Guide written by:
Didier, Technical manager, Cardiff
From fettling to shaping, a bench grinder can be used for a variety of grinding and sharpening tasks. The type of grinder, the choice of grinding stone and the diameter will depend on its intended use. Read on to choose the right bench grinder to sharpen your tools like a pro.
- Type of bench grinder
- Disc colour
- Twin or single wheel
- Diameter and frequency of use
- Sharpening type
A specific grinder for different types of finish
Firstly, there are different levels of finish in grinding work:
- fettling removes burrs after using grinders;
- deburring is similar but much finer after using hacksaws or filing;
- shaping is a finer grinding operation designed to shape the metal.
You may now understand that a grinding disc used for fettling won't shape your work piece but will eat away at it. Manufacturers are therefore producing tools that offer various possibilities and types of finish.
Twin wheel bench grinder
The twin wheel bench grinder has two grinding discs, each one fixed on the same axis with the same speed. You can then fettle on one side and shape on the other.
Multi-function bench grinder
The multi-function bench grinder has two different systems that can adapt to your needs. The speeds can be the same or different. You can therefore combine the following functions.
- Grinding/ dry sharpening.
- Shaping/ wet sharpening.
- Shaping with a sanding belt/ polishing.
- Deburring/ brushing.
- Other combinations are possible.
The sharpening grinder is specifically for detailed sharpening work. It has one speed and specialised discs.
Twin wheel bench grinders
The colour of the grinding disc indicates the nature of the grinding work
Grinding discs are colour-coded according to the nature of the work. The grit of the grinding disc determines the fineness of the grinding.
They are described below:
- brown is for major fettling work;
- greyish is for grinding ordinary steel;
- white is for sharpening tools;
- green, made from silicone carbide, is for fine sharpening of blades, drill bits and carbide tools.
Although colour is important, it is important to know that most discs are dry sharpening whereas fine sharpening requires a wet sharpener.
Whatever grinding disc you use, remember that its surface must stay straight . For this, there are dressing tools for adjusting your grinding disc. Avoid grinding soft metals which clog up your grinding discs.
The diameter of the grinding disc and power are relative to the frequency of use
Make sure that your choice of disc suits the type of grinding you wish to perform. The choice of material and disc diameter will depend on how often you plan to use it. A diameter of 125mm is sufficient for occasional DIY use. Avoid power ratings under 250W as your grinding disc could jam and cause an accident. A professional will look for longevity and will go for a diameter of 200 to 250mm for long-lasting power of over 500W . Remember that a bench grinder must be fixed. If fixing it to a workbench is a problem, a base will allow you to fix it to the floor and give you space to move around it. A rotating base on some models could be a compromise.
How to choose to your grinding disc for the type of sharpening
Firstly, sharpening is about making a tool sharp. The following steps must be followed:
- Do coarse grinding on a grey disc to shape the cutting edge of the tool.
- Finishing is done on a white disc to refine the cutting edge without damaging it.
- Sharpening is done on a wet sharpener to give the necessary edge without overheating.
- Honing and polishing on leather removes micro-burrs and gives shine to the blade.
It is when you understand the importance of these steps that you realise why all these grinders are needed. But don't get lost in the detail, just get straight to what you need. Just remember that sharpening must be done without heating. A work piece that reaches a high temperature during grinding loses its toughness, hence the need for water sharpeners. A handy trick to avoid heating is to keep a water container close by to cool the piece you're working on.
You might also want to sharpen chainsaw chains and drill bits. Specific grinders exist for these more complex cutting tools.
Manual sharpening: whetstones and knife sharpeners
For those who like to stick to more traditional methods, you can still get a good old grindstone to keep in the back of the drawer. A whetstone has the advantage of being much less cumbersome than a bench grinder. Made up of different grits, it has 2 to 4 sides and may be cooled with water or oil depending on the stone. It also has the advantage of being available in very hard materials, such as silicon carbide. In short, it is unlikely to be a frequently-used tool, although it can come in handy for certain tasks where manual dexterity is needed.
Tool sharpeners and diamond sharpening stones
For seasoned DIYers who are looking for practical tools with high-tech materials, there is a large range of tool sharpeners. The tool sharpener is an easy-to-use tool, made of one or more materials designed to dry sharpen steels. It may come on its own or in a kit. There are also knife sharpeners and diamond sharpening stones for stainless steel.
Bench grinder jigs: guiding the tool for better sharpening
Your choice of grinder must also take safety into account. A bench grinder is a rotating machine that vibrates. Grinding produces heat and sparks that are transferred to the work piece. If used incorrectly, a bench grinder can block or swallow up your work piece. Shaping and sharpening therefore require some dexterity.
To compensate for a relative lack of experience, certain models come with jigs. These guiding elements offer secure positioning and are especially useful for sharpening. Choose them based on the shape of your tool. The jig must be adjustable and robust. These jigs can be adapted to the force of your bench grinder. To finish, please wear eye protection!
Guide written by:
Didier, Technical manager, Cardiff, 8 guides
I spent ten years working in maintenance services, first as a Technician and then as a Head Technician. For eight years, I have perfected the methods and management of subcontracting. Today, I continue my career while I work on technically versatile projects. DIY: I love it. I like having the right tools. Precise work fascinates me, I like working with wood and metal and I do not hesitate to make something myself if it doesn’t exist. In my daughter's room, for example, has a bed built into her desk. My family and neighbors don’t hesitate to ask me for advice or troubleshooting. My experience in home renovation combined with my knowledge of the various building trades allow me to advise on tool choice with pleasure.