How to Sharpen Tools with a Bench Grinder — Complete Guide

A sharp tool is a safe tool — and a pleasure to use. A blunt chisel requires more force, is harder to control, and produces a poor finish. A sharp one glides through wood cleanly with minimal effort. The bench grinder is the fastest and most effective way to restore a sharp edge to almost any tool. Here's how to do it properly.

Why Use a Bench Grinder for Sharpening?

Hand sharpening on waterstones is a valuable skill — but it's slow. For restoring a badly damaged or heavily blunted edge, a bench grinder removes material far faster than any hand method. Once the correct bevel is established on the grinder, finishing on a whetstone or strop takes just seconds.

The TEH TBG20035 350W 200mm bench grinder is ideal for tool sharpening — with dual 200mm wheels, 2840 RPM, and a stable 12kg bench-mounted construction that stays firmly in place during use.

Before You Start — Wheel Dressing

Before sharpening anything, check the condition of your grinding wheel. Over time, grinding wheels become glazed (smooth and shiny) or loaded (clogged with metal particles). A glazed or loaded wheel grinds inefficiently and generates excessive heat.

Use a wheel dresser to restore the wheel surface:

• Hold the dresser firmly on the tool rest
• Apply it to the spinning wheel with light pressure
• Move it slowly across the wheel face
• The wheel surface should appear clean, slightly rough, and uniform

Always dress the wheel before a sharpening session for best results.

The Golden Rule — Control the Heat

The biggest risk when grinding tools is overheating — also called drawing the temper. If a tool edge turns blue or straw-coloured during grinding, the steel has been overheated and the hardness has been destroyed. That section of the edge will never hold a sharp edge again.

How to prevent overheating:

• Keep a container of water next to the grinder
• Dip the tool in water every few seconds during grinding
• Never grind for more than 5-10 seconds without cooling
• If the tool feels warm to the touch — it's already close to overheating
• Use light pressure — heavy pressure generates more heat
• Keep the tool moving — never hold it stationary against the wheel

Sharpening Chisels and Plane Blades

Chisels and plane blades are the most common tools sharpened on a bench grinder. The bevel angle is typically 25-30° for most woodworking chisels.

Step by step:

1. Set the tool rest to approximately 25-30° — most grinders have an adjustable tool rest
2. Hold the chisel flat on the tool rest with the bevel facing the wheel
3. Apply light pressure and move the chisel smoothly left and right across the wheel face
4. Lift the chisel and dip in water every 5 seconds
5. Check the bevel regularly — you're looking for a consistent, flat bevel across the full width
6. When a wire edge (burr) appears on the flat face of the chisel the primary bevel is complete
7. Move to the fine wheel for a cleaner finish
8. Remove the wire edge by honing on a flat whetstone or leather strop
9. Test sharpness by shaving arm hair — a truly sharp chisel shaves cleanly

Common mistakes:

• Grinding hollow — holding the tool at a consistent angle prevents this
• Overheating — always cool frequently
• Uneven bevel — keep the tool moving side to side

Sharpening Drill Bits

Sharpening twist drill bits on a bench grinder takes practice but is a valuable skill — a sharp drill bit cuts cleanly, requires less pressure, and produces less heat.

Step by step:

1. Examine the drill bit — identify the cutting edges and the relief angle behind them
2. Hold the drill bit at approximately 60° to the wheel face
3. Apply very light pressure to one cutting edge
4. Rotate the bit slightly as you grind — this creates the relief angle behind the cutting edge
5. Cool frequently
6. Repeat for the other cutting edge — match the angle precisely
7. Check that both cutting edges are the same length — uneven edges cause the drill to wander

For beginners a drill bit sharpening jig makes this much easier — it holds the bit at the correct angle automatically.

Sharpening Garden Tools

Garden tools — spades, hoes, lawn edgers, and secateurs — benefit enormously from sharpening. A sharp spade cuts through soil and roots far more easily than a blunt one.

Step by step for spades and hoes:

1. Clamp the tool securely or hold it firmly against the tool rest
2. Hold at the original bevel angle — typically 20-25° for most garden tools
3. Grind with smooth, even strokes along the cutting edge
4. Garden tools don't need to be razor-sharp — a good working edge is sufficient
5. Remove any nicks or chips from the edge before finishing

For secateurs and pruning shears:

• Sharpen only the bevelled face — never the flat face
• Use the fine wheel for secateurs
• Maintain the original angle precisely

Sharpening Knives

A bench grinder can sharpen knives quickly — but requires care to avoid overheating thin blades.

• Use the fine wheel only for knives
• Keep the blade moving constantly
• Cool every 2-3 seconds — knife blades are thin and heat up quickly
• Maintain the original bevel angle — typically 15-20° for kitchen knives
• Finish on a whetstone for a truly sharp edge

What the Two Wheels Are For:

Always start on the coarse wheel for damaged or heavily blunted tools, then finish on the fine wheel. For lightly blunted tools that just need touching up, the fine wheel alone is often sufficient.

Safety — Non-Negotiable:

• Always wear safety glasses — grinding throws sparks and metal fragments
• Ensure the grinder is securely bolted to the bench
• Keep the tool rest within 3mm of the wheel
• Never grind on the side of the wheel — only the face
• Never use a damaged or cracked wheel
• Allow the wheel to reach full speed before applying the tool
• Keep fingers away from the wheel — use the tool rest to support the workpiece

Browse the TEH TBG20035 200mm Bench Grinder and our full workshop tool range at tehtools.co.uk