It depends on the angle of the shear blade. Professional PCB shears cut almost all the width at once so there is very little twisting of the material before it is cut. Sheetmetal shears or laminate flooring cutters cut more gradually (to reduce the required force) and will leave visible delamination a millimeter or so in from the edge.
Even with a professional shear the edge is not as nice, smooth, and square as a milled or sawn edge, but perfectly adequate for most applications. I always used to sand or file them to remove any rags.
ST
On Sat, Jan 23, 2016 at 12:16 PM, kbyrne10@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:
Does a brake prevent cracks as my diamond tip saw blade does and is safe while using the proper push sticks and feather boards as I am always looking for new ways to do any job.