to even more issues. Lastly, the conveyor belt. A worn out conveyor belt can also be one of the reasons chatter is occurring. Clean and remove any dust and debris buildup to ensure a smooth ride.

Tip; To find out whether the chatter marks are from the roller or the joint, these equations can help you determine where the problem is coming from. 

Why is my Belt Sander Leaving Me with a Wavy Surface?

A wavy surface is not ideal when sanding. This could be coming from the combination of grits, the belt, or the platen. We have already gone over never skipping more than one grit, but it is also important to pick the right grits for the application you are using. We have another article that goes over all the things you need to know about grit sequence and which one is most suitable for you. Changing your belt can help avoid a wavy surface if the belt itself is too loaded with debris or if you have gone a long time without changing it. Since platens are usually used for finishing – using it to remove stock can lead to an uneven surface. If the pad you are using is too flexible or you applied too high of a pressure, this can also cause a wavy and uneven work surface. 

Why Do I Get Ridges and Raised Lines when Sanding?

There are numerous patterns that can appear on your work surface and they each can be a sign of different problems occurring when sanding. Keep in mind that ridges are raised lines on the surface – not to be confused with scratches.

Parallel lines that are close to one another and kind of resemble stairs;

  • Clogged belt
  • Pressure is too high
  • The speed is too low
  • Removing too much stock

Lines that are farther apart and appear in random spots;

  • Belt speed too high or too low
  • Dust extraction is not good
  • Belt is not clean

Waves that run down the workpiece;

  • Clogged belt - from resin or lacquer
  • Damaged abrasive grains

One straight line that runs down the workpiece;

  • Contact roller is damaged
  • Graphite cloth is damaged

Why Are There Scratches On the Surface After Sanding?

Just like raised lines in a workpiece, scratches can appear in different forms as well that can indicate what may be going wrong. To the eye, scratches look the exact opposite of raised lines. When you see scratches, it could be due to a variety of things; the graphite cloth, the rollers, abrasive coating, maintenance issues, etc. 

One long scratch along the workpiece;

  • Graphite cloth is contaminated
  • Pressure beams are contaminated 

Short parallel scratches in a wavy formation;

  • Belt joints are contaminated
  • Abrasive coating may have cracks in it

Scratches that appear in a dashed line along the workpiece;

  • The pressure rollers are contaminated

Why Is It Bad To Have Dust or Static Electricity when Wide Belt Sanding?

An overload of dust or static electricity can cause issues for you such as problems when finishing, lines or scratches, burning of the workpiece, short life span of the belt, etc. It is inevitable to get debris when sanding and removing stock from a material; however, too much dust can start to break down your machine and get stuck to the insides of it. Since heat and friction occurs when sanding, it is a smart move to use a static meter – if it is more than .01 or less than .01 , then you will need to ground your sander. 

Keep in mind that static can also happen a lot more frequently when the weather around you is low humidity. A dust extraction system is ideal to restrict a build up of debris and dust. Make sure that it is properly working to avoid scratches, tracking issues, or loaded belts. If you are noticing that the dust extraction system is not working properly, it may be due to the airflow. 

Why is my Sanding Belt Loading and Burnt?

If loading or burn marks is a problem occurring for you, there may be several things that are wrong in the sanding process. For example, you may be attempting to remove too much stock in one go. Keep in mind that the different grit sizes are specific to an application; 24-40 is best for abrasive planing, 50-80 is for heavy stock removal, 100-150 is for surfacing and cutting, 180-320 is for finishing, and 400 and up is for fine finishing. Make sure you are using the right abrasive backing – cloth, paper, etc – for the application you are doing. 

Another tip to minimize loading or burning is to have different entry points of the belt and the machine because if you continue to sand in only one place on the belt, it will eventually burn and wear out. 

Things that may be causing these issues and that you should check for are resin build up, or glue, getting caught on the belt from the heat and friction. Also, it could be time to switch to a new belt if you have been using one for a while and notice it acting up recently. 

Why Does My Sanding Belt Keep Breaking?

If your sanding belt keeps breaking or has damage – tears, broken or damaged joints, or frayed edges – here are a few things that can determine what's happening.

Tears in the abrasive can be caused from improper tracking: check to make sure it is properly tracking with the machine. Loading can also cause your belt to have damage or break. Like we said before, make sure to use the correct grit sequence, have a clean surface before sanding, and check that the workpiece is the same thickness. Choosing the right backing is also important to avoid breaking your sanding belt. Lastly, a bad joint can be an issue as well. Check to see if your joint can run in different directions. 

Why Does My Sanding Belt Tracking Off the Machine?

If you are noticing your wide belt tracking off the machine, it could be due to tension pressure, the laser eye, or the rollers. Setting the tension pressure properly for the right backing material is key. For cloth backing, use 55 to 65 psi. For paper backing, use 45 - 55 psi, and for polyester backing, use 65 to 85 psi. For the laser eye, you may want to check if it is covered in dust and if so, clean it. Another reason for a belt to not track correctly are rollers that are not parallel. You can fix this with a digital indicator.