When it comes to sharpening chisels or plane irons there are two warring camps as to how to grind them. One group believes the angle should be ground flat. (This group includes those with traditional Japanese chisels and plane irons and those who do not own grinding wheels.) The other group believes you should use a grinding wheel that leaves a concave surface. They say it is easier to hone because you have two surface edges to align the blade on a stone to sharpen them. The flat grinders use some sort of angle fixture and generally add a second, steeper angle/. They call it a micro bevel and it makes touching up the edges very quick. The wheel grinder say that two angles is a lot of work.
I realized that the wheel grinders do have two angles; the grind angle and the actual angle at the tip of the blade.
So I wrote this little HTML app to allow you to calculate the actual angle given the grind angle, wheel diameter, and tool thickness. Just follow the instructions to unload it.
Step 1: Grab File and Uncompress It
Place to included zip file onto your computer and unzip it.
Go into the new folder and open GrindCal.html. The app will open. You may want to hide this folder someplace and place a shortcut to the app someplace handy.
Step 2: Example
I have a chisel that is 1/8" thick. I entered 1/8 into the proper window and the app calculated the value to be 0.125.
I entered a wheel diameter of 8" and a grind angle of 25 degrees. ( You can use metric as long as it it used for both the wheel diameter and tool thickness. The angle must be in degrees.)
The app calculated the actual angle to be 22.8 degrees so I am comfortable grinding a flat angle of 23 degrees and honing a micro bevel of 25 degrees.