In this article we will be talking about one of the most important aspects of a sanding belt – the splice, which Is the point where the sanding belt is joined together to form a “belt.”
There are 5 main types of joints to consider for your operation:
- Butt Splice – This is by far the most common type of joint that you will see and in most cases this is the best option. The butt splice is a splice that will allow your belting operation to be run bi-directionally, meaning it doesn’t matter which way you slide the belt on the machine. It is very common for most sanding belt materials to have an arrow pointing in a specific direction that is essentially an instruction that manufacturer and the customer must abide by if they are making what’s called an “overlap splice” which I will discuss later. The downside with the butt splice is that it is not a 0 tolerance joint however most operations this is not a problem. The normal angle for this butt splice is 67 degrees.
- Sine-Lock Splice – This splice is similar to the butt splice in that the joint joins directly with each other, however this has a wave like or zig-zag pattern going along the joint. This joint is most common in glass fabrication or woodworking operations. This pattern allows the belt to run smoothly, without hinging in either direction. This is very common to see on everything from narrow belts to wide belts and even belts for Hetran type machines.
- Top Skive – For a top skive belt, the abrasive grain near the joint is removed and shaved off using our scuffing machine. This is used specifically on cloth x weight sanding belts where the joint is leaving a scuff on your work piece. This is most common in wood or furniture manufacturing.
- Tape on Top – A tape on top joint is just that, a sanding belt joint with the tape on top of the belt as opposed to on the back side of the sanding belt. This is another form of adding a scuff free joint when sanding across your work piece. This is also very common with woodworking and a special made product
The contact drum sandwiches the belt splice between itself and the wood being sanded so when the thickness of the belt is different than the splice, the rest of the belt is prone to leaving a mark. This is due to the joint passing through the contact point, which is generally about 1/8” of an inch through most timesaver machines & this force pushes the abrasive grains on the belt deeper into the work piece you are sanding. The FIX – Use a belt with tape on top or a top skive. These issues are not extremely common so chances are most of the time the butt splice which is the standard manufacturing procedure for manufacturers will be good enough.
The quickest and easiest method to determine if the chatter marks are caused by the belt splice is to take a lumber crayon (or pencil) and draw on the abrasive belt at the spice point. Then, very lightly, sand a piece of wood and notice where the crayon rubbed off on the wood. If the distance between marks is the same as what the chatter marks in question were, then the splice is to blame.