Why doesn't my static friction vs normal force graph pass through the origin?

[SwAnK]

Hey quick question, I did this experiment where I dragged a block across a flat surface with a scale and found the static friction, ehn weight was added to the block and repeated the process. MY question is when graphed with the mass or Fn on the x-axis, and applied force or Fs on the x axis, should it not give a straight line through 0,0 which would be the coeffecient of the static friction?? I am just wondering to know if I am just doing the graph wrong or got messed up results during the experiment.
thanx again

 

[Chestermiller]

If a block is being dragged, static friction is not involved. This involves kinetic friction.