Essentially, raised grain is a rough display on the surface of prepared wood where the hard wood is showing slightly above the softer wood. While maintaining this character, they are not actually separated from each other.
Why Does This Happen?
Raised grain happens frequently. This is due to many reasons. The main reason raised grain can occur is because of variations in the wood piece.
Another reason this can occur is when there is moisture in the wood. Moisture in the wood can be determined when you see expanding of shrinking in the wood.
Spring back is another common way to have raised grain appears in the wood piece. This often happens after taking the piece of wood to a machine. The vibrations associated with machining a piece can often dislocate the grains.
Dealing with Raised Grain
1. Check the machines parameters. Checking this before the cut is made can help eliminate this problem.
2. Make Sure tools are sharp.
3. Maintain tools
4. Refrain from shallow cuts.
These are all tips to help reduce the amount of raised grain in the wood you are seeing. All of these tips are a direct result of creating less vibration causing separation of the wood grain.