Flat Hone vs. Twice As Sharp: Which Scissor Sharpening Machine Do You Need?

If you are learning professional scissor sharpening, one of the first equipment decisions you will face is choosing the right scissor sharpening machine. Two names you will encounter frequently are the Flat Hone and the Twice As Sharp machine, often referred to as TAS.

Both are professional sharpening systems, but they are not designed to do exactly the same job. The biggest difference comes down to the type of shear and, more importantly, the geometry of its cutting edge.

A Twice As Sharp machine is primarily designed for sharpening traditional bevel edge shears. A Flat Hone sharpening machine gives the sharpener the control needed to work with convex and Japanese-style shear edges while preserving their curved geometry.

Understanding that difference is fundamental to professional scissor sharpening training.

What Is a Professional Scissor Sharpening Machine?

A professional scissor sharpening machine is equipment designed specifically to restore the cutting edges of scissors and shears. Unlike sharpening a knife, professional shear sharpening requires the sharpener to consider two blades that must work together as a complete cutting system.

The sharpener has to understand much more than how to make an edge sharp. Edge geometry, blade contact, ride lines, tension, set, tip alignment and polishing can all affect how the finished shear performs.

That is especially important with professional hair shears. A barber shear with a traditional bevel edge and a premium Japanese convex shear may look similar to an untrained eye, but they should not automatically be sharpened using the same equipment or technique.

What Is a Twice As Sharp Machine?

The Twice As Sharp scissor sharpening machine is one of the most recognizable sharpening systems in the scissor sharpening industry. You may also hear sharpeners refer to it simply as a TAS machine.

The Twice As Sharp uses rotating sharpening wheels and a clamping system that allows the sharpener to establish and maintain a controlled angle while working the cutting edge.

Its strength is bevel edge shear sharpening.

A bevel edge has a defined flat surface leading to the cutting edge. Because that geometry is fundamentally different from a rounded convex edge, the Twice As Sharp is well suited to many traditional scissors, barber shears and other beveled-edge cutting tools.

For someone entering the sharpening business, understanding what a TAS machine is designed to do is just as important as learning how to operate it.

What Is a Flat Hone Scissor Sharpening Machine?

A Flat Hone approaches shear sharpening differently.

Instead of relying on the same wheel-and-clamp approach used for a traditional bevel edge, a Flat Hone provides a flat abrasive surface that allows a trained sharpener to work and polish the outside surface of the shear with greater control over the blade's geometry.

This becomes particularly important when sharpening convex edge shears.

A true Japanese-style convex or Hamaguri edge does not have one simple flat bevel. Its outside surface transitions through a radius toward the cutting edge. Preserving that geometry requires understanding the shape of the blade and controlling how material is removed.

If you want a deeper understanding of that geometry before learning the sharpening process, our Convex Edge / Japanese Edge / Hamaguri Theory Module explains the foundation behind true convex shear design.

Flat Hone vs. Twice As Sharp: What's the Difference?

The simplest way to understand the difference is to start with the edge you are trying to sharpen.

Feature	Twice As Sharp	Flat Hone
Primary Strength	Bevel edge sharpening	Convex edge sharpening
Abrasive System	Sharpening wheels	Flat abrasive pads/discs
Typical Edge Geometry	Flat, defined bevel	Curved convex/Hamaguri geometry
Common Application	Traditional scissors and beveled shears	Professional salon and Japanese-style convex shears

This does not mean that simply owning the correct scissor sharpening machine makes someone capable of sharpening every shear. The machine is only the tool. The sharpener still needs to correctly identify the edge and understand how that edge was designed to function.

Twice As Sharp for Bevel Edge Shear Sharpening

The Twice As Sharp machine makes sense when the shear has a traditional bevel edge that needs to be restored at a controlled angle.

Beveled edges have a clearly defined flat surface. This makes them fundamentally different from convex edges, where the outside of the blade follows a curved radius toward the cutting edge.

Learning bevel edge shear sharpening therefore requires learning to identify the existing geometry before removing steel.

The abrasive wheels used on the TAS are another important part of the process. Different wheels and abrasives perform different jobs during sharpening, finishing and polishing.

Our Sharpening Wheels for Twice As Sharp Training Module focuses specifically on understanding the wheels used with this type of sharpening system.

Flat Hone for Convex Edge Shear Sharpening

Professional salon shears introduce another level of complexity because many use convex, semi-convex or Japanese-style edges.

With a convex shear, the goal is not simply to grind a new flat angle onto the blade. The sharpener needs to understand and preserve the radius that forms the outside geometry of the edge.

This is where the Flat Hone scissor sharpening machine becomes especially important.

The Flat Hone allows the trained sharpener to work through the blade's geometry and polishing process while maintaining control over the surface being sharpened.

