Replacement blades are expensive,$30 to $40. Why not save some money and sharpen the old one ?
Back before safety razors and during world war II, when steel was scarce, people would resharpen their double edge razor blades on a sheet of glass. I figured why not try it on my Norelco shaver that was leaving my face raw, and it worked, Here is how I did it...
You will need a small brush to clean shaver and heads, also a flat piece of glass ( a mirror or picture frame glass will do).
Step 1: Remove shaver head
Brush out any hair in the body, do not use water.