Using Your Grinder Safely
The low-speed grinder is ideal for sharpening tools with a reduced risk of overheating their edges. A grinder has other uses, too, such as shaping ferrous metals.
Using a Grinder to Sharpen
The grinder is commonly used to restore or modify the bevel angle when sharpening a tool, such as a plane blade or chisel. It can also quickly remove nicks or other damage. As an example, here are the basic steps you can follow to sharpen or grind a new angle on a chisel with the grinder:
1. Adjust the tool rest to set the desired grinding angle for the tool (Photo 1) You can make a simple angle-setting jig from a piece of cardboard or thin scrap of wood. In the photo, the red line indicates the thickness of the blade, which shows you where the jig should contact the wheel.
Photo 1 – You can use a simple shop-made cardboard jig to set the grinding angle.
2. Turn on the machine and let it reach full speed.
3. It's a good idea to mark the tool's edge with a felt pen to see the progress (Photo 2).
Photo 2 – Color the edge with a marker to monitor the sharpening progress.
4. Place the tool flat on the tool rest and move the tool toward the spinning wheel until it lightly touches the wheel.
5. Move the tool back and forth across the front surface of the wheel while maintaining even pressure on the wheel (Photo 3). Re-apply ink from the felt pen as needed. It’s also good practice the check the edge periodically for square.
Photo 3 – Keep the tool moving to prevent wearing part of the wheel or overheating the tool edge.
6. Keep water close at hand to cool the tool frequently as you grind. Overheating the tool can draw its temper, which means that it will no longer hold an edge and requires grinding past the damage into hardened steel. A change in colour is a sure sign of drawn temper, but damage can occur at a temperature somewhat lower than that which causes a colour change. Work slowly, apply light pressure, and cool frequently.
Photo 4 – Keep water nearby to cool the tool.
7. Check the edge often until the desired amount of material is removed and the bevel comes to a clean apex.
Using Your Grinder Safely
Although the grinder is a small machine, you should be aware of its safety risks. Always wear proper safety gear when operating a machine, and observe all safety advice given in the user manual.
As a reminder, take note of these safety guidelines:
- Always wear proper safety gear, including eye and breathing protection.
- Do not grind on the side of the wheel.
- Always keep the guards in place, except when using a CBN wheel.
- Check bonded wheels periodically for cracking and replace immediately if any are found.
- Unplug the machine before performing any maintenance tasks or changing accessories.