The abrasive system itself also matters. Grit selection and progression affect material removal, refinement and final finish. Our Sharpening Pads for Flat Hone Training Module focuses specifically on the abrasive pads used in Flat Hone sharpening.

Can You Sharpen Convex Shears on a Twice As Sharp Machine?

This is an important question because the answer involves more than whether a machine can physically remove metal from a blade.

A professional sharpener should ask a different question: Will the sharpening method preserve the edge geometry the manufacturer intended?

A true convex edge has a curved outside surface rather than a single flat bevel. Treating that geometry like an ordinary bevel can alter the shape of the edge.

That is why professional sharpeners need to identify the edge before deciding which machine and sharpening process to use.

Our Edge Types Training Module covers convex, semi-convex, beveled and serrated edges and explains why recognizing the edge type is one of the first steps in professional shear sharpening.

Which Scissor Sharpening Machine Should You Learn First?

There isn't one machine that eliminates the need to understand the other sharpening systems.

If your work involves traditional beveled scissors and shears, understanding the Twice As Sharp system is valuable. If you intend to service professional salon shears, particularly premium convex and Japanese-style shears, understanding Flat Hone sharpening becomes extremely important.

A professional sharpener who wants to service a broad range of scissors should understand what both systems are designed to accomplish.

The most important lesson is this: identify the shear and its edge first, then choose the sharpening process.

Scissor Sharpening Training Is More Than Learning a Machine

Buying a scissor sharpening machine is relatively easy. Learning how a professional shear actually works takes considerably more knowledge.

A sharpener needs to understand edge types, convex geometry, ride lines, tension systems, set, alignment, abrasives, polishing and how both blades interact after sharpening.

For example, the Ride Lines Training Module explains a critical part of shear geometry that can affect blade contact and cutting performance. A sharp edge alone does not guarantee a properly functioning shear.

This is why professional scissor sharpening training should teach the entire cutting system rather than simply teaching someone how to operate a machine.

Learn Flat Hone and Twice As Sharp Scissor Sharpening

The Shear Fanatic Sharpening Machines Training Module covers the differences between Flat Hone and Twice As Sharp sharpening systems and helps sharpeners understand where each machine fits into professional shear service.

This machine training works alongside dedicated modules covering Flat Hone abrasive pads, Twice As Sharp sharpening wheels, convex edge theory, edge identification and the other technical elements involved in professional shear sharpening.

Whether you are starting a sharpening business, adding professional hair shears to an existing sharpening service, or trying to improve your understanding of the equipment you already own, knowing why you are choosing a particular sharpening machine is just as important as knowing how to turn it on.

Explore the Complete Professional Shear Sharpening Training Program →

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Frequently Asked Questions About Scissor Sharpening Machines

What machine is used to sharpen professional scissors?

Professional sharpeners use different machines depending on the type of scissors and edge geometry. Two common systems are the Twice As Sharp machine for traditional bevel edge sharpening and Flat Hone systems for professional convex and Japanese-style shear sharpening.

What is a Twice As Sharp machine?

Twice As Sharp, commonly called TAS, is a professional scissor sharpening system that uses sharpening wheels and a controlled clamping system. It is particularly well suited to traditional bevel edge scissors and shears.

What is a Flat Hone scissor sharpening machine?

A Flat Hone uses a flat abrasive surface and allows a trained sharpener to control the sharpening and polishing of professional shear blades. It is especially important when working with convex and Japanese-style shear geometry.

What is the difference between a Flat Hone and Twice As Sharp?

The primary difference is the sharpening system and the edge geometry each is best suited to service. Twice As Sharp excels at traditional beveled edges, while Flat Hone equipment provides the control required to preserve and sharpen convex shear geometry.

Is Twice As Sharp good for sharpening hair shears?

It depends on the shear. A Twice As Sharp machine can be appropriate for hair shears with traditional beveled edges. Premium salon shears with true convex or Japanese-style edges require a sharpening process that preserves their curved edge geometry.

Do I need a Flat Hone to sharpen convex shears?

A Flat Hone is the professional sharpening system commonly used for true convex and Japanese-style salon shears because it allows the sharpener to work with and preserve the curved outside geometry of the blade.

Can I learn scissor sharpening without buying a machine first?

Yes. In fact, learning edge identification, shear construction and the differences between sharpening systems before purchasing equipment can help you understand which machine is appropriate for the type of sharpening work you intend to perform.

Where can I learn professional scissor sharpening?

Shear Fanatic offers a complete professional shear and scissor sharpening training program with individual training modules covering sharpening machines, convex edges, edge types, abrasives, ride lines, tension, alignment and other essential professional sharpening skills.

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