Newbie.. ok to practice sharpening on these knives?

[ChapmanPreferred]

For practice knives, I go down to my local "rescue mission" Thrift Store. In our town, they have "Sharp Knives" labeled with $0.25 on the drawer (so $0.27 including PA tax). I look for old carbon steel knives and knives made in Japan which seem to have steel that is easier to sharpen then most US or Chinese produced stainless steel blades in the same drawer. The blades are very thin, so you have less metal to remove before you even get started. Most are in the 4" to 8" carving or chef knife catagories. It is usually pretty easy to identify the carbon steel knives due to the bluish/grayish/blackish patina on the entire blade and the knives made in Japan usually have a pretty clear stamp or engraving near the handle. I also watch yard sales in the spring and summer, but that may not be everyone's bag. I picked up three MAC chef knives of different lengths for free because the owner said they were "Dull as sin". Which was not an issue for me.