interior of dryer is scratching clothes
You did not mention the material of the drum so I assume it is not Stainless Steel. 


  Are you sure of the problem - because sometimes the lining around the
  drum at the opening itself wears and allows clothes to get snagged
  between drum and frame.


If it really is the drum you could replace the drum with a new drum, or Replace the dryer with a unit that has a Stainless Steel tub. I know it is a bit more $$ wise but things like knives and such are not going to simply cut into it.