Pneumatic Grinder

Pneumatic grinders, also known as air grinders or die grinders, are handheld powered abrasive devices. They feature an abrasive disk that rotates at high speeds to remove material from the workpiece. Die grinders are powered by compressed air, so they need to be connected to the hoses on the wall to work. This tool can be used for most materials, including the wood for E4 hammer handles and the steel for the hammer hard face. The pneumatic grinders can take some practice, so start on some scrap material and see the tips and tricks below.

Tips and tricks for a good GRind

Don't grind using the center of the disk. Even when your grinder is spinning at a consistent speed, the outside edge of the grinder will be spinning a lot faster than the center. Instead of taking off material, you'll just give your part a weird surface finish.
Don't grind using the edge of the disk. The very edge of the disk is just sandpaper that isn't supported by the grinder. Trying to use this could result in anything from inconsistent grinding to a torn abrasive disk.
Give yourself enough slack on the compressed air hose. It's hard to accurately grind a part when the compressed air reels are trying to pull the grinder out of your hands. Make sure you pull out a bit more than you need and wait until the reel clicks to set the length.
Instead of holding the grinder to the part, use short, swiping passes. Each pass should only remove a little material. This will allow you to control how much material you remove.
Practice on scrap material. Nobody gets the pneumatic grinder right on the first try. Even if you're really good at using the grinder, every material is different. Practice on a separate scrap part or a section of your part that will be removed.
Don't overuse the grinder. When your part is almost done, finish it by hand sanding. Otherwise, you risk taking off too much material, taking your part out of spec. If you're not comfortable using the pneumatic grinder, you might want to stop earlier and hand sand the rest. You can practice the angle grinder another time.
When cutting sparking metals, such as steel, send the sparks away from you. Depending on how you're grinding, using one half of the disk will send sparks toward you, and the other half will send sparks away from you. If you can, pick the side the sends the sparks away and down. Only do this when it is safe to do so.
For cylindrically symmetric parts, grind while your part is on the lathe. This will ensure that your part is even all the way around. You should do this for the hard face of your E4 hammer.