When repairing, I tried to stay close to the original design of the tool. Using a protractor and a ruler, I figured what angle I wanted and scratched it in to the surface. The angle itself doesn't really matter, I just chose something and matched it up to each side. In terms of marking, for this specific tool it was fairly easy to do since I scratched through the caked mud and rust.
From there I took the trowel to the bench grinder in the metal shop.
A few basic rules regarding grinding:
Do Not Wear Gloves. When using a tool that is rotating rapidly, there is always a risk of fabric being pulled in to the machine which will result in serious injury.
Always wear safety glasses and ear protection. When using the grinder, be sure to use the plastic shield on the grinder itself as well as wear safety glasses. It is likely that bits of hot metal will fly in your general direction, especially the eyes. In addition, the grinding room is very small and the grinder is very noisy. I definitely recommend using ear protection to preserve the longevity of hearing.
Use two hands. It is necessary to brace the tool properly in order to prevent it from getting caught on the wheel, or getting pulled in. To prevent injury, use both hands to run the metal across the grinder.
No Aluminum. If aluminum is used on these wheels, it will gunk up the surface and will cause it not to work as well. If you are unsure of what material your tool is, ask a Dream Consultant. If it makes sparks, it's not aluminum!
Grind down the metal on either side up until the line while the tool is aligned horizontal against the wheel. For myself, I allowed a bit of tolerance when dialing down the shape. Inspecting the tool after each pass along the grinding wheel to make sure that the tool was symmetrical. Once the two sides meet at the center of the tool, you should be done! The trowel is now ready to be fully functional in the field.
For a small modification